Random Read/Write Performance

Arguably much more important to any PC user than sequential read/write performance is random access performance. It's not often that you're writing large files sequentially to your disk, but you do encounter tons of small file reads/writes as you use your PC.

To measure random read/write performance I created an iometer script that peppered the drive with random requests, with an IO queue depth of 3 (to add some multitasking spice to the test). The write test was performed over an 8GB range on the drive, while the read test was performed across the whole drive. I ran the test for 3 minutes.

The three hard drives all posted scores below 1MB/s and thus aren't visible on our graph above. This is where SSDs shine and no hard drive, regardless of how many you RAID together, can come close.

The two Intel drives top the charts and maintain a huge lead. The OCZ Vertex actually beats out the more expensive (and unreleased) Summit drive with a respectable 32MB/s transfer rate here. Note that the Vertex is also faster than last year's Samsung SLC drive that everyone was selling for $1000. Even the JMicron drives do just fine here.

If we look at latency instead of transfer rate it helps put things in perspective:

Read latencies for hard drives have always been measured in several ms, but every single SSD here manages to complete random reads in less than 1ms under load.

Random write speed is where we can thin the SSD flock:

Only the Intel drives and to an extent, the OCZ Vertex, post numbers visible on this scale. Let's go to a table to see everything in greater detail:

4KB Random Write Speed  
Intel X25-E 31.7 MB/s
Intel X25-M 23.1 MB/s
JMicron JMF602B MLC 0.02 MB/s
JMicron JMF602Bx2 MLC 0.03 MB/s
OCZ Summit 0.77 MB/s
OCZ Vertex 2.41 MB/s
Samsung SLC 0.53 MB/s
Seagate Momentus 5400.6 0.81 MB/s
Western Digital Caviar SE16 1.26 MB/s
Western Digital VelociRaptor 1.63 MB/s

Every single drive other than the Intel X25-E, X25-M and OCZ's Vertex is slower than the 2.5" Seagate Momentus 5400.6 hard drive in this test. The Vertex, thanks to OCZ's tweaks, is now 48% faster than the VelociRaptor.

The Intel drives are of course architected for the type of performance needed on a desktop/notebook and thus they deliver very high random write performance.

Random write performance is merely one corner of the performance world. A drive needs good sequential read, sequential write, random read and random write performance. The fatal mistake is that most vendors ignore random write performance and simply try to post the best sequential read/write speeds; doing so simply produces a drive that's undesirable.

While the Vertex is slower than Intel's X25-M, it's also about half the price per GB. And note that the Vertex is still 48% faster than the VelociRaptor here, and multiple times faster in the other tests.

Sequential Read/Write Performance SYSMark 2007
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  • stilz - Friday, March 27, 2009 - link

    This is the first hardware review I've read from start to finish, and the time is well worth the information you've provided.

    Thank you for your honest, professional and knowledgeable work. Also kudos to OCZ, I'll definitely consider the Vertex while making purchases.
    Reply
  • Bytales - Friday, March 27, 2009 - link

    As i read the article, i'm thinking of ways to slow down the down the degrading process. Intel is gonna ship x-25m 320gb this year. If i buy this drive and use it as an OS drive, i will obviously won't need the whole 320GB. Say i would need only 40 to 50 GB. I can make a secure erase (if the drive isn't new), made a partition of 50GB, and leave the remaining space unpartitioned. Will that solve the problem in any way ?
    Another way to solve the problem, would be a method inside the OS. The OS could use a user controlled % of the RAM memory, as a cache for those small 4kb files. Since ram reads and writes are way faster, i think it will also help. Say you got 8GB ram, and use 2gb for this purpose, and then the OS would only have 6gb ram for its use, while 2gb is used for these smaller files. That would increase also the lifespan of the SSD. Can this be possible ?
    Reply
  • Hellfire26 - Thursday, March 26, 2009 - link

    In reference to SSD's, I have read a lot of articles and comments about improved firmware and operating system support. I hope manufacturers don't forget about the on-board RAID controller.

    From the articles and comments made by users around the web, who have tested SSD's in a Raid 0 configuration, I believe that two Intel X25-M SSD's in a RAID 0 configuration would more than saturate current on-board RAID controllers.

    Intel is doing a die shrink of the NAND memory that is going into their SSD's come this fall. I would expect these new Intel SSD's to show faster read and write times. Other manufacturers will also find ways to increase the speed of their SSD's.

    SSD's scale well in a RAID configuration. It would be a shame if the on-board RAID controller limited our throughput. The alternative would be very expensive add-in RAID cards.
    Reply
  • FlaTEr1C - Wednesday, March 25, 2009 - link

    Anand, once again you wrote an article that no one else could've written. This is why I'm reading this site since 2004 and will always do. Your articles and reviews are without exception unique and a must-read. Thank you for this thorough background, analysis and review of SSD.

    I was looking a long time for a solution to make my desktop experience faster and I think I'll order a 60GB Vertex. 200€(germany) is still a lot of money but it will be worth it.

    Once again, great work Anand!
    Reply
  • blackburried - Wednesday, March 25, 2009 - link

    It's referred to as "discard" in the kernel functions.

    It works very well w/ SSD's that support TRIM, like fusion-io's drives.
    Reply
  • Iger - Wednesday, March 25, 2009 - link

    This is the best review I've read in a very long time.
    Thank you very much!
    Reply
  • BailoutBenny - Tuesday, March 24, 2009 - link

    Great in depth article on flash based SSDs. I'm waiting for PRAM though. Reply
  • orclordrh - Tuesday, March 24, 2009 - link

    Very illuminating article, very well written and researched. It made me glad that I didn't pull the trigger on an SSD for my I7 machine and regret not buying OCZ memory! I'm interested in adding an SSD as the scratch disk for Photoshop CS4 to use. I don't really launch applications very often, say once a week on the weekly reboot and keep 6-8 apps open at all times. I have 12GB of memory for that. The benchmarks were very interesting, but what sort of activity does Photoshop scratch usage create? Large files or random writes? What type of SSD would be most cost effective here?
    An SSD does sound better than a SSD!
    Reply
  • semo - Wednesday, March 25, 2009 - link

    wait for ddr3 to enter the mainstream and buy loads of memory.

    use a ramdisk for your adobe scratch area. much faster than ssd and no wear to worry about (not that you would worry that much with modern ssds anyway).

    http://www.ghacks.net/2007/12/14/use-a-ramdisk-to-...">http://www.ghacks.net/2007/12/14/use-a-ramdisk-to-...

    there is also a paid for and more feature rich ramdisk out there. can't remember the name
    Reply
  • strikeback03 - Wednesday, March 25, 2009 - link

    I'll have to check when I get home, but I believe the recommended size for the scratch disk is upwards of 10GB. So would need a motherboard that supports a LOT of RAM to give enough to main memory plus a scratch disk. Reply

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