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January 20, 2010


marc farley

Hi Chuck, There's no doubt that flash SSDs will change array configurations. They will make capacity planning much more interesting too. A two tier configuration doesn't leave much room for error unless you tend to oversize the SSD tier to accommodate worst case performance demands. As long as SSDs are viewed as being expensive, there will be some resistance to overbuying them. That could be bad. So while I understand the desire to drive towards a polar (speed vs capacity) device model, spinning FC drives will probably stay around for awhile. Once dynamic performance tiering software like FAST has been proven, the performance/configuration planning should become less experimental and more predictable. But that's not going to be in 2010.

Chuck Hollis

Hi Marc -- nice to see you back in the mix again ...

So, we could each speculate on rates of adoption, but I don't think there's much disagreement that a new model is emerging.

One think I'd like to point out, though ...

Let's say you "get it wrong" and don't get enough enterprise flash for your array, and (theoretically) performance suffers as a result.

Answer? Buy another enterprise flash drive, pop it in, and the array automatically puts it to work where it's needed.

Bottom line: far less need to "get it right" up front.

-- Chuck


I guess I did good when I opted for a 100% SATA array more than a year ago tossing out the idea from a competing vendor wanting to mix some 10k RPM disks and SATA disks.

Just today I was looking at some of the performance stats of my array, and have been pretty surprised to see the system as a whole peaking out at over 100 IOPS/disk(average over all disks), with some disks hitting 125 IOPS at peak load. I really didn't think that was possible for random workloads. Perhaps the firmware update to the disks a few days ago turbo charged them.

I also do like the ability to add new disks as larger sizes come out and stripe my data across all disks(e.g. same RAID set striped over 750GB, 1TB and 2TB disks transparently). Sub-disk raid is where it's at for me!

I hope I'm able to somehow evaluate auto tiering with SSD some time this year, I'm not convinced yet at least for our workloads that it will be worth the investment, because I suspect the amount of time the controllers need to "see" that there is hot data and move it to the right place by the time it's moved it may be finished using it already.

If SSD could operate in more of a traditional cache I'd like that a lot more myself. I could see this design being beneficial to array vendors that integrate controllers into their disk shelves(say Xiotech, or Isilon), put a bunch of SATA disks in, and then a couple mirrored SSDs, and have all of the data movement from/to that shelf pass through those SSDs as a massive cache. I bet you wear the SSDs out a lot faster this way but that's what warranty exchange is for right?

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Chuck Hollis

  • Chuck Hollis
    SVP, Oracle Converged Infrastructure Systems

    Chuck now works for Oracle, and is now deeply embroiled in IT infrastructure.

    Previously, he was with VMware for 2 years, and EMC for 18 years before that, most of them great.

    He enjoys speaking to customer and industry audiences about a variety of technology topics, and -- of course -- enjoys blogging.

    Chuck lives in Vero Beach, FL with his wife and four dogs when he's not traveling. In his spare time, Chuck is working on his second career as an aging rock musician.

    Warning: do not ever buy him a drink when there is a piano nearby.

    Note: these are my personal views, and aren't reviewed or approved by my employer.
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