On 8/24/2011 11:17 AM, Merlin Moncure wrote:
hm, I think they need to reconcile those numbers with the ones on this page: http://www.intel.com/content/www/us/en/solid-state-drives/solid-state-drives-320-series.html 600 write ips vs 3.7k/23k.
They do provide an explanation (and what I find interesting about this document is that they are basically "coming clean" about the real worst-case performance, which I personally find refreshing and encouraging). The difference is that the high number is achieved if the drive does not need to perform a block erase to process the write (this is true most of the time since the capacity is over-provisioned and there is an expectation that GC will have generated free blocks in the background). The low number is the performance under worst-case conditions where the drive is a) full and b) no blocks have been trimmed, and c) GC wasn't able to run yet.
I suspect that in production use it will be possible to predict in advance when the drive is approaching the point where it will run out of free blocks, and hence perform poorly. Whether or not this is possible is a big question for us in planning our transition to SSDs in production.
Anyone using SSDs should be aware of how they work and the possible worst case performance. This article helps with that !
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