Setting expectations for SSDs versus Flash

Nomenclature: SSD is a physical device that plugs into an electrical disk slot. Flash is a PCIe card. Both use the same underlying back end storage technology (flash chips of SLC, MLC, and related).
I’ve had a while to do some testing with a large number of SSD units in a single device. I can give you a definite sense of what I’ve been observing.
First: SSDs are, of course, fast for certain operations.
Second: there’s a whole lotta er … marketing numerology … around SSDs.
Ok. So imagine we have 48x very late model Sandforce 22xx equipped SSDs, in a single chassis. Call this thing an SSD array. Imagine that we’ve done some experimentation on various RAID cards. Including some from a vendor that has not been announced/released. Including some dumber HBAs.
If we believe the underlying theory behind SSDs, and aggregates of the same, for reasonable configurations of SSD (that does not mean RAID0s, but RAID5’s with a smaller chunk size), we should be able to approach the theoretical maximum number of IOPs, assuming that the RAID calculation engine can keep up with the SSD.
This assumption is, sadly, incorrect.
Theoretical maximum IOP rate for this unit, assuming the vendors don’t … er … embellish too badly … is about 2.4M IOPs. After putting them into RAID5’s best possible case should be 2.1M IOPs.
What do we achieve?

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"Evolution" for Microsoft HPC

This is old news at this time, but Microsoft has moved its HPC group into their Cloud groups.
I’ve talked in the past about critical business decisions that need to be addressed over time, as a business matures, and a product line is given time to sink or swim.
At the end of the day, a business has to make hard decisions about what products to introduce, which to end-of-life, which to grow independently, which to fold into other initiatives. In a general sense, businesses exhibiting rapid growth, you support, and support hard. You give them resources, you feed them additional capital.
You don’t fold them into other initiatives.

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Not surprised … IBM pulls plug on Blue Waters

I say I am not surprised for their reasoning … not that I had an inkling that they would do this before hand.
Basically they pulled the plug because the costs were growing far faster than they planned, and they couldn’t afford to deliver the machine at the requested price. Which makes perfect sense to a business that has to consider profit and loss, but maybe not so much sense to research groups that want things.
I’ve said many, many times … that really bad deals can kill good companies. Not that IBM would be brought down by one bad deal, but fundamentally, IBM has to tell its owners (stock holders) what it did in its business and explain to them their results, every quarter.
Imagine, having to explain a deal that cost you $300M and you only received $30M for it. Or even $60M.
Yeah, someone high up would get fired for that. No, lots of people would get fired for that.
IBM made the right business decision. They are, after all, a business.

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Rethinking RAID for SSDs

SSD units are fast, well, depending upon design, controller and other things. Sandforce units use a compression and overprovision technology to reduce write amplification. SSD units do writes, optimally, in erase block sizes. This suggests that your RAID chunk size should be a multiple of the erase block size. This is a good thing. The … Read moreRethinking RAID for SSDs

OT: and on a happy personal note …

… both my daughter and I were promoted to yon-kyu (green belt) in Isshinryu. Took me longer than I liked, but the specific kata we were learning was complex. Ok, it looks simple, but … it really … really … isn’t. There is great subtlety in it. Mastering this takes a while. The moves took me about a month. The rest took me much longer.
Here is one of the style’s leadership (10th Dan) showing how to do this

Our version is slightly different, but not by much.
This is a different but closer version to what we do

Read moreOT: and on a happy personal note …