Revisiting the Five-Minute Rule 153
In 1987, a study published by Jim Gray and Gianfranco Putzolu evaluated the trade-offs between holding data in memory and storing it on a disk. Known widely as the "five-minute rule," their research was updated and expanded 10 years later. Now, as jamie points out, Communications of the ACM is running an article by Goetz Graefe with another decennial update, evaluating the rule using hardware and software typical of 2007, with an eye toward how flash memory will affect the situation. An excerpt from Graefe's conclusion:
"The 20-year-old five-minute rule for RAM and disks still holds, but for ever-larger disk pages. Moreover, it should be augmented by two new five-minute rules: one for small pages moving between RAM and flash memory and one for large pages moving between flash memory and traditional disks. For small pages moving between RAM and disk, Gray and Putzolu were amazingly accurate in predicting a five-hour break-even point two decades into the future. Research into flash memory and its place in system architectures is urgent and important. Within a few years, flash memory will be used to fill the gap between traditional RAM and traditional disk drives in many operating systems, file systems, and database systems."
for those wondering: (Score:5, Informative)
"The 5-minute random rule: cache randomly accessed disk pages that are re-used every 5 minutes."
Not to be confused with (Score:5, Funny)
Re: Not to be confused with (Score:2)
Nor the funkier 3 minute rule [youtube.com].
Re:Not to be confused with (Score:4, Interesting)
The more useful 5 second rule [wikipedia.org].
That's just utterly disgusting. Do people in the US really believe that you can eat food that's fallen on the floor if you pick it up fast enough?
Re:Not to be confused with (Score:4, Insightful)
Re:Not to be confused with (Score:5, Funny)
I'd rather be a disgusting American than a naive European with no sense of humor..
Re:Not to be confused with (Score:4, Insightful)
As a not so naive Brit, we have our much superior 3 second rule for the same thing.
I'd like to know what the GP has on the floors in his house that is so toxic that the tiny amount that will rub off on food is detrimental for your health? How on earth do people survive in places without nice sealed floors and cleaning chemicals? You'd think we'd have evolved some method of protecting our bodies against stuff like that.
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Are those Imperial or metric seconds?
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No silly, but if you catch it on the bounce, it's like it never happened
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Do people in the US really believe that you can eat food that's fallen on the floor if you pick it up fast enough?
Well, if you accept that my brother fits the definition of "person", and various snacks (pretzels, chips, hard candy (still wrapped)) as "food", then some people in the US don't restrict themselves to 5 seco^Wminu^W^da^Wmonths.
Though I am sure the attitude is not limited to the US.
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You need to watch the Mythbusters episode on the 5 second rule.
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Well the confusion is, unlike your dirt-floor huts full of your own feces, in real countries like America we have clean tile floors with miraculous inventions we call "mops".
Carpets are safer ... (Score:4, Interesting)
Since this is slashdot, I'd bet most will pick bacteria over carpet fuzz any day ... after all, if it doesn't look fuzzy ...
or this ... [scienceline.org]
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Weren't there studies done that show most bathrooms (maybe not public ones...) had less bacteria than most desks in people's offices?
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Normal floors are probably safer than your hands. If it's in your own home and you just dropped it or something, I can't even really imagine why it would be mentally bothersome.
It's not really an issue if you have a dog, though.
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> that's fallen on the floor if you pick it up fast enough?
Short answer: no, but yes.
Long answer: There are two kinds of people. Some people won't eat food that has fallen off the plate onto the table, their lap, the chair, the floor, wherever. If it fell, it's "dirty", and they throw it away.
There are also people who think this is silly. If there's no visible dirt on it, or if you can brush it off, hey, it's still food. Unless it fell in
Combined rule (Score:2)
The lesser known 5 minutes 5 second rule combines the two: It states that if the case is left off a desktop computer for more than 5 minutes and 5 seconds Pizza and coke will spontaneously migrate from a computer lab desk and contaminate your RAM, CPU and motherboard.
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Will the 5 minute rule increase to 10 or even 20 when RAM becomes mega-cheap, and 64 bit OSs take off to take advantage of >4GB memory addressing?
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Flash memory? (Score:2, Insightful)
I couldn't quite figure out if the article willfully ignored the advent of SSDs or was written before they were available and not updated to include them (but it appears the article was updated to include other current technology).
Given the fact that SSDs are likely going to replace rotational media for most applications in the future, it makes this article basically meaningless, at least insofar as the fact that flash memory and the disk are/will be synonymous. As the article is basically predicated aroun
What article? (Score:3, Insightful)
The article I read spent a good deal of time talking about flash memory. What article are YOU referring to?
Re:What article? (Score:5, Insightful)
The article I read spent a good deal of time talking about flash memory. What article are YOU referring to?
The article treats flash as something you place in between hard drives and memory. This turned out not to happen (with a few exceptions). SSD's simply replace hard drives. Hybrid systems are rare, and it doesn't look like they will become more common -- either you can live with the slowness of hard drives, or you can't. The mainstream will switch to SSD's for everything except backup applications.
There are some hybrid SAN's, but they're damn expensive. At that price they have a hard time competing with simpler pure-flash SAN's.
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The grandparent was talking about hybrids, but also something new. If and when MRAM becomes possible the technological hard drive wether spinning or flash is gone.
Indeed I am waiting for a true hybrid system to be built. One that has the OS installed in read only flash and applications on a separate drive. you might ask why? but then stop to realize what would happen if viruses couldn't overwrite the system settings. that to clean up a virus all you had to do was to reboot.
OS patches? (Score:2)
I am waiting for a true hybrid system to be built. One that has the OS installed in read only flash and applications on a separate drive. you might ask why? but then stop to realize what would happen if viruses couldn't overwrite the system settings. that to clean up a virus all you had to do was to reboot.
How would such a hybrid system correct a discovered defect in the operating system?
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I propose a physical switch to toggle between read/write and read only. Even if it could be controlled remotely by a management server, it would provide a nice increase in security.
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I propose a physical switch to toggle between read/write and read only.
And have social engineers disguise malware as OS updates or dancing bunnies [msdn.com], prompting the home user who doesn't understand risks to flip the switch to see the dancing bunnies.
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And have social engineers disguise malware as OS updates or dancing bunnies, prompting the home user who doesn't understand risks to flip the switch to see the dancing bunnies.
You can't make something 100% foolproof, the world will just invent a better fool. But you can make the lives of the non-fools better.
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propose a physical switch to toggle between read/write and read only.
And have social engineers disguise malware as OS updates or dancing bunnies [msdn.com], prompting the home user who doesn't understand risks to flip the switch to see the dancing bunnies.
If I'm the admin of that system, I'd install a key switch and keep the key for myself.
Better yet, I would install a keypad that is synchronized to my RSA keyfob - that way I could give the user a one-time code over the phone if I needed the button pushe
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If I'm the admin of that system, I'd install a key switch and keep the key for myself.
That might work for you, but it won't work for everyone. Should the
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Should the owner of a home PC be the PC's admin by default?
Not my father or sister. It would save me lots of headaches and desperate phone calls if I had that switch.
In fact, it might be worthwhile to offer this as a feature - software publishers could form a guild to guarantee software authenticity. Have an optional phone number you can call w/ the serial # of your keyswitch and the code of the sfw you're installing. They'd give you a code for the switch that only opened the areas of the disk and/or regi
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In fact, it might be worthwhile to offer this as a feature - software publishers could form a guild to guarantee software authenticity.
How would developers of free software [gnu.org] gain access to a publisher in the guild? And who can afford to make multiple international long-distance telephone calls, one to each publisher's headquarters?
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MSDN? Noted. The author of that article has a vested interest in an operating system prone to such exploits.
Ad hominem.
the Linux user is somewhat less likely to a: have admin rights or to b: grant admin rights to a program if he has them.
In the case of Linux on the home desktop, the owner of the PC has admin rights, and I don't see how granting setuid is any harder to social-engineer out of an inexperienced Linux user than out of an inexperienced Windows user.
When I look at bunnies, I see food.
What about dancing scantily clad people of the appropriate sex?
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Errr - realize that a number of people migrate to Linux because they believe Linux to be more secure than Windows. Such people are more likely to do some studying, and follow best practices as they learn them. I'll even go so far as to say that people migrating to Linux tend to be more security minded when they need or want to use a Windows machine.
In the end, I'll trust an inexperienced Linux user just a little bit further than I'll trust that "average" Windows user. At least our inexperienced Linux use
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Errr - realize that a number of people migrate to Linux because they believe Linux to be more secure than Windows. Such people are more likely to do some studying, and follow best practices as they learn them. I'll even go so far as to say that people migrating to Linux tend to be more security minded when they need or want to use a Windows machine.
The same knowledge and practices protect you equally well in Windows. Why, then, go through the additional pain of migration when you've already solved the pr
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Among other reasons - I don't have to pay Linux a couple hundred dollars for a license every time I set up a new machine. No validation checks, no asking special permissions codes to unlock a machine because I've reinstalled to many times, or the hardware has changed to a greater degree than allowed.
I believe that in the current economic climate, more and more people will be leaving microsoft behind.
I've had some success proseletyzing at work. I work with a number of Mexican and South American immigrants
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All of them love the idea of running a legal operating system, for FREE.
Pretty much everyone gets Windows for "FREE". It comes with their computer. Which is why the economic argument for switching makes as little sense in the home market as it does in the corporate market.
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Everyone gets windows for "free". Sorry, that is wrong on two levels.
First, I mentioned that many of my coworkers are immigrants, and that some of those are almost certainly illegal. These people don't make a lot of money, nor do they have easy routes to establishing credit. A number of these people buy (or steal) or accept ancient machines, and broken machines, as donations or hand me downs.
It is positively amazing, the array of hardware that they have to work with. Given time and motivation, I could b
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Everyone gets windows for "free". Sorry, that is wrong on two levels.
Pretty much everyone. Although since your whole line of reasoning here is a big straw man, I suppose piling another one on top isn't that unsurprising.
Some don't. But, more switch this year, than switched 5 years ago.
Given how much Linux has improved in even just half that time, it's hardly surprising more people find it usable.
There are many of us who are willing to purchase their machine in bits and pieces, exercising our right
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The author of that article has a vested interest in an operating system prone to such exploits.
No OS is "prone to such exploits". It's a user issue.
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Presumably by the tech flipping a hardware rw/ro switch on the drive after proper isolation conditions are met.
Yes it's a pain, but much like dentistry it's a preventative pain that spreads a small controlled annoyance over a planned schedule as opposed to a big problem cropping up all at once unexpectedly (and usually at the worst possible time).
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Presumably by the tech flipping a hardware rw/ro switch on the drive after proper isolation conditions are met.
If such a system were deployed in home PCs, how much would it cost for the tech to visit each user and flip the switch? I see no way to make such on-site service cost-effective.
I already have this. (Score:2)
Indeed I am waiting for a true hybrid system to be built. One that has the OS installed in read only flash and applications on a separate drive. you might ask why? but then stop to realize what would happen if viruses couldn't overwrite the system settings. that to clean up a virus all you had to do was to reboot.
You mean like the way I run Windows under VMware and roll back to a snapshot?
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One that has the OS installed in read only flash and applications on a separate drive. you might ask why? but then stop to realize what would happen if viruses couldn't overwrite the system settings. that to clean up a virus all you had to do was to reboot.
Why would rebooting clean up a virus that had inserted itself into the user's data and programs ?
Or are you proposing a system when the user can't write to anything as well ? We have those already, they're called consoles.
ZFS (Score:2, Interesting)
The article I read spent a good deal of time talking about flash memory. What article are YOU referring to?
The article treats flash as something you place in between hard drives and memory. This turned out not to happen (with a few exceptions). SSD's simply replace hard drives. Hybrid systems are rare, and it doesn't look like they will become more common -- either you can live with the slowness of hard drives, or you can't. The mainstream will switch to SSD's for everything except backup applications.
There are some hybrid SAN's, but they're damn expensive. At that price they have a hard time competing with simpler pure-flash SAN's.
Except if you're using ZFS. You can put a (SLC or MLC) SSD drive into just about any system and tell it to act as a (write or read) cache.
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tOM
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There are some hybrid SAN's, but they're damn expensive. At that price they have a hard time competing with simpler pure-flash SAN's.
FWIW, Sun's ZFS has the ability to automagically use flash drives as intermediate stage in front of rotating disks.
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The other problem with the role ascribed to flash memory in the article is the write-wearing of flash. If flash memory decays with fewer writes than disk memory, there's a trade-off between the overall lifetime of the disk subsystem and the use of flash memory for caching/buffering. If you do most of your active writes to flash as a buffer before doing sector-based writes to magnetic disk, sure your performance is better, but you shorten the lifetime of the disk subsystem.
A more likely scenario is to have a
Re:What article? (Score:5, Informative)
Hybrid systems are rare, and it doesn't look like they will become more common.
You're probably right when we talk about desktop PCs and laptops. I'm sure the latter will be SSD only in 5-10 years time, and desktops are also losing terrain quickly against laptops.
But when we look at datacenter grade enterprise storage, hybrid systems are currently picking up fast. The advantage is that because of the fast 'flash memory cache' you can use SATA disks instead of the FC/SCSI drives, where the former are both much bigger and much cheaper. Instead of 300 146GB 15K FC disks, you only need 30 1.5 TB 7200 RPM SATA disks. For the same capacity this results in much lower power bills, less DC floor-space costs and much better performance.
If you say "There are some hybrid SAN's, but they're damn expensive.", have a look at what [shameless plug-on] Sun is doing [sun.com], and yes, I work for Sun [plug-off]. But other storage vendors (NetApps, EMC, IBM, etc.) are starting to do similar things.
So the whole "storage-stack" gets more and more hybrid and integrated. It consists of the full gamut of DRAM, flash memory, hard drives and finally tape. Each of these have their own strength and are used best in combination.
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But other storage vendors (NetApps, EMC, IBM, etc.) are starting to do similar things.
Actually, EMC seem to be most emphatically NOT doing it and are just classifying flash as another tier to be managed by the storage admin,
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No Common Hybrids? What about ReadyBoost and ZFS? (Score:2)
Also I rememeber that one of the main disadvantages of Btrfs over ZFS was that I doesn't support using SSD to speed up overall access, while ZFS does [sun.com].
Readyboost is just to get over low memory limits (Score:2)
But SSD is cheaper than ram? (Score:2)
I am not too sure how the cost/benefit of ReadyBoost stacks up, but I'd guess that plugging in a decent flash-drive would be cheaper than trying to find obsolete Laptop ram.
The wikipedia entry for Superfetch [wikipedia.org] doesn't mention anything about only being 32bit, and it sound like it w
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Readyboost and Superfetch are really just hacks to get around the 3GB or so ceiling in 32 bit Vista due to incomplete support of the Pentium Pro and later processors (PAE extension). With the 64 bit versions (or the server 32 bit versions, or any OS produced by anyone other than Microsoft in the last decade) you can use real memory instead for improved performance. Consider that you are grabbing all that stuff from disk and doing the relatively slow write to flash to save time when it needs to go into memo
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There are some hybrid SAN's, but they're damn expensive. At that price they have a hard time competing with simpler pure-flash SAN's.
Er, what ? NetApp and Sun are two examples of vendors with "hybrid" NAS/SANs that use SSDs as an extra caching level, and they're _very_ price competitive with pure-flash SANs. Particularly if data volume is important.
Or are you calling a Linux machine stuffed with Intel X25-Es and an iSCSI target a "SAN" ?
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What's the problem? If you need to store 1TB and you can live with the slowness of hard drives, you use hard drives. If you can't, you use SSD's -- or possibly an array of small fast hard drives, but SSD's will most often be cheaper.
What you don't do is build a hybrid system with automatic page migration between SSD and hard drives -- and that is what the article assumes will be commonly used. Hierarchial storage has a very small niche, and SSD's won't make it more popular.
Hence the article is useless.
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Inexpensive SSDs tend to be pretty slow, defeating the point of going SSD.
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Intel SSD's are inexpensive per IOPS, compared to just about anything else. They aren't even particularly expensive per GB compared to 15K SAS drives.
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Wait a year and a half, it'll be here.
How is that even Slashdotters seem to forget nothing in computing is static, that any arbitrary amount of storage or memory or speed will inevitably come to exist? It was only a few years ago that 1tb HDDs were an object of speculation themselves, SSDs will get there soon enough.
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In any case, they need to hurry the hell up. Papa needs a new pair of dimms...
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Wait a year and a half, it'll be here.
Yeh, but by then you'll be able to get 2TB hard drives for 1/10th the price.
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Wow...almost nothing but offtopic and redundant posts so far.
Well, this is /. What do you expect?
Natalie Portman and hot grits.
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I'm somewhat curious as to why people would moderate the original post off topic? It's specifically addresses the article and is ABOUT the article. How is it off topic?
Given the fact that every other post in the article is modded offtopic, I suspect someone has gone through and just modded everything off topic.
Either way, the point still stands. The article fails to recognize or address SSDs in any way, shape or form. As such, the article is basically mostly irrelevant in 2009 and going forward. It's i
Re:Flash memory? (Score:4, Informative)
I couldn't quite figure out if the article willfully ignored the advent of SSDs or was written before they were available... As for the post by Argent, I wasn't sure if that was addressed to me or not - if so, I have no idea what you're talking about. Your post has absolutely nothing to do to with my original response.
Argent's post refers to "flash memory". You said the article ignored SSD's, however it did not. "Flash memory" is the technology that SSD's are composed of. Did you not know this? "Flash memory" is all over the article.
Flash SSD's will not replace SATA drives anytime within the next 4-6 years. In technology time, that's such long period of time, it would be quite difficult to make a credible projection for the consumer market space. For servers, where the segment is dominated by 10K/15K drives, you can expect flip over within 18 months.
C//
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I for one do not need a 350 GB HDD on my notebook such as I have now. I would love to have better power life and snappier response though. 80GB is comfy for me, and has been so for 5 years. Movies and stuff I put on an external drive, and transfer when I need it. Netbooks already d
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Depends what segment you're talking about. There isn't one market for HDD's, there are many. In both the enterprise archival and consumer mass storage segments, drives are sold pretty much $/TB. In that segment, you won't see significant penetration for 4-6 years. In other segments, sooner. I agree with you: I want a flash SSD for my laptop currently; it just hasn't quite yet reached the right price point. It will soon. And you're right: it's not $/GB that will be the deciding factor there.
There's also no r
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If you've still got an external(or internal) physical HDD, then SSD's have not taken over. They've become a part of a new solution, not replaced an old solution.
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No shit, that is exactly my point.
SSDs are set to replace rotational media. That was what I stated.
So... to make it more clear to the people with reading comprehension issues:
Flash memory is set to replace rotational media.
This article indicates that Flash Memory (AKA SSDs) are only going to be an intermediary between rotational media and RAM. This is clearly not going to be the case going forward... this is WHY I wrote the GP post and pointed out that it's invalid.
WTF. Seriously. Are people that incapa
External hard drives == memory hierarchy (Score:3, Insightful)
This article indicates that Flash Memory (AKA SSDs) are only going to be an intermediary between rotational media and RAM.
If your handheld device or subnotebook PC has only an internal SSD and no internal hard drive, then you will store any data that doesn't fit on your SSD on a hard drive plugged into a Hi-Speed USB port, copying it to the SSD when it is needed. For example, you'd keep the video footage that you are editing on the SSD and other projects on the hard drive. That sounds to me like a memory hierarchy, albeit one that occasionally requires manual intervention to connect the (offline) long-term mass storage to the
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the king is dead (Score:3, Interesting)
What I love about slashdot is its scalability. The discussion ranges anywhere from the design of a Google data center in 2015 to some guy's psychological stance toward his next netbook purchase in 2009. Sometimes it's unclear which end of the spectrum is under debate, but the discussion happily progresses in a state of astral superposition. When this gets too confusing, even for slashdot, the moderation system helps to sort things out. For example, if the comment
Flash memory is set to replace rotational media.
is moderated +1 insightful, then we know
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There are millions of people already using SSD's as (superior) drive replacements.
Do you really want evidence of the fact that SSD's are already replacing drives, that many millions of them have been sold specifically for that purpose, that even companies like Apple offer SSD's as alternatives solutions to rotational media in their standard packages?
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You ask for evidence. How about some evidence that SSD's are being used anywhere in the way that you describe.. as a cache between rotational media and ram.
* Most Sun 7000-series storage systems. Probably numerous tsandalone ZFS-based systems as well.
* In the fairly near future, NetApp storage systems (and probably other vendors over the next year).
* Any Vista system using ReadyBoost.
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ReadyBoost is actualy made moot by SSD's, which perform better than ReadyBoost (without the extra layer of complexity.)
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Sun 7000 doesnt use SSD's.. but it does use several types of FLASH memory.
This is called "being a pedantic ass". Especially since Sun themselves use the terms interchangeably.
ReadyBoost is actualy made moot by SSD's, which perform better than ReadyBoost (without the extra layer of complexity.)
No, it is not. Unless SSDs have suddenly dropped to the same price as thumb drives, or increased in size to the same as magnetic media.
I really must admit I'm struggling to understand why anyone would try and a
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Flash is an SSD, but not every SSD is flash...
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The reason not all flash is an ssd, because in some cases, it's just a chunk rectangular storage. The BIOS isn't necessarily in a file system, nor does it typically have a special drive-like controller or unusual interface circuitry, it's a bare flash chip. Lots of microcontrollers have flash but don't have anything like a drive controller in them, it's just a different type of memory.
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I'm not sure that is entirely true. High capacity SSDs will need to write large chunks to have good write speeds, and to reduce wear. Having a separate small chunk cache will still be necessary.
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SSDs are not likely to replace traditional hard drives any time soon, if ever. The cost differential is simply too high. While it is true that SSDs can effectively replace HDs on systems which do not require large amounts of storage (say, 64G-256G), the fact of the matter is that a 256G SSD is still three times as expensive as a 2TB hard drive. That is a 24:1 cost factor.
At the same time SSDs are becoming capable of replacing systems which do not have large storage requirements, HDs are becoming far more
I thought you were referring to the 5 second rule (Score:4, Funny)
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Not as long as you scrape all the dog hair off first.
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It's just a bit dirty, it's still good, it's still good!
Re:I thought you were referring to the 5 second ru (Score:2)
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Stickier food may be better to eat off of the floor, as the part that touched the floor is somewhat more likely to stick to the floor, rather than some of the floor sticking to the food that you eat.
Its an interesting subject that probably needs more investigation.
Sticky foods often leave a layer on the floor and as a result the part you pick up has only been in contact with the floor. However, around the edges of the contact the sticky food is very good at picking up loose dust and the like.
Runny liquid-covered foods may stay on the floor at the slightest contact, avoiding the sticky problem, but what about dirt that gets mixed into the top layer of the dropped food during the impact?
Hard dry foods
Do the old premises still apply? (Score:2)
These days, the database is not what it used to be. Local clients use shared memory. JVMs and entire web servers are incorporated directly into the database executables. The old concept of the separation of the database from its clients no longer applies.
When you are running a database, what business does the OS have, deciding what data is to be paged in or not? The database is in a far better position to make these decisions, and it can be based on much better rules than "5-minute" heuristics.
Extending the memory cache abstraction to paging (Score:2)
The way I see it, the advent of SSD storage gives us the ability to extend the cache layering abstraction we already use into a smooth continuum between the cpu's L1 cache (L2, L3, dram simms, etc...) and traditional HD-based disk cache. SDD doesn't quite close the gap but it actually fills a major portion of it.
The article makes the mistake of assuming fairly small SSDs, but is otherwise spot-on. It isn't possible to use tiny SSDs in the 8G range as a paging medium for caching memory, it simply isn't eno
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I'm not sure where people get this acceptable wear levels for SSD's thing.
All the math I've seen indicates that, presuming reasonable wear algorithms, if you write the volume of your data to disk every day your drive will last for about 30 years and that it will scale linearly with shifts up or down in that amount. An ordinary hard disk lasts about 5 years, so for your 8 GB disk you'd have to be writing approximately 48 GB of data to it every single day in order for it to not last longer than a current HD,
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I don't quite see how it would allow you to more fully utilize resources. This is usually the argument given by people that think paging somehow will increase your systems performance because it makes more optimal use of all the memory.
Unfortunately, this is only true if you have the perfect paging algorithm. It basically requires that you have a paging algorithm that is almost psychic in its ability to predict what future data may or may not be needed. Current paging algorithms, although no doubt comple
Universal memory (Score:2)
Advanced "universal" memory technologies (fast, non-volitile) such as MRAM, FRAM, maybe RRAM will alter this landscape significantly. While some are available now, we'll have to wait a few more technology generations before they have the density to realistically compete with hard drives or even Flash.
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So I RTFA to see if it answered any of my questions and it seems that they are just saying that they don't have the answers either. I don't know if I agree with their use of flash as extended ram. Why not just make it a super fast drive that sits close to the cpu and give it the illusion of being an IDE drive so us normal users can just make it a swap partition. Oh, and give the chip a socket so we can upgrade/replace it later. I don't think it would cost manufacturers a great deal more to add one more sock
Erase traffic burns up SSDs (Score:2)
I don't know if I agree with their use of flash as extended ram. Why not just make it a super fast drive that sits close to the cpu and give it the illusion of being an IDE drive so us normal users can just make it a swap partition.
A swap partition has a lot more erase traffic than a data partition, and access patterns high in erases are thought to wear out SSDs faster than hard drives.
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Does swap really erase? I was always just under the impression that if a block was no longer used it was just demapped. If the OS decides to write to that block again it just merely overwrites that block. Unless I'm missing something here? I thought the problem with running swap on a flash was the sheer number of writes involved, not the erases. The problem with erasing, from what I can tell, is when you have a temp folder that keeps erasing and further reducing the number of free whole blocks by fragmentin
rarely-rewritten logical sectors (Score:2)
Does swap really erase? I was always just under the impression that if a block was no longer used it was just demapped. If the OS decides to write to that block again it just merely overwrites that block.
A flash block must be erased before it is overwritten, and each sector is guaranteed for only about 100,000 erases. Lots of writes are fine on larger SSDs because the wear leveling program in the drive's controller will move rarely-rewritten logical sectors (such as free space and read-only files) to more-worn physical sectors. But if you're devoting an entire device to swap, there won't be a lot of rarely-rewritten logical sectors for the controller to make use of.
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But if you're devoting an entire device to swap, there won't be a lot of rarely-rewritten logical sectors for the controller to make use of.
Only if you have a very unusual swap load, where the swap space is 100% full and every swap operation is exactly that; an exchange of some pages between memory and disk. In practice, a swap partition is likely to be largely full of data that isn't ever accessed. For example, if an app leaks some memory, this will be swapped out after not being used for a while and never swapped back in. If an application spends most of its time idle, it will be swapped out and stay on disk for a long time, being occasion
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Obviously, the problem with running Puppy in a ramdisk and not having it write back until shutdown is that if it crashes you'll lose your data. You can maybe do a full install to avoid that, I'm not sure ... it'd be nice if it could persist data to storage on request but I don't know if it can.
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It's small, wicked fast, includes Firefox.
To be pedantic, it's the Mozilla SeaMonkey suite. Puppy's a great distro though, especially for older machines.
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It's small, wicked fast, includes Firefox.
To be pedantic, it's the Mozilla SeaMonkey suite. Puppy's a great distro though, especially for older machines.
Hrmmm, OK! I imagine using a combined suite makes sense, space-wise, perhaps? I always liked using SeaMonkey, before the days of Firefox, so that's cool.
I *think* the version I actually used did have Firefox but that was a very long time ago now. When I used it I'm not sure if they had a package manager, even!
I should really burn a new Puppy CD so that I'm prepared when this computer dies ;-) Or, given the speed of the device isn't an issue if running from a ramdisk, I could buy a dirt cheap 512MB USB s