RAID Vs. JBOD Vs. Standard HDDs 555
Ravengbc writes "I am in the process of planning and buying some hardware to build a media center/media server. While there are still quite a few things on it that I haven't decided on, such as motherboard/processor, and windows XP vs. Linux, right now my debate is about storage. I'm wanting to have as much storage as possible, but redundancy seems to be important too." Read on for this reader's questions about the tradeoffs among straight HDDs, RAID 5, and JBOD.
At first I was thinking about just putting in a bunch HDDs. Then I started thinking about doing a RAID array, looking at RAID 5. However, some of the stuff I was initially told about RAID 5, I am now learning is not true. Some of the limitations I'm learning about: RAID 5 drives are limited to the size of the smallest drive in the array. And the way things are looking, even if I gradually replace all of the drives with larger ones, the array will still read the original size. For example, say I have 3x500gb drives in RAID 5 and over time replace all of them with 1TB drives. Instead of reading one big 3tb drive, it will still read 1.5tb. Is this true? I also considered using JBOD simply because I can use different size HDDs and have them all appear to be one large one, but there is no redundancy with this, which has me leaning away from it. If y'all were building a system for this purpose, how many drives and what size drives would you use and would you do some form of RAID, or what?
Two words: RAID 0 (Score:5, Funny)
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Actually, it's 59.5449999%. So it's 5 nines no matter how you look at it.
Re:Two words: RAID 0 (Score:5, Insightful)
I.e. 3 500 GB drives in a RAID 5 doesn't give you 1.5 TB. (RAID 0 dose that). With RAID 5 you only get 1 TB.
Nuh-Uh (Score:5, Funny)
Raid 0 won't protect you, man!
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Perhaps a Post-It note on the monitor to remind myself.
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Re:Nuh-Uh (Score:5, Funny)
Freaky, that's the exact excuse I used for failing my CS binary course
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Chuck Norris
Man, Raid 10 + Raid 5 + Offsite backups can't save you now!
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Re:Two words: RAID 0 (Score:5, Funny)
For the love of God and all that's holy will someone mod this 'Funny' instead of Informative? I get the joke, but there's always somebody who won't!
(Then again... maybe people who won't oughta make a 10 disk RAID 0, hell mod it insightful sucka!)
Re:Two words: RAID 0 (Score:5, Funny)
I would, of course, be using a different 10-drive raid-0 pack to record the tragedy -- but I'd be safe because it's my disk pack (which makes it impervious to catastrophic failure).
Re:Two words: RAID 0 (Score:5, Funny)
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Or... get an Intel motherboard with Matrix Raid chip, it'll allow you to add more drives to an array or increase it's size when you increase the storage space.
However... not using RAID would make it more flexible for you, wheter it's worth it is up to you. Personally I'd go for RAID 5 (I have done the same at home).
Re:Two words: RAID 0 (Score:4, Funny)
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Re:KISS it (Score:5, Informative)
3ware [3ware.com] made some pretty good cards.
Re:KISS it (Score:5, Insightful)
But the minute or so of uptime you get by not having to power down the computer is more than made up when the controller chip on your beautiful RAID controller sizzles. Using Linux software RAID lets you plug the drive(s) into another computer of a completely different chipset, boot up, and continue operations as though nothing had ever gone wrong. IMHO, this is far preferable to the effective lock-in presented to you by hardware controllers.
For me, it's all 100% software RAID 1.
Re:KISS it (Score:5, Informative)
Eh?
LVM [wikipedia.org] and RAID [wikipedia.org] are orthogonal solutions, and don't do the same thing. LVM will let you make a single larger partition out of a number of real partitions, and before anyone says that's the same as RAID0, I should point out that RAID0 is not a real RAID level (as it has no redundancy). The circumstances for failure for LVM and RAID0 (JBOD too) are basically the same - if one part fails, you will quite possibly lose the whole lot.
As for hardware RAID, I would not necessarily recommend that either, as it moves the single point of failure without resolving the problem. Replacing a broken controller with something compatible some years down the road can prove impossible, especially with onboard controllers. There's also the fact that a number of RAID controller cards are buggy and others do most os the work in software drivers anyway! Performance is also no longer a reason to use a pure hardware RAID solution, especially now that multi-core machines are available cheaply.
Hot-swap is still someting that requires a good hardware solution, but that's about it. Good (and well supported) RAID products cost good money too, and for most of us it's just not worth doing - better to use software RAID, buy more RAM, and pocket the rest.
-- Steve
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Especially when you've actually tried hot swapping in a few such devices and seen that the RAID thingie is mostly dead in the water for ages while it's trashing itself trying to rebuild the missing bits. In every such case from what I've seen, in real life, with RAID 0|5, while you don't lose any data with a disk failure, you certainly lose availability. In the best of cases you can only get a trickle of data from the
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It's vitally important that if you go the hardware RAID route then you get the right card. Do not get fake RAID cards, and check your Linux compatibility if you run Linux. If you get the right card than it's infinitely more preferable than software RAID, because there's so much less to do. The OS sees the drive as one big disk, and you can use hotswap cages much more reliably. D
Re:KISS it (Score:4, Informative)
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By the way, does anyone have recommendations on 4-port SATA controllers?
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It (RAID1) can be, with some caveats. Just 'fail' one of the mirrors and take it off site (same as you would a tape).
I'm sure it works very nicely in some situations.
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If you use fake RAID [linux-ata.org], then you basically have no guarantee that the on disk format will be the same from one motherboard to the next, even within a particular vendor.
I would suggest not using fake RAID if you have any intentions of moving the disks to a new system (or really, at all... the only potential plus is Windows compatibility). Fake RAID uses a vendor-specific proprietary on disk format, and is typically slower than both software RAID, and hardware RAID.
RAID in any form has minimal impact on dis
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3ware makes a fine hardware raid card that have between 2 and 16 or more SATA ports on them. Of course the costs go up with more ports. Adaptec has some also but I had problems with the last one I used and according to the Internet I wasn't alone. If I remember right, with a hardware raid, there is information about the raid configuration and all t
Do some research first? (Score:5, Informative)
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While Solaris might be a dirty word among the Slashdot crowd, if all the OP needs is a way to store a bunch of files, ZFS is an excellent solution. Check out http://www.opensolaris.org/os/community/zfs/whatis
Then, if you're still not convinced how appropriate ZFS might be for a so
Re:Do some research first? (Score:5, Funny)
Nonsense! Everything you need to know is in the RAID 5 song:
(My friend Rich actually came up with this. I like him too much to slashdot him, though.)
Duh (Score:5, Insightful)
That said, RAID is not a replacement for proper backup. RAID is just a first line of defense to avoid downtime.
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A good point. Consider, though, that most people don't run terabyte-size tape backup at home. It's not like it's business critical data, so RAID-5 is probably sufficient.
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Re:Duh (Score:5, Funny)
Hell yeah.
Cool but untested tech is always best recommended to others before you try it. Preferably LOTS of others.
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RAID-5 is "good enough" for home use though. If you're paranoid then build a second box that just backs up the first via rsync or rdiff-backup. The second box doesn't necessarily even have to have a RAID array, you could LVM a bunch of disks together. If the backup array dies then oh well, just install a new drive and rsync from your production server again. Personally I don't even bother to b
Re:Duh (Score:4, Insightful)
RAID is just a first line of defense to reduce downtime.
Don't worry about losing your media files (Score:5, Funny)
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Design for today. (Score:2, Interesting)
That being said, mirroring might be the easiest solution to upgrade, but you'll sacrifice speed and space.
If you want speed and redundancy, you'll have to go with something like RAID 5 or RAID 10 and just have a painful upgrade in the future.
I would use (and do use) linux software raid (Score:2, Informative)
RAID (Score:2, Informative)
It depends (Score:2, Informative)
Is Google broken today? (Score:2, Insightful)
Yes... Duh....
And the way things are looking, even if I gradually replace all of the drives with larger ones, the array will still read the original size. For example, say I have 3x500gb drives in RAID 5 and over time replace all of them with 1TB drives. Instead of reading one big 3tb drive, it will still read 1.5tb. Is this true?
Yes... Fucking duh.... Have you even read the RAID 5 Wiki article? [wikipedia.org]
I also considered using JBOD simply becau
You can mix raid drive sizes, with planning. (Score:4, Interesting)
I had 4 300GB drives, and 2 200GB drives.
I broke them up into 100GB partitions, and layed out the RAID arrays:
A1 = [D1P1 D2P1 D3P1 D5P1]
A2 = [D1P2 D2P2 D4P1 D6P1]
A3 = [D1P3 D3P2 D4P2 D5P2]
A4 = [D2P3 D3P3 D4P3 D6P1]
Then I concatenated the arrays together, giving a little less than 1.2 TB of space from 1.6 TB of drives; if I had just RAID'd the 4 300 gig drives, and mirrored the 200's I would have only had 1.1 TB available, and the drive accesses would be imbalanced.
I could also grow the array, since it was built as concatenated, so later when I got 4 400GB drives I raided them then tacked them on for 2.4 TB total.
Re:Is Google broken today? (Score:5, Funny)
Not hard at all... [killsbugsdead.com]
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X-RAID and an Infrant ReadyNAS NV+ = gold. These NAS were built by people who actually thought about the home or prosumer's needs and built something that addressed it, instead of "here's what we offer, take it or leave it".
(However, we should note that Netgear has bought Infrant, so it's the Netgear ReadyNAS now.)
Get what you need for *NOW* not for later (Score:5, Insightful)
With computers, the stupidest thing you can do is spend extra money to prepare for your needs for tomorrow. Buy for what you need now, and by the time you outgrow it, things will be cheaper, faster and larger.
By the way RAID 5 is a pain in the ass unless you have physical hotswap capability, which I highly doubt.
Re:Get what you need for *NOW* not for later (Score:4, Interesting)
With recent kernels, you can hotswap drives on nvidia sata controllers (common onboard). I believe several other chipsets had support for this added in recent kernels too. Then you can swap drives live and rebuild as needed.
One more important note - if you're using more than about 8 drives (I personally recommend 6), I would use raid 6 instead of 5. You often get read errors from one of your "good" drives during a rebuild after a single drive failure. Having a 2nd parity drive (that's what raid 6 gives you) solves this problem.
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500 GB isn't that much space any more. If he's thinking of making an HDTV MythTV box, for instance, full-res HDTV streams will require a lot of space to store in real-time. It would probably be too computationally intensive to recode them into MPEG4 on the fly.
SCRUB your arrays! (Score:3, Insightful)
This is what you do: buy 2 drives exactly the same size and mirror them. End of story.
NO! That's NOT the end of the story. You need to do what is called "scrubbing" the array periodically, because drives "silently" fail, where areas become unreadable for various reasons. Guess when one usually discovers the bad data? When one drive screeches to a halt, and you confidently slap in another and hit "rebuild". Surpriiiiiiiiise.
You can do it a variety of ways. The most harmless is probably to run a re
Re:SCRUB your arrays! (Score:4, Informative)
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RAID 5 is damned easy. (Score:5, Interesting)
Until another few years go by and you want to buy more storage. Then you're basically stuck with doubling it, clumsily -- or migrating away and essentially throwing out the old drives.
RAID 5 is better in the short run. Even with a three disc array, you're getting more storage for your money, and you can always restripe it onto a fourth disc.
It's not all porn, and some of it is high def, in h.264. And I don't even edit videos, I just watch 'em.
That is true. However, I would fill a terabyte easily, and right now, I'm guessing it's cheaper to buy three 500 gig drives than two 1 tb drives.
You highly doubt he's got SATA?
The one thing I will say is, either have another disk (even a USB thumb drive) to boot off of, or do some sort of RAID1 across them. You almost certainly want software RAID on Linux, and you don't want to try to teach a BIOS to boot off of your array.
Wait a sec... (Score:4, Funny)
Why not the "windows XP vs. Linux" bit? Do you want 100 responses or 1000?
Media Server? (Score:5, Funny)
Re:Media Server? (Score:5, Funny)
Only if you make all your network file shares pubic.
Linux, raid5, LVM on top, can use extra capacity (Score:5, Informative)
If you buy 1TB drives further down the road, here's what you do- With each disk, create a partition identical in size to the partitions on the smaller disks, then allocate the rest of the space to a second partition.
Join the first partition of the disk to the existing RAID set. Let it rebuild. Swap the next drive, etc. etc. Then once you've done this switcharoo to all the drives, create another raid set using the 2nd partition on your new disks--call it
Take that
Just be sure that any replacement drives you have to buy... you must partition them out similarly. I'd recommend pulling back on the partition sizes a bit, maybe 5%, to account for any size differences between the drives you bought right now and some replacement drives you may purchase later on which might be slightly lower in capacity (different drive manufacturers often have differing exact capacities).
depends on the raid implementation (and level?) (Score:2, Informative)
The "Raid 5 can't do what I heard" isn't quite what's going on, again, depending on the implementation. Most raid cards I've used allow you to add drives to the
Linux, RAID 5, md (Score:5, Informative)
Go Linux. The Linux MD driver allows you to control how you RAID- over disks or partitions. there are advantages. We will discuss.
First, don't get suckered into a hardware RAID card. They are *NOT* really a hardware card- they rely on a software driver to do calculations on your CPU for RAID5 ops. Software RAID is JUST AS FAST. Unless you blow the big bucks for a card with a real dedicated ASIC to do the work, you're fooling yourself.
Now, you want to go Linux. By using the md driver, you can stripe over PARTITIONS, and not the whole disk. By doing this, you can get MAXIMUM storage capacity out of your disks, even in upgrades.
Say you have 3 500GB disks. You create a 1TB array, with 1 disk as parity. On each of these disks is a single partition, each the size of the drive. Now, you want to upgrade? SURE! Add 3 more disks. Create three partitions of EQUAL size to the original, and tack it on to the first array. Then, with the additional space, you can create a WHOLE NEW array, and now you have two seperate RAID5's, each redundant, each fully using your space.
Another advantage with MD is flexibility. In my setup, I use 5x 250 drives right now. On each is a 245GB partition, and a 5GB partition. I use RAID1 over the 5's, and RAID5 over the rest. Why? Because each drive is now independently bootable! Plus, I can run the array off two disks, upgrade the file system on the other 3, and if there's a problem, I can always revert to the original file system. So much flexibility, it's not even funny.
I recommend using plain old SATA, in conjunction with SATA drives, and just stick with the MD device. For increased performance, watch your motherboard selection. You could grab a server oriented board, with dedicated PCI buses for slots, and split the drives over the cards. Or, you can get a multiproc rig going, and assign processor affinity to the IRQ's- one card calls proc 1 for interrupts, the other card calls proc 0. If you have multiple buses, then performance is maximized.
The last benefit? Portability. If your hardware suffers a failure, then your software RAID can move to any other system. Using ANY hardware RAID setup will require you to use the EXACT same card no matter what to recover data. Even the firmware will have to stay stable or else your data can be kissed goodbye.
Windows? Forget about it.
Good luck!
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Re:Linux, RAID 5, md (Score:4, Informative)
I recommend Gentoo to do this with. Other distro's dont include the latest mdadmtools required to manage and migrate RAID5 md devices. Ubuntu is catching up, I believe.
Here are some places to start:
http://gentoo-wiki.com/HOWTO_Gentoo_Install_on_So
http://www.gentoo.org/doc/en/gentoo-x86+raid+lvm2
http://linas.org/linux/Software-RAID/Software-RAI
http://linas.org/linux/raid.html [linas.org]
http://evms.sourceforge.net/ [sourceforge.net]
http://www.tldp.org/HOWTO/Software-RAID-HOWTO.htm
Re:Linux, RAID 5, md (Score:4, Interesting)
I have 6 320 GB disks. The /boot partition is RAID 1, mirrored across all 6 (yes, 6) devices, and grub is configured so that I can boot from any one of them. The rest of the partitions are RAID 6, with identical allocations on each disk.
There's a RAID HOWTO for Linux: it tells you everything you need to know about setting it up.
Re:Linux, RAID 5, md (Score:4, Informative)
Higher RAID-levels are not always THE ultimate solution and depending on your solution you might just have to go for a non-secure RAID level (RAID0) for large media storage with nightly snapshotting to your backup device. Usually it's not all that bad to lose a single day worth of data and if it is for these applications, use RAID10 or so. I do it as follows: get media on RAID0 (HD streams are large and fast on 10k drives) and then as soon as job is done, I copy it to the storage area which is RAID5 on cheap SATA storage and then a nightly copy to an offline backup station (HW-RAID5 with ATA100) of the data I want to keep.
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What's rather humorous about this statement is that ultimately, all firewalls are implemented in software. What is firmware, again?
There are three different implementations of RAID on PC class hardware- software RAID, fake-hardware RAID, and hardware RAID.
When I said that software is just as fast, I'm comparing it to fake RAID cards, cost under ~$200 US. These cards rely on driv
How the hell did this make the front page? (Score:4, Insightful)
This place has really gone downhill. I thought Firehose was supposed to stop stuff like this, not increase it!
Anyways, just to be slightly on topic: there's no one answer to this question. It depends on your budget, your motherboard, your OS, and, most importantly, your actual redundancy needs. This kind of thing is addressed by large articles/essays, not brief comments.
Bad assumption (Score:2, Informative)
Risk what you can do without (Score:2)
I'm a student and I do not have the money for redundant storage.
I rsync my documents and pictures over the two drives and burn my favourite movies to DVD. I use ffmpeg to turn DVDs into Xvids and oggenc to turn flacs into ogg q5s.
If I lose one of the harddrives; that's life.
So for those who do not have the luxury that the poster has; make sure that you backup what is really important and risk what you
What for? (Score:2)
If y'all were building a system for this purpose, how many drives and what size drives would you use and would you do some form of RAID, or what?
For what purpose?! You haven't said word one about how this storage will be used. What is it for? Email back end, shared file systems, RDBMS (OLTP or OLAP), streaming loads, D2D backup, etc. Define your use case, please! Post after post on this topic and not one of you ever think to specify what the @!%*$ it is you're trying to do.
Agonizing over the ability to incrementally upgrade an array is a sure sign you have cost at the very top of your list of concerns, with everything else far below. Learn ab
Planned obsolescence (Score:4, Insightful)
Here's the way I do it (for a home storage server, not a solution for business-critical stuff):
Examine current storage needs, and forecast about two years into the future.
Build new server with reliable midrange motherboard, and a midrange RAID card. These days you could do with a $100-$300 four-port SATA card, or two.
Add four hard disks in capacities calculated to last you for two years of predicted usage, in RAID 5 mode. Don't worry about brand unless you know for a fact that a particular drive model is a lemon.
Since manufacturer's warranties are about one year, and you may have difficulty finding an unused drive of the same type for replacement, buy two more identical drives. These will be your spares in the event of a drive failure.
When the two years are up, you should be using 80 to 90 percent of your total storage.
At this point, you build an entirely new server, using whatever technology has advanced to at that time.
Transfer all your files to the new server.
Sell your entire old storage server along with any unused spare drives. A completely prebuilt hot-to-trot RAID 5 system, with new matching spare disk, only two years old, will still be very useful to someone else and you can recoup maybe 30 to 40 percent of the cost of building a new server.
Lather, rinse, repeat until storage space is irrelevant or you die.
slow news day? (Score:2)
As to the poster's question: read the fucking manual, kid.
RAID 5 is for cheapskates (Score:2)
2x500GB drives in a RAID 1 (for peace of mind). Then double that in a RAID 0 stripe (for speed). That's 4 drives per TB. Then use a decent file system, like ZFS, to chain your RAID 1+0 clusters into a single volume 1TB at a time.
Whatever you choose t
RAID5 and disk size (Score:2)
However, the better approach would be to recreate the array on disk upgrades. After all for any kind of reliability, you need backup anyways. RAID is not a replacement for backup!
More info please (Score:2)
At 1TB, it is still gonna be pretty hard to fill this with DIVX encoded movies. I guess though, if you need more space, do a 0+1. Meaning a redundant array of a data-striped set.
If you are talking about some sort of seriously whacked out array of like some Blu-Rays or HDDVDs or some crazy thing like that....then i wou
Go RAID 5 BUT with real hardware.... (Score:3, Insightful)
Again, doing it correct up front takes care of upgrade options down the line. It also gives you room to do monster sized volume if you ever need that much space (8 disk array). Most of these RAID solutions are also OS independent, so if you want dual boot, the volume would be recognized by Windows, Linux, Unix, BSD, etc., and you are also not dependent on using the exact same motherboard if you motherboard dies or wants to be upgraded (you would lose all your data if you use the built in RAID on the motherboard when changing to a new motherboard other then the exact same model).
These better cards also can be linked together (i.e. you always get a second card assuming your motherboard has a slot for it, and add more disks to the array that way as well).
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I haven't seen a consumer level motherboard that has real (hardware) RAID. It's all software RAID with a fancy driver & BIOS support to allow Windows to boot.
I'm not s
One acronym - ZFS (Score:3, Interesting)
Your data should be perfectly safe, with raidz2 can lose up to 2 drives, without data loss.
The simple answer is (Score:3, Interesting)
I have been giving much thought to writing yet another filesystem, which would fill the needs of home/archival/media box users. Essentially it would be like ZFS, except it would improve upon ZFS's dynamic striping. I would have dynamic parity, such that the number of disks in the stripe-set and number of recovery blocks is completely independent per-file, ala PAR2. ZFS is still just as bone-headed as older filesystem because the vdev's are still atomic, you make a raidz, and it stays that way. The integrity would be on a per-file basis only. So you could add and remove disks at will, no dangerous re-striping operations, and protection and recovery from on-disk corruption. If you lose too many disks, you only lose the information on those disks. A file need not be striped on every disk. Only when a particular file has less parity blocks than missing blocks, wherever such blocks may be, is the file gone. Files on disk should always be recoverable, regardless of "corrupt superblocks", or something similar. This could probably be done using FUSE and some quick and dirty code.
Why?
1. We want a lot of storage
2. We want it expandable, no dangerous restriping or filesystem expansion. There can be NO BACKUPS!
3. We don't want to wake up in the middle of the night and wonder if the next fsck is the last.
4. We only care about enough performance to run the media center, i.e. record TV and play movies.
Performance requirements (Score:5, Insightful)
The advantages of RAID 0 versus RAID 1 versus RAID 5 have already been covered in detail, here, and in many books and websites.
However, allow me to address the issue of how they relate to a media center:
Firstly, when you say "media center/media server", do you mean "I just want to build myself a kickass Tivo?", or do you mean "I want to serve video for everyone in my frat house, simultaneously?"
If the former, consider that Tivos ship with 5500 RPM drives for several reasons:
1) They're cheaper than faster drives
2) They run cooler than faster drives
3) They run quieter than faster drives
4) They use less power than faster drives
5) They're more than fast enough for streaming a single video to your TV while recording another
Long story short, if you're just building a "free" Tivo with a kickass drive array, performance is *not* an issue. Keep in mind that if you're building a set-top box of sorts, the low heat and low noise features are *very* big benefits. You probably want RAID 5, and/or JBOD.
If, however, you're planning on serving video to more than a handful of stations simultaneously, you may need to consider performance. This is a vote for RAID 0 and/or RAID 10.
Now, the second axis: How important to you is this data? Really?
I've got over 300 gigs of drive space on my Tivo. Most of it is the last two weeks of television reruns (Scrubs, 6 copies of last Thursday's Daily Show, etc.), movies I recorded but won't watch, etc. There are about 10 gigs (3%) of video on there that's been saved for a few months, and frankly, I couldn't tell you a single thing on there that I'd miss if my drives went belly up tomorrow. So: do you *really* need to save all those Seinfeld reruns on a highly-redundant storage array? How *much* of the stuff on the server do you really need to keep?
Assuming it's less than 50% (in the Tivo scenario, it probably is), consider using JBOD for most of your storage, and maintaining a single backup drive, or small backup drive array. Or just backing up the good stuff to DVD.
In summary: If you're just building a Tivo, you probably don't really need the performance, or redundancy that RAID offers.
Infrant X-RAID is the solution (Score:5, Interesting)
Buy an Infrant RAID with the two biggest drives you can afford. Let's say two 750GB drives or whatever's on sale that week. It starts out acting as RAID-1 with the drives mirroring. So you have 750GB of "safe" storage. Now you add another 750GB drive. Okay, now you have 1500GB of storage with one of the drives acting as parity drive (RAID-5). Add a fourth drive and how you have 2250GB of "safe" storage. Now you come back and just replace one of the original 750GB drives witha 1TB drive. Do you get extra capacity? No...not initially. But the drive is fully formatted and integrated as X-RAID. What this means is that eventually after you have piecemeal or onesie-twosie upgraded all four drives, suddenly the X-RAID resizes itself to match the capacity of the new drives with no transfer or downtime. So in theory if you wanted to upgrade your RAID, buy four 1TB drives, swap them out one at a time (letting each one rebuilt the array) and then at the end you'll have 3TB RAID isntead of the old 2250GB RAID and all the data intact.
http://www.infrant.com/products/products_details.
I have three ReadyNAS units and love them to death. They are a little fussy about drive temperatures (I guess that's a good things but, I may get like 40 emails during the course of the day about it and it's not like I'll drive home from work to turn up the A/C in my house). My only sadness is that Infrant doesn't have a higher capacity unit than four drives (oh please oh please, eight drives with a RAID-6 type protective hotspare in one nice rack-mountable unit would be my ultimate dream).
-JoeShmoe
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unRAID (Score:3, Informative)
I can't believe no one has suggested an unRAID [lime-technology.com] server. You get redundancy, storage that can grow by just adding another drive, low power consumption, affordability, and the ability to telnet in. (Plus it runs Linux!) I really like this solution since the data isn't spread out over a bunch of disks in a way that only the RAID controller can understand. Instead it's just a bunch of files on a bunch of disks, with an extra parity drive for reliability.
If a drive goes down, you can just pop a new one in and recover the lost data from the parity drive. If two drives simultaneously fail (unlikely), you lose the data on the drives that failed. Compare that to the nightmare if your RAID controller fails.
Here's my unRAID server [coppit.org], built for $400 plus the drives. I love being able to do backups by just running rsync. Once the author gets sshd built into the system, I can even do automatic incremental snapshot backups using rsync --link-dest.
AMEN! (Score:3, Informative)
I 100% agree with you on unRAID - it rox! I'm not using any sort of background Linux stuff to do my backups but I do use an unattended backup package that works just fine with unRAID (Acronis). The speed could be better (I'm not yet on the 2.6 based version) but it keeps up stutter free with my XBMC box so it's fast enough for me.
Simple: unRAID and use your JBOD (Score:3, Informative)
Some limitations: Parity drive must be as big or bigger than all others. Each drive is a seperate mount point unless you use a funky sort of shared folder feature. The system doesn't have as high a transfer speed as a RAID would, however it streams video for me to an XBMC XBOX1 just fine. It doesn't have a super robust system to notify you of failed drives out of the box although some users have added this functionality. Not a whole lot of security although I've met someone who has added this on and the developer is also working on expanding this in the future. Pretty decent support overall IMO and he's just moved to the 2.6 kernel - I've yet to upgrade though.
All in all this system seems to be perfect for HTPCs and I also use it to store backup images of all my workstations. All of my music and DVDs are stored on it and I'm about to build a second one as I need still more storage and have "spare" drives that I've pulled from the existing one as I've upgraded that I'd like to put to good use
Software RAID5 or Manual Redundancy (Score:3, Informative)
First, forget hardware RAID solutions. While their effectiveness is debatable for commercial and enterprise applications, it's definitely overkill for a home solution (particularly a media server). (Unless of course you have more money than sense.) But Linux RAID (md, multi-disk) is mature, stable, and well-tested. It's portable from one machine to another. It's free. With even modest hardware, it will be plenty fast for a home media server. Don't even bother with those pseudo RAID solutions that are built into your motherboard (or implemented via firmware or a proprietary driver): Linux software RAID and true hardware RAID beat these solutions in just about every conceivable way.
Now, do you really need RAID? Many people equate RAID and backup. They are not equal. RAID is no substitute for a good backup. In the case of a media library, you do own all the media, right? :) There's your backup. Worst case, you lose the time spent ripping the media. So there's an argument to just use JBOD. However, I do use RAID5 for a bit of safety. If two drives fail simultaneously, I fall back on the media. But if only one drive fails, then I can replace the drive, rebuild the array, and lose very little time. It's quasi-backup. It's just too expensive for an individual to maintain multiple live copies of this much data.
If I were to build a fileserver for someone right now, this is what I'd use:
I have another post on this thread where I went into more detail about the choice of case. Quick summary: if you care about noise, don't cram your drives close together, or you'll have to use an obscenely loud high-speed fan to keep them cool. If you allow at least 0.5" between each drive, you can keep your drives cool with a low-speed (quiet) fan. That's why I'm buying the Lian Li case mentioned above: room for up to nine drives, with adequate spacing between each.
Forget RAID (Score:3, Insightful)
I find the best is to have another computer or possibly external drives sitting somewhere, and just make weekly/daily/monthly/whatever rsync copies between them. This allows for you to recover from user error like accidental deletions, and if the entire system goes down your covered. Want more space? add a drive and presto, more space. No special configuration required. No expensive controller cards (or cheap and slow controller cards) required.
And if your like me, you have another set of drives stored offsite... but I'm pretty paranoid about such things. =P
Re:RAID (Score:4, Funny)
Actually, the failed hard disk will personnaly walk to you.
mdadm (Score:3, Informative)
If it is a Linux server, you're already using mdadm, which has a monitoring daemon with e-mail notification.
Re: (Score:3, Informative)
root @ backup (/usr/src/linux) cat
Personalities : [linear] [raid0] [raid1] [raid10] [raid6] [raid5] [raid4] [multipath]
md0 : active raid5 hdj1[3] hdi1[4] hdg1[2] hdf1[1] hde1[0]
468880896 blocks level 5, 4k chunk, algorithm 2 [5/5] [UUUUU]
unused devices: <none>
[U] is Up. [_] is Down.
LVM is your friend (Score:3, Informative)
Not at all, these days one does have better options than rebuilding a blank array. Read up on LVM, it is powerful stuff.
Replace the drives in the array one at a time, allowing time for the array to rebuild. Then you can grow the volume to make use of the extra capacity. Yes it will require some planning and will probably take a week to slowly merge in the new set of drives, but it sure beats a bare metal restore b
Re: (Score:2, Informative)
Re: (Score:3, Interesting)
Yep. And if you boot something like Knoppix you can keep the OS on cdrom and storage on the raid device. Samba config goes on a usb key. I have two servers in a corporate environment running software raid 5 and booting knoppix. Updates are nearly impossible, but you can keep the updates on the usb key (tzdata) and untar right over the top of UNIONFS after boot. Either that or just download a fresh Knoppix version (I've gone through 3 versions now). The software raid in Linux i
Re:go for RAID-5 (Score:4, Informative)
I concur. You would be crazy not to have redundancy--without out it one disk failure will pull down a good chunk of your data.
As for growing the array. From what I understand (and I have not tested this) you can grow the size of the array if you replace all the disks (one at a time with a resync obviously). Also, as of linux 2.6.17, you can add a disk to the RAID and grow it that way.
I would caution against making your array very large (either in disks or in space). Consider the case of a 3 disk RAID array where each disk has a probability of failing in any given second of 10^-10 (you would do this analysis using the reconstruction time of your array as the time window). The probability for any two drives not failing is (1-10^-10)^2. The total number of 2 drive pairs in a 3 disk RAID is 3, thus the probability of the array not failing in any given second is (1-10^-10)^6=0.99999999940. Over a period of five years, the overall probability of no two drives failing is (1-10^-10)^(6*157680000)=0.909729. If you increase the array size to 10 disks, the overall probability of two drives failing is 0.241927 (the number of 2 drive combinations is 45 so you replace the 3 with 45).
Re: (Score:3, Informative)
Why? Linux software RAID (md) does a fine job with excellent performance, assuming you are not saturating the PCI bus (solution: use PCI Express or PCI-X instead). With sufficent bus bandwidth, software RAID outperforms the majority of soft RAID (rocketraid) and hardware RAID controllers.
You can do this with md wi
Re: (Score:3, Informative)
The 4-3 devices modules are cute, but a pain to deal with when you want to replace a drive (you have to rip apart 4 sets of cables). I'm not entirely satisfied with the 4-3 modules that I have, I prefer the older 3:2 units with a 80mm fan. Stick to only putting 2 drives in those old 3:2 units and you get superior airflow because there's no strange grillwork between the intake fan and the hard drives. You might
Re: (Score:3, Interesting)
I was skeptical of the 5:3 backplanes too. But the 5:3 backplanes actually do a pretty good job of cooling.