On Fri, Aug 27 at 6:16, Eff Norwood wrote:
David asked me what I meant by "filled up". If you make the unwise
decision to use an SSD as your ZIL, at some point days to weeks
after you install it, all of the pages will be allocated and you
will suddenly find the device to be slower than a conventional disk
drive. This is due to the way SSDs work. A great write up about how
this works is here:
http://www.anandtech.com/show/2738/8
While it's an interesting writeup, I think some assumptions are being
made that may not be quite correct. In the case of a ZIL, with a
relatively small data set (< 1GB typically) on your SSD, if designed
correctly, drive will always be running with many gigabytes of
"scratch" area available.
Fully written SSDs may write more slowly than partially written SSDs
in some workloads, but I wouldn't expect a ZIL usage model to create
the scenario you linked due to the limited data set size.
--
Eric D. Mudama
edmud...@mail.bounceswoosh.org
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