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)

As we saw in our RevoDrive 3 X2 review, low queue depth random read performance doesn't really show much of an advantage on these multi-controller PCIe RAID SSDs. The Z-Drive R4 comes in a little faster than the RevoDrive 3 X2 but not by much at all. Even a single Vertex 3 does just fine here.

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

Random write performance tells a similar story, at such low queue depths most of the controllers aren't doing any work at all. Let's see what happens when we start ramping up queue depth however:

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

Surprisingly enough, even at a queue depth of 32 the Z-Drive R4 is no faster than the RevoDrive 3 X2. In fact, it's a bit slower (presumably due to the extra overhead of having to split the workload between 8 controllers vs just 4). In our RevoDrive review we ran a third random write test with two QD=32 threads in parallel, it's here that we can start to see a difference between these drives:

It's only at ultra high queue depths that the Z-Drive can begin to distance itself from the RevoDrive 3 X2. It looks like we may need some really stressful tests to tax this thing. The chart below represents the same data as above but in IOPS instead of MB/s:

271K IOPS...not bad.

The Card Sequential Read/Write Speed


View All Comments

  • caliche - Wednesday, September 28, 2011 - link

    I am sure he is referring to the previous versions of the z-drive, which is all you can use as an indicator.

    I am an enterprise customer. Dell R710s and two Z-Drive R2 M84 512GB models, one in each. I have had to RMA one of them once, and the other is on it's second RMA. They are super fast when they work, but three failures across two devices in less than a year is not production ready. We are using them in benchmarking servers running Red Hat Enterprise 5 for database stores, mostly read only to break other pieces of software talking to it. Very low writes.

    But here is the thing. When they power on, one or more of the four RAID pieces is "gone". This is just the on board software on the SSD board itself, no OS, no I/O on it at all besides the power up RAID confidence check. Power on the server, works one day, next day the controller on the card says a piece is missing. That's not acceptable when you are trying to get things done.

    In a perfect world, you have redundant and distributed everything with spare capacity and this is not a factor. But then you start looking at dealing with these failures and you start to ask yourself is your time better spent on screwing around with an RMA process and rebuilds or optimizing your environment?
  • ypsylon - Thursday, September 29, 2011 - link

    Nobody in the right frame of mind using SSD in enterprise segment (not even interested in them as consumer drives, but that is not the issue here). SSDs are just as unreliable as normal HDDs with ridiculous price point. You can lose all of data much quicker than from normal HDD. RAID arrays built from standard HDDs are just as fast as 1 or 2 "uber" SSDs and cost fraction of a SSD setup (often even including cost of the RAID controller itself). Also nobody running large arrays in RAID0 (except maybe video processing). RAID0 is pretty much non-existent in serious storage applications. As a backup I much more prefer another HDD array than unreliable, impossible to test, super-duper expensive SSD.

    You can't tests NAND reliability. That is the biggest problem of SSDs in business class environment. Because of that SSD will whiter and die in the next 5-10 years. SSDs are not good enough for industry, if you can't hold on to big storage market then no matter how good something is, it will die. Huge, corporate customers are key to stay alive is storage market.
  • Zan Lynx - Thursday, September 29, 2011 - link

    You are so, so wrong.

    Enterprises are loving SSDs and are buying piles of them.

    SSDs are the best thing since sliced bread if you run a database server.

    For one thing, the minimum latency of a PCIe SSD 4K read is almost 1,000 times less than a 4K read off a 15K SAS drive. The drive arrays don't even start to close the performance gap until well over 100 drives, and even then the drive array cannot match the minimum latency. It can only match the performance in parallel operations.

    If you have a lot of operations that work at queue depth of 1, the SSD will win every time, no matter how large the disk array.
  • leonzio666 - Wednesday, November 02, 2011 - link

    Bear in mind though, that enterprises (real heavy weights) probably preffer something like fusion-io io-drives which btw are the only ssd`s running in IBM driven blade servers. With speeds up to 3 Gb/s and over 320 k IOPS it`s not surprising they cost ca 20k $$ per unit :D So it`s not true that SSD`s in general are not good for the enterprise segment. Also, and this is hot - these ssd use SLC NAND... Reply
  • MCS7 - Thursday, September 29, 2011 - link

    I remember Anand doing a VOODOO 2 card review (VIDEO) way way way back at the turn of the millenium! Oh boy..we are getting OLD....lol take care all Reply
  • Googer - Thursday, September 29, 2011 - link

    Statistics for CPU usage would have been handy as some storage devices have greater demands for the CPU than others. Even between various HDD makes, CPU use varies. Reply
  • alpha754293 - Thursday, September 29, 2011 - link

    Were you able to reproduce the SF-2xxxx BSOD issue with this? or is it limited to just the SF-2281? Reply

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