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Performance Showdown - SSDs vs. HDDs
Lucas123 writes "Computerworld compared four disks, two popular solid state drives and two Seagate mechanical drives, for read/write performance, bootup speed, CPU utilization and other metrics. The question asked by the reviewer is whether it's worth spending an additional $550 for a SSD in your PC/laptop or to plunk down the extra $1,300 for an SSD-equipped MacBook Air? The answer is a resounding No. From the story: "Neither of the SSDs fared very well when having data copied to them. Crucial (SSD) needed 243 seconds and Ridata (SSD) took 264.5 seconds. The Momentus and Barracuda hard drives shaved nearly a full minute from those times at 185 seconds. In the other direction, copying the data from the drives, Crucial sprinted ahead at 130.7 seconds, but the mechanical Momentus drive wasn't far behind at 144.7 seconds."
In typical use most of the time is spent seeking, not just reading or writing sequential blocks. The Windows XP disk IO is especially brain damaged in this regard (does not even try to order or prioritize disk I/O). Copying DVD images from one drive another is not typical use case.
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Unfortunately there's no comparisons of battery life and speed tests with fragmented files.
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Dunno about the author of this article, but got an "SSD" (hello buzzword) to get rid of the noise, the heat, and the annoying spin-up delay. A compactflash card doesn't cost eleventy billion dollars either.
c++;
Computerworld compared four disks, two popular solid state drives and two Seagate mechanical drives, for read/write performance, bootup speed, CPU utilization and other metrics.
But of course not the metrics that really matter, which SSD's vastly excel at and make them worth the price for many people: MTBF, power consumption, ruggedness and noise level.
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Too bad he didn't include power consumption. If I'm going to use an SSD for anytime soon, it will be in a laptop where power is my key concern. Performance is more of a desktop/high end issue right now.
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IMHO, performance is not the critical factor regarding SSD. Power usage, and mostly no-moving-part (quiet and rugged) is why you want SSD in your laptop.
But on the performance front, they compared with 7200RPM hard drives, last time I checked (admittedly a while ago) most laptop are outfitted with 5400RPM drives.
Am I the only one questioning why these devices are implemented using a mechanical drive interface? Maybe it's a negligible cost, but to me it would seem that a memory bus optimized for flash memory would be a better way to go, than trying to piggy-back a mechanical drive's bus. How much faster could these be if their existence was planned into, say Intel's chipsets?
They only tested burst speeds, there was no random access testing.
SSD works best when accessing files randomly.
You really have to look deep into the advertising sometimes. Only a trained person willing to do the math on these would be able to see the differences. Clearly, these devices have a legitimate purpose and place, but at this point in time, its not in the client computer. The speeds need to come up to be really practical.
Now a good purpose for these might be in desktop bound short-stack storage arrays instead of that large tera-byte drive array. They're just quick enough for data retention backups off of the mechanical drives in the client PC.
Another use is small-scale server apps that usually are bound into hardware in some form of internet controllable appliance. Speed isn't really a major factor here for this and these would potentially work well.
Just my opinion. Subject to change.
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As any sysadmin knows, on a busy server what creams the disk isn't Megabytes per second, it is IO transactions per second.
;-)
According to the article the Crucial SSD has an access time of 0.4 ms which equates to 2500 IOs/s as compared to the Barracuda HDD with 13.4 ms access time which equates to a mere 75 IOs/s.
So for servers SSDs are 33 times better!
Bring them on
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Two things: first, booting is ideally going to be largely sequential reads because OS X caches files used in the boot process in order to speed up the boot by removing random access. SSD's have an advantage over hard drives in random reads because there's comparatively no seek time. So I wouldn't expect to see a huge advantage. Secondly, I'm not going to be using my macbook air's tiny SSD drive for analog video capture or something anyway, so high write speed is really not that relevant to me. On the other hand the thing is supposed to be light and use little battery, so SSD seems like it wins for the reasons it was used. Also, the tests bear out a higher average read speed, which is also what I would have expected. I don't see anything surprising here.
We installed one of these for processing millions of small, read-only database transactions. The database only gets written once a day, but is too big for efficient cacheing. Even with a U320 15k drive we were still suffering, only being able to run about 700/min. With a flash drive, we're running over 25,000/min, peaking at 50,000/min. But the weekly copy of the database takes about 20 minutes, vs the 3 or 4 minutes it used to take.
- p
I don't have a
That's true, but is almost a technicality with today's processors and video cards. With anything but the slowest ultra-portables, having a hd running just doesn't suck up much juice. A Seagate Momentus (5400rpm) takes between 1.9 and 2.3W when reading/writing/seeking, and only 0.8 watts when idle (not standby - that's .2W). Given a typical laptops with between 50 and 80 Wh batteries and a 2 to 3 hour charge life, you're HD comprises about 3% of the average draw at idle, and about 7-8% at full tilt - for those of you running active SQL servers on your lappies. If I give you 30% at non-idle, it's about 4%. That's more power than with a SSD at 0.2W, but it's really only about 4 to 6 minutes of extra time on a charge.
Is it just my observation, or are there way too many stupid people in the world?
There are already drives that have platters and flash. They cache frequently used files in flash and bootup files when you shut down.
Huh. I've always thought that the cache on Hard drives was amazingly small. 16MB? Heck, give me a drive with at least a gigabyte of cache. When I boot up my computer, it should just start reading any sectors that have been used frequently.
Wrong, this myth simply will not go away. All modern drives have write leveling technology built in. Also unlike a mechanical drive which generally fails on read, SSDs fail on write which allows the drive itself to trap all failures, and redirect the bytes to another unused sector. Anyone who care about performance shuts off atime as it is.
I haven't used any swapspace for years on my desktops, memory is so cheap now that there's no point. On my servers, of course, but then again it's 99.9% unused.
For example, this thinkpad has 1.25GB RAM, and I've seen at most 300MB used. Then again, I don't run Vista.
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My apologies for a long post. There will be some adverts embedded, but I will try to keep things informative.
The reason that Flash SSDs act "wierd" in benchmarks is that they have asymmetric performance patterns when reading and writing. Particularly with random operations, this asymmetry is huge. Here are a couple of example "drives":
* Mtron 7000 series: >14,000 4K random reads. ~130 4K random writes.
* SanDisk 5000 series: ~7,000 4K random reads. 13 4K random writes.
* Cheap CF card or USB stick: ~2,500 4K random reads. 3.3 4K random writes.
This is a 100:1 performance deficit when doing random writes versus the random reads. This has some really weird impacts on system performance. For example, if you run Outlook and tell it to "index" your system, it will build a 1-4 GB index file in-place with 100% random writes. If you do this on a hard disk, the job takes a long time and drags down your laptop, but the operation is still pretty smooth. Do the same think on an SSD and the system slugs to molasses. One of our customers described it as "totally unusable" with 2+ minutes to bring up task manager. What happens is that the fast reads allow the application to dirty write buffer faster and this then swamps system RAM, you get a 100+ deep write queue (at 13/sec), and you want to throw the machine off of a bridge.
This fix as some have described it is not some magic new controller glue or putting the flash closer to the CPU. It is organizing the write patterns to more closely match what the Flash chips are good at. Numerous embedded file systems like JFFS do this, but they are really designed for very small devices and are more concerned with wear and lifespan issue than performance.
Now here comes the advert (flames welcome). A little over 2 years ago, I wrote a "block translation" layer for use with Flash storage devices. It is somewhat similar to a LogFS, but it is not really a file system and it does not play be all of the rules of a LogFS. It does however remap blocks and linearize writes. Thus it plays well with Flash. It also appears to be an "invention", and thus my patent lawyer is well paid.
The working name of the driver layer itself is "Fast Block Device" (fbd) and the marketing name is "Manged Flash Technology". And what this does is to transparently map one block device into another view. You can then put whatever file system you want into the mix.
In terms of performance, it is all about bandwidth. Build a little raid-5 array with 4 Mtron drives and you will get over 200 MB/sec of sustained write throughput. With MFT in place, this directly translates into 50,000 4K random writes/sec. Even better, you tend to end up with something that is much closer to symmetric in terms of random read/write performance.
MFT is production on Linux (it has actually been shipping since last summer) and is in Beta test on Windows. It works with single drives as well as small to medium sized arrays. It does work with large arrays, but the controllers don't tend to keep up with the drives, so large arrays are useful for capacity but don't really help performance a lot. Once you get to 50,000 IOPS it is hard for the controllers to go much faster.
Consumer testing with MFT tends to produce some laughable results. We ran PCMark05's disk test on it and produced numbers in the 250K range. This was with a single Mtron 3025. Our code is fast, but we fooled the benchmark in this case.
There are several white papers on MFT posted in the news link of our website:
http://managedflash.com/
My apologies for the advert, but I see a lot of talk about SSDs without actually knowing what is going on inside.
I am happy to answer any questions on-line of off.
Doug Dumitru
EasyCo LLC
610 237-2000 x43
http://easyco.com/
http://managedflash.com/
http://mtron.easyco.com/
Well, I can supply my own experiences for you, after using a 32GB Samsung SSD for a year, and a 64GB Samsung SSD for several months...
1) Mine have been formatted NTFS, running Windows XP (and additionally Apple HFS Journaled recently when experimenting with OS X). I do not defragment the SSD, there is no point. Read speeds have always been better than write speed, but I see no difference in performance over time.
2) Both of the drives I have are fully functional, even though I abused the 32GB one mercilessly. That laptop has only 1GB of RAM and I would run so many programs that things were swapping constantly for the past year.
3) The 32GB SSD has been through airport scanners approximately 50 times now, no problems. The 64GB is too new, only travelled a few times so far.
4) My laptops are always on the go, brought into many factories as a consultant. While in my bag it has taken falls down sets of stairs. The laptop itself (a Fujitsu P1610) has been dropped from a height of 3.5 to 4 feet onto a metal catwalk while running with no adverse affects (other than a few scuffs and dents on the corners).
5) Not sure how well they stand up to static, but it has stood up well to a variety of high EM fields, and high/low temperatures. No data loss. I have had regular hard disks die from working next to large transformers (and their magnetic fields) for an afternoon.
Hope that helps you. For my line of work, they have been incredible. I used to go through 3 or 4 laptop hard disks per year due to various issues. Now the only reason I bought the 64GB SSD is increased storage capacity.
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I just ordered a new laptop, and it has an ExpressCard slot into which I could drop 4 or 8 GB of solid-state disk at a reasonable price. That could serve as a giant cache, one that unlike RAM could be safely used as a write cache.
It seems like there would be a clever way to treat the SSD plus the regular hard drive as one unit so that the hard drive could be spun down for hours of normal working situations, giving a giant extension of battery life.
Anybody heard of a virtual block device or special filesystem that would take advantage of this in Linux?
All the brand notebooks with SSD options use first generation SSDs. These have the shattering access speeds, high durability, no noise, and power efficient benefits, but read/write performance is still mediocre.
The second generation SSDs would cost you more than a whole notebook, but have significant performance improvements:
Memoright GT vs Mtron vs Raptor vs Seagate
Memoright nails it. It is easily twice as fast as what Mac puts in their notebooks.
If you *really* want an SSD, buy one separately and install it yourself. You will not be disappointed.
BTW the file indexing that causes SSDs to slow cause HDDs to slow as well. Many people have reported unbearable slowdown, and that is with HDDs. I am sure anything slower than that would make you want to return the whole thing, but this can be fixed. Most people will tell you to just turn it off. Google has also complainted about Microsoft pre-installing an indexing system that sucks.