On 04/06/2011 08:22 PM, Scott Carey wrote:
> Simple power failure tests demonstrate that you lose data with these
> drives unless you disable the cache. Disabling the cache roughly drops
> write performance by a factor of 3 to 4 on G1 drives and significantly
> hurts wear-leveling and longevity (I haven't tried G2's).
>
Yup. I have a customer running a busy system with Intel X25-Es, and
another with X25-Ms, and every time there is a power failure at either
place their database gets corrupted. That those drives are worthless
for a reliable database setup has been clear for two years now:
http://www.mysqlperformanceblog.com/2009/03/02/ssd-xfs-lvm-fsync-write-cache-barrier-and-lost-transactions/
and sometimes I even hear reports about those drives getting corrupted
even when the write cache is turned off. If you aggressively replicate
the data to another location on a different power grid, you can survive
with Intel's older drives. But odds are you're going to lose at least
some transactions no matter what you do, and the risk of "database won't
start" levels of corruption is always lingering.
The fact that Intel is making so much noise over the improved write
integrity features on the new drives gives you an idea how much these
problems have hurt their reputation in the enterprise storage space.
--
Greg Smith 2ndQuadrant US greg@2ndQuadrant.com Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.us
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