On 7/18/2013 6:17 PM, Lists wrote:
> Main thing is DO NOT EVEN THINK OF USING CONSUMER GRADE SSDs. SSDs are a
> bit like a salt shaker, they have only a certain number of shakes and
> when it runs out of writes, well, the salt shaker is empty. Spend the
> money and get a decent Enterprise SSD. We've been conservatively using
> the (spendy) Intel drives with good results.
and not all Intel drives have the key features of supercap backed cache,
and reliable write-acknowlegement behavior you want from a server.
that 95% (20:1) only applies to a SSD compared with a single desktop
grade (7200rpm) disk.
do note, you can easily build proper SAS raids that are just about as
fast as a single SSD when used for write intensive database OTLP
operations, whether measured in raw disk IOPS or transactions/second,
and they are many times bigger. SSD's have the biggest advantage over
a single spinning disk in random read performance.
one funny thing I've noted about various SSD's. when they are new,
they benchmark much faster than after they've been in production use.
expect a several times slowdown in write performance once you've written
approximately the size of the disk worth of blocks. NEVER let them
get above about 75% full.
--
john r pierce 37N 122W
somewhere on the middle of the left coast
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