back to article All aboard the flash array train?

A flash train is thundering down the track, coming right at the storage array vendors. Will they step aside, get run over, or leap aboard? About 18 months ago the competitors were Nimbus, a start-up, and Texas Memory Systems (TMS) and Whiptail, all offering all-flash memory arrays. Now these have been joined by Solid Access, …

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Does flash still have a limited number of writes per block?

Does flash still have a limited number of writes per 'block'? If it does...

Assume perfect wear levelling, and assume pretty much the maximum IOPS, with 50/50 split between reads and writes (as a starting point only).

How many months can the array run before something needs replacing (preventively or after error), what is the Field Replaceable Unit, and how much does it cost to replace one?

If ECC (or RAID or whatever) is proposed as a mechanism to reduce cost/risk of failure, how much of a performance impact does it have? Give examples.

Your input would be much appreciated, readers, as it doesn't seem to be in the regurgitated press releases I've seen so far.

I know this stuff is going to be very interesting to some apps, but afaik it does have a downside and ignoring it helps no one (except the vendors and their resellers and...).

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WTF?

Title sometimes goes here

Didn't I read this same article yesterday on El Reg?

Also, Oracle already has the F5100 Flash Array. It was news. What happened to it? Popular or not? Sure was expensive.

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Anonymous Coward

Flash getting closer to disk ?

I saw 3-bit per cell flash a while ago, although it was not ready for Gbyte arrays at the time.

However, all this does is move flash 'nearer' to disk, not 'near' disk. And meanwhile disk is moving on. You can now get 1TB on 2 platters in a 2.5" drive; 18 months ago you were lucky to get half that. Also 3TB is easily available in 3.5" disks, and 2TB is currently the cheapest way to buy disk; the 2TB disks I bought this year cost the same as the 500GB disks I bought a few years ago...

By the time flash gets to where disk is, disk will be somewhere else. I'm sure that moving storage will go eventually, but I don't see it happening soon.

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Go

CRT vs LCD

This is reminiscent of a few years ago when CRT monitors were standard and LCDs on their way. I remember looking forward eagerly to the day we all knew was coming, when LCDs would be the norm and nobody bothered with CRT any more. How far away it seemed. I guess it won't too much longer before we are thinking of spinning disks as somewhat quaint, but antiquated.

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Anonymous Coward

There is a big difference...

...If a monitor failed catastrophically you were unlikley to lose data. All you needed to do was plug in a working monitor.

If a flash disk fails, then unless your backup and DR solutions are good you are hosed.

That's not to say that the same problems wouldn't happen with disk, of course. However, disk is a known technology - I think flash may require a little longer to prove itself.

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FAIL

So nobody wants to answer the question re flash memory write lifetime?

Whoops. Not good, chaps.

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Boffin

I'll answer the question

Sure it wears out., Not that you will ever notice.

In an enterprise setting, with multi 10's of TB arrays it is unlikely that more than a fraction of the array will be changed on any given day. Even if the entire array were changed daily, that would be all of 1K-1.5K overwrites in a 3-5 year lifespan? With a data sheet erase life of 10/100K for MLC/SLC?

The data sheet life is also based on tons of assumptions that might apply to an iPod, but don't apply to a storage array.

The other thing to remember, when the datasheet says the part is good for 10,000 program/erase cycles, it doesn't mean that the part fails at 10,001 erases, it means the maker promised in the WORST CASE that no more than X% of the part will have gone bad by 10K erases. For many parts a lot less than X% will have gone bad. Many parts will last for 2 or 3 or even more times as many erases, the average flash part lasts much much longer than the worst case part.

Finally when you are an iPod and you have one flash die you care very much about the handful of parts which only last as long as datasheet says they will, when you have 1,000's of parts in an array you get to work with the law of large numbers and can depend on getting a much longer than datasheet life from the vast majority of the parts.

So to answer your question.

Sure flash wears out,......

but no enterprise customer should ever be effected by it.

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