Re: SSD + RAID - Mailing list pgsql-performance

From Aidan Van Dyk
Subject Re: SSD + RAID
Date
Msg-id 20100223203435.GV14128@oak.highrise.ca
Whole thread Raw
In response to Re: SSD + RAID  (david@lang.hm)
Responses Re: SSD + RAID  (david@lang.hm)
List pgsql-performance
* david@lang.hm <david@lang.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@highrise.ca                                       command like a king,
http://www.highrise.ca/                                   work like a slave.

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