Random Read/Write Speed

The four corners of SSD performance are as follows: random read, random write, sequential read and sequential write speed. Random accesses are generally small in size, while sequential accesses tend to be larger and thus we have the four Iometer tests we use in all of our reviews.

Our first test writes 4KB in a completely random pattern over an 8GB space of the drive to simulate the sort of random access that you'd see on an OS drive (even this is more stressful than a normal desktop user would see). I perform three concurrent IOs and run the test for 3 minutes. The results reported are in average MB/s over the entire time. We use both standard pseudo randomly generated data for each write as well as fully random data to show you both the maximum and minimum performance offered by SandForce based drives in these tests. The average performance of SF drives will likely be somewhere in between the two values for each drive you see in the graphs. For an understanding of why this matters, read our original SandForce article.

Desktop Iometer - 4KB Random Read (4K Aligned)

Just as we saw in Crucial's move to the m4 it looks like random read speed actually dropped a bit between the SSD 470 and 830. And just as we mentioned before, most desktop workloads don't demand super high 4KB random read performance so if this move was done to improve the 830's behavior elsewhere then it is a worthwhile tradeoff. Even with the drop however the 830 delivers the fastest 4KB random read performance of any high-end drive we've reviewed.

Desktop Iometer - 4KB Random Write (4K Aligned) - 8GB LBA Space

Random write performance has improved tremendously, although it's still noticeably slower than the SF-2281 drives and Crucial's m4. Similar to 4KB random read performance, there are diminishing returns beyond a certain level. Intel tends to have the right idea in how best to deal with random writes: work slower but clean up along the way, vs. write as fast as possible and rely on TRIM/idle garbage collection to improve performance later on. I've become wary whenever I see ultra high 4KB random write performance because it usually means that fragmentation can be a problem over time.

SandForce's numbers are high here because the workload is easily compressible, which is usually the case for desktop random writes as they tend to be table updates.

Many of you have asked for random write performance at higher queue depths. What I have below is our 4KB random write test performed at a queue depth of 32 instead of 3. While the vast majority of desktop usage models experience queue depths of 0 - 5, higher depths are possible in heavy I/O (and multi-user) workloads:

Desktop Iometer - 4KB Random Write (8GB LBA Space QD=32)

We don't see huge scaling with increasing queue depths from any of these drives really, with the exception of the SandForce solutions. Remember for the SF-2281 extra IO doesn't actually result in more writes to NAND, just a higher compression ratio which results in better performance with very little added work. I suspect SandForce's controllers could do very well in high load enterprise environments as a result. I've been working on an enterprise workload suite to figure that out...

Sequential Read/Write Speed

To measure sequential performance I ran a 1 minute long 128KB sequential test over the entire span of the drive at a queue depth of 1. The results reported are in average MB/s over the entire test length.

Desktop Iometer - 128KB Sequential Read (4K Aligned)

Although there are diminishing returns for ultra high random read/write operations on a desktop system, large sequential reads still scale quite well. If you do any amount of large file copying from your SSD to another SSD or file server you'll want to pay attention to these numbers here. Samsung manages to dethrone Intel at the top of our charts here with a very respectable 411.5MB/s.

Desktop Iometer - 128KB Sequential Write (4K Aligned)

Sequential write speed is also still very important, again for those large file transfers. Despite the importance of random read/write IO the majority of desktop access patterns are still governed by sequential throughput. For an SSD to truly excel it needs good performance in all four of these categories. Thankfully for Samsung's sake, the SSD 830 delivers.

The Drive AS-SSD Incompressible Sequential Performance


View All Comments

  • spudit88 - Saturday, September 24, 2011 - link

    Great review- I've installed several of the 470 Series and they have been very reliable. I don't believe we have had issues with any of them. These are mostly going into corporate laptops, so the fastest SSD's are not always the best option. I've stuck mainly with Samsung or Intel for reliability reasons. We are just now starting to deploy more laptops with 6Gb/s interfaces, it's good to know there are more choices out there....particularly with a larger drive option of 512GB. Reply
  • know of fence - Saturday, September 24, 2011 - link

    The Sizes of these drives are multiples of 2, (64,128), does this imply that GB means the same as GB inside Windows, Gibibyte a.k.a 2^30 Byte or 1.073*10^9 Byte. Same as with RAM.

    Or does "GB" refering to SSD Sizes actually mean something completely different than MB (per second) in Speed Benchmarks.
  • know of fence - Saturday, September 24, 2011 - link

    Sorry, It's all explained. Still a bummer, though. Reply
  • buzznut - Saturday, September 24, 2011 - link

    Two years ago, Samsung seemed convinced the way of the future was hybrid drives that combined the best of both worlds-the capacity of a mechanical with the performance of an SSD. They had a lot of reliability problems with these drives, I expect that's why there aren't more of these drives on the market.

    What I am wondering is has Samsung completely abandoned this idea? What about other manufacturers? Do you think that the cost of producing such drives makes it impractical?

    Some of the average performing SSDs have come down to the $1/GB price point, which is seemingly the magic number for those folks still hanging on desperately to their mechanical drives. Now I hear these same folks complaining about reliability being the main issue keeping them from adopting new technology, and they aren't wrong.

    I haven't had any issues with my SSDs, I find them to be extremely reliable and now I don't think I could go back for a system drive. Initially I had an X25 40GB, now a 128GB Vertex III. So the reliability of the Samsung drives is refreshing news and I sincerely hope the drives will be priced competitively because I'd really like to see them succeed with this.

    I still think, if implemented properly, that there is a market for hybrid drives. Don't know that anyone is willing to risk that though.
  • Evonick - Saturday, September 24, 2011 - link

    I'm curious if anyone knows the actual time involved for idle time garbage collection, and whether that process is equivalent to TRIM? Anand mentions "overnight" in the review, but does itgc really take 8 hours? And when does it start? After 3 minutes of idle or 3 hours? And when the itgc is completed, how does the drive perform compared to a TRIMmed drive? Reply
  • FunBunny2 - Saturday, September 24, 2011 - link

    -- I've been working on an enterprise workload suite to figure that out...

    In order for this to be "real", encrypted data input is required. The reason is that relational databases in Enterprise are increasingly configured with encryption.
  • tpi2007 - Saturday, September 24, 2011 - link

    I Anand, congratulations for the review and the video review, both of which I enjoyed very much.

    I was looking at the power consumption figures and was wondering if Samsung's higher numbers could have to do with their use of DDR2 for cache ? And by that I mean two things:

    1. The fact that it's much bigger than Intel's for example should add to the power consumption, adding to the fact that they store user data, which probably means more data being written and read from all the time, increasing power consumption;

    2. The fact that it's DDR2. Is it low power DDR2 or just normal 1.8v DDR2 ? That could explain the higher power consumption to a certain extent too. What if Samsung were to use low power 1.35 or even better, 1.25v DDR3L ?

    Best regards,

  • FunBunny2 - Saturday, September 24, 2011 - link

    Along similar lines: why is there not a power loss test in the suite? There appears to be no superCap on the board, yet the part uses "massive" amounts of DRAM with user data. This looks like a bleeding Achille's heel. Reply
  • enigma80 - Saturday, September 24, 2011 - link

    This worried me too. 256MB of user data in a limbo?

    It would be importante to test a power loss amid writing to the drive and check the data on the drive.
  • Obsoleet - Thursday, January 19, 2012 - link

    Excellent points. I'd like to hear an answer to this.

    The more I read, the more I feel Intel is the way to go.. even vs this Samsung and M4s.

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