Are SSDs Really More Power Efficient? 222
Bakasama writes "Tom's Hardware compared the power performance of several available SSD cards with a Rotating HDD that was chosen specifically for its poor power efficiency.
The results seem to fly in the face of current wisdom.
'Flash-based solid state drives (SSDs) are considered to be the future of performance hard drives, and everyone seems to be jumping on the bandwagon. We are no exception, as we have been publishing many articles on flash-based SSDs during the last few months, emphasizing the performance gains and the potential power savings brought by flash memory. And there is nothing wrong with this, since SLC flash SSDs easily outperform conventional hard drives today (SLC = single level cell). However, we have discovered that the power savings aren't there: in fact, battery runtimes actually decrease if you use a flash SSD.'"
More power but only while being hammered? (Score:5, Interesting)
So if your not a laptop user and aren't currently benchmarking your drive how long will it last?
What is the power usage for real world office/ web browsing type use?
Desktop Computers / Servers (Score:2, Interesting)
Re:Not so good benchmark (Score:4, Interesting)
That's an excellent point. I was wondering if the metric should simply be different altogether.
What if we used MB/Watt or some such? The "disks" are supposed to be really good at some things (random reads) but don't hold too much advantage over others (long continuous reads). So how many WattHours does it take to load a continuous 50 GB file? How about a random 50 GB of data off a 128 GB disk? How does that compare to the same measurements with a standard magnetic disk? How does power consumption change between reading, writing, and mixed disk loads? Writing flash takes far more power than reading, doesn't it? Yet on a physical disk it's not that different in power requirements.
There are other things too. Operating systems still aren't designed around these things, they are designed for physical rotating disks. Do these things even have native controllers (designed for this purpose) yet, or are they still using modified rotating disk controllers like the first models used? As time goes on, better power saving features will show up, especially as the OS cooperates to tell this disk more information about what's going on. A well managed flash drive may be able to shut off large chunks of it's self and only wake up the bits that actually need reading/writing. That would help quite a bit, I'm sure.
PS: First time I've been to Tom's Hardware in 6 months to a year. Nice to see they found a way to make it uglier. Used to be a nice site. I especially like the "you must login to see the printer friendly version" trick.
Re:Still too new (Score:5, Interesting)
Re:Not so good benchmark (Score:2, Interesting)
if your computer has enough RAM, it will access the drive quite infrequently, especially in many cases where power drain would be of concern, such as in those UMPCs.
...which tend to have reduced memory.
I really haven't found this to be true any more. My computer hits the disk pretty much all the time (for logging if nothing else) and I've got 2GB RAM. (Currently 1100M allocated in the user space - and all I'm doing is running my fancy desktop and firefox. Linux has truly reached parity with OSX... Firefox is using 128MB with a dozen extensions) And most windows users seem to have a ton of little system tray gadgets they think they need, as well.
I do remember back when I had practically nothing running, and the disk would spin down a lot. Boy, was that annoying.
Then again, my quadro-equipped 17" widescreen laptop gets maybe an hour and a half at best. I want a smaller, more power-efficient laptop to serve as my mobile system (this one then becomes a TV and media server, I think) but haven't got around to that one yet.
Am I the only one... (Score:5, Interesting)
Who thinks that maybe the overall bettery life would be more affected by the HEAT the laptop is putting out?
After all, most laptops I've ever dealt with or owned are compact little furnaces that have their hard drives, cpu, gpu, and everything else shoved in as little space as possible in order to make room for things like batteries and keyboards.....
thus if they remove a high heat generating device (even more so with a 7200rpm drive) wouldn't logic also assume that you reduce the amount of heat needing to be removed from the system?
thus the fans would run less often, and therefore drain less battery power.
not too mention the proposed savings by simply accomplishing tasks "faster" when it comes to disk access.
Re:Swap (Score:5, Interesting)
Because in general folks know how to do it (so you're not adding code complexity in most cases) -- and it seamlessly handles the odd folks who *do* eat all of their RAM in a workload and end up needing it. (And since the folks with big working sets relatively to current states also tend to be the folks paying more money... they do get listened to -- and these are the same folks that would require a perfect patch in 24 hours when they're unhappy, so you're much better off having a little planning pre-release than trying to crowbar this in post).
The thing to do is to make the virtual memory subsystem as efficient as possible about handling swap statistics just in case you need it so that the folks who really don't need it aren't aggressively impacted.
(Note: I am a virtual memory subsystem kernel engineer -- but not on Windows. I make no claim about how efficient or inefficient Windows is at doing this as a result. I would seriously expect that since they're designing the core kernel to operate from laptops up through Windows Server Whatever --
they have to accommodate cases beyond the 4Gb in your laptop should be enough to keep everything in core, though. )
Re:Not so good benchmark (Score:3, Interesting)
Somebody correct me if I'm wrong, but isn't it true that with HDDs, the system can auto-power them down when they're idle, but with SSDs, this can't be done as easily due to the nature of SSDs?
Re:Not so good benchmark (Score:4, Interesting)
Of course if the SSD is running under load the entire time it may actually run more often than a regular HD.
from real world benchmarks SSD's only gain is from random reads. writes, sequential reads, etc all prove that SSD's are only as good as a regular spinning disk if not far worse.
It is a trade off. both have advantages and disadvantages. Maybe in 5 more years SSD's will ultimately win but for now it can go either way.
Re:Not so good benchmark (Score:4, Interesting)
Re:Still too new (Score:4, Interesting)
Call me some guy mystified by brands but after using Seagate cheap stuff (SATA) and SCSI for years and never seen these things actually fail (besides stupid filesystems), I wait for Seagate, Fujitsu, Hitachi like known brands to ship their SSD rather than being abused by some memory vendor who has no clue about the hard disks to buy some overpriced flash memory fantasy.
I also don't know the actual reliability of SSD too. What about journaling? Can it handle? A journal is still needed on SSD drive, what if kernel fails or OS filesystem layer goes nuts? A journal will be in same area of disk and will be written over and over millions of times.
I could never buy the "speed" claims of SSD not just because I use very fast SCSI stuff but I actually see the horrible performance of them in my smart phone, HD Camera. It is like performance suicide if someone dares to put a very complex applications to "memory card" instead of phones built in memory.
They are trying to ship it before it is a technology fit to general use. Much like some video sites existed while everyone had to struggle with 56K modem.
Re:Swap (Score:3, Interesting)
Used/tried a Quad G5 with 16 gig memory installed (mine has 4,5 GB).
Even on Leopard, that mainframe like monster will still create a 64MB swap file amusing us. I also saw 6 swapfiles has been created on my 4,5 GB RAM installed Tiger (OS X 10.4, doesn't have auto cleaning) after days of heavy load uptime.
Is it a strategic thing that OS kernel does? I remember reading some real weird stuff about Microsoft's tactic to swap the applications to disk even while they didn't have to but I can't find the file now. You seem to blame application developers which I can understand, does it have something to do with "pageins" and "faults" I see generally caused by badly written software?
Re:Author = Clueless and Stupid (Score:4, Interesting)
My experience matches yours. I had a huge increase in battery life when I swapped out the HD in my Fujitsu Stylistic 2300 for a CF-IDE adapter w/ a 2GB (booting Windows 2000) and 4GB (data, swap space) CF cards in it.
Ran much cooler and was absolutely silent (no fan).
I was quite bummed when the system died.
William
Re:Not so good benchmark (Score:3, Interesting)
PS: First time I've been to Tom's Hardware in 6 months to a year. Nice to see they found a way to make it uglier. Used to be a nice site. I especially like the "you must login to see the printer friendly version" trick.
I don't go there at all anymore; I've got my ipcop box running URL Filter with the Squidguard blacklist, and whatever tracking junk they run at Tom's just leaves me hanging with a 1x1 gif. It's not even worth my while to add them to the whitelist.
Re:Still too new (Score:5, Interesting)
Re:Still too new (Score:4, Interesting)
The technology already exists to reorder disk blocks based on usage and it could easily be adapted to reduce the number of flash chips which need to be activated in an SSD.
Uhhh... wouldn't that defeat the purpose of using wear leveling algorithms?
A more relevant technique would be to avoid turning on flash chips that do not have data you're accessing... but that is not as easy as it sounds when your data is (purposely) fragmented all over the place.
Re:Still too new (Score:3, Interesting)
it's different when you're just reading data, VS writing data, and these benchmarks compared power usage while writing gobs and gobs of data.
flash memory chips can use 5X as much power to 'write' data as they do to 'read' data, oh and hey if you're reading the same old data over and over, why not just have it in ram, and just not spin up a drive or read flash memory at all?
oh and wear leveling can be designed around keeping as few chips powered up as possible, you just need to reserve a bit of flash memory to cache a wear leveling pattern, so it knows when to power up and down which chips... trying it's best to keep data sets on the fewest chips, again this is a bot more complex than basic wear leveling, so it's not tro be expected on early SSDs...
Re:More power but only while being hammered? (Score:4, Interesting)
Re:Obviously that cannot be! (Score:5, Interesting)
Interesting, I didn't notice that. But one thing I did notice is that it didn't seem to take into account real world use, things such as at what point does the frequency of the extra power needed to spool up a HDD outweigh any power savings -- laptops are turned on and off a lot more than a desktop, and if the responsiveness is there, then people are going to put their computer to sleep more often to save power. None of that was taken into consideration. So technically, he may be right in some circumstances, but that might not be the way most people use them in the real world.
Re:Obviously that cannot be! (Score:1, Interesting)
It'd be nice if you credited me when you took my comment straight from Engadget ;)
-Matt (original writer)
Re:Still too new (Score:2, Interesting)
Exactly. To determine if people will see battery power saving benefits from using flash vs. hard drives, you need tests that reflect the usage pattern of notebook computers on battery - occasional reads, rare writes, and a lot of idle time. (If your notebook is actually a desktop replacement, then I presume it's plugged in.)
It's the idle time that make a big difference: flash doesn't consume power when idle, whereas with a hard drive you need to either keep that sucker spinning (costing power) or suffer a big performance hit by starting it up for each operation. It's not clear that their benchmarks reflect this usage pattern.
I put a small (4 GB) SSD in my old Vaio SRX77 and get about an extra half hour to 45 minutes of battery life out of it now. Of course, I lot several gigs of storage on the deal, but that's fine - I took a junk machine and for about $70 turned it into something roughly in the class of a Asus Eee on the cheap.
Or even real world intensive use (Score:4, Interesting)
Even when I use something that hits my drive hard, it is far from continuous. In fact flash drives might have a chance to shine here as well as often one of the things that increases activity is the need for random access, which magnetic media isn't all that fast at. For example my harddrive works much harder than it has to when I'm doing audio mixdowns because it has to access multiple wave files at the same time. Most of the time is spent seeking from file to file, it takes comparatively little time to read the actual data needed. Flash, of course, has much faster random access. Thus for something like this it'd be loaded lighter, despite it being an "intense" use.
Re:Still too new (Score:3, Interesting)
Wow, um, you definitely could use some edumacation on how SSDs and hard drives in general work. Here, let me help.
after using Seagate cheap stuff (SATA) and SCSI for years and never seen these things actually fail (besides stupid filesystems)
Then you don't handle very many hard drives. I work in a data center and around 5% of the disks we buy fail within a few months. We don't have one brand in particular that we use because they seem to all fail at about the same rate. (Seagate does have the best warranty and RMA program, though.)
I wait for Seagate, Fujitsu, Hitachi like known brands to ship their SSD rather than being abused by some memory vendor who has no clue about the hard disks to buy some overpriced flash memory fantasy.
Who do you think Seagate, Western Digital, and Fujitsu will buy their memory from? Those companies manufacture hard disks, not memory chips. They have huge investments in the production of mechanical drives. It's possible that some of them might set up memory fabs at some point, but that could still be a long way off because mechanical drives are not going to be completely obsolete for quite some time. In the short term (and possibly long term), they're going to be outsourcing flash chips for their SSDs from lots of companies you've never heard of before.
I also don't know the actual reliability of SSD too. What about journaling? Can it handle? A journal is still needed on SSD drive, what if kernel fails or OS filesystem layer goes nuts? A journal will be in same area of disk and will be written over and over millions of times.
It's too early to tell what the long-term reliability of current SSDs will be, but it's dead-certain that they will improve regardless. (Keep in mind that all early hard disks came with defects on them from the _factory_ and users were expected to format around them, so SSDs already have a good head start in terms of reliability.) SSDs were just introduced and haven't had much real-world testing yet. However, all of the manufacturers have been marketing them as replacements for mechanical hard disks, so clearly they expect the lifespan of an SSD to come close to that of a mechanical disk.
Journaling isn't a concern, because all of these drives implement wear leveling to lengthen the life of the drive.
I could never buy the "speed" claims of SSD
You don't have to buy anyone's claims, look at the numbers yourself. The read speed of SSDs beats the pants off mechanical disks. And I believe they've caught up on write speeds already.
not just because I use very fast SCSI stuff but I actually see the horrible performance of them in my smart phone, HD Camera. It is like performance suicide if someone dares to put a very complex applications to "memory card" instead of phones built in memory.
Err, yeah, I'm pretty sure your bottleneck is going to be the smart phone with it's 200MHz CPU and 0.9MB/sec max transfer rate.
They are trying to ship it before it is a technology fit to general use. Much like some video sites existed while everyone had to struggle with 56K modem.
The problem is that they're hidously expensive. SSDs are just fine for general use. There are people using them that don't have a problem with them. Yes, there are some drawbacks because they're an early technology, but it will get better with time. Remember the first LCD monitors? People said those would never catch on. They were analog only, had a very narrow viewing angle, displayed washed-out colors and horrible refresh rates. They were also hideously expensive but eventually these problems were fixed and price came down until they were comparable with CRTs. In just a couple years, you won't be able to buy a CRT monitor at an affordable price because LCDs have made them obsolete in just about every field.
The same thing will happen with mechanical drives and SSDs.
Re:Not so good benchmark (Score:3, Interesting)
Operating systems still aren't designed around these things, they are designed for physical rotating disks.
How exactly are current OSes designed for physical rotating disks?
You wouldn't design an OS around the hard disk any more than you would design one around the keyboard or power supply. As far as any OS is concerned, /dev/sda is just a block device, no matter whether it's a single-spindle hard disk, solid state disk, or a 42-disk hardware RAID 5. If the SSD needs any special treatment (such as wear-leveling), that function should be abstracted away and implemented in the drive itself, not the OS.