| From: | Aidan Van Dyk <aidan(at)highrise(dot)ca> |
|---|---|
| To: | david(at)lang(dot)hm |
| Cc: | Ron Mayer <rm_pg(at)cheapcomplexdevices(dot)com>, Bruce Momjian <bruce(at)momjian(dot)us>, Greg Smith <greg(at)2ndquadrant(dot)com>, pgsql-performance <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: SSD + RAID |
| Date: | 2010-02-23 20:34:35 |
| Message-ID: | 20100223203435.GV14128@oak.highrise.ca |
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| Lists: | pgsql-performance |
* david(at)lang(dot)hm <david(at)lang(dot)hm> [100223 15:05]:
> However, one thing that you do not get protection against with software
> raid is the potential for the writes to hit some drives but not others.
> If this happens the software raid cannot know what the correct contents
> of the raid stripe are, and so you could loose everything in that stripe
> (including contents of other files that are not being modified that
> happened to be in the wrong place on the array)
That's for stripe-based raid. Mirror sets like raid-1 should give you
either the old data, or the new data, both acceptable responses since
the fsync/barreir hasn't "completed".
Or have I missed another subtle interaction?
a.
--
Aidan Van Dyk Create like a god,
aidan(at)highrise(dot)ca command like a king,
http://www.highrise.ca/ work like a slave.
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