Message-ID: <519991EB.8010208@2ndQuadrant.com>
Date: Sun, 19 May 2013 23:00:59 -0400
From: Greg Smith <greg@2ndQuadrant.com>
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To: Tomas Vondra <tv@fuzzy.cz>
CC: pgsql-performance@postgresql.org
Subject: Re: Reliability with RAID 10 SSD and Streaming Replication
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On 5/16/13 8:06 PM, Tomas Vondra wrote:
> Have you considered using a UPS? That would make the SSDs about as
> reliable as SATA/SAS drives - the UPS may fail, but so may a BBU unit on
> the SAS controller.

That's not true at all.  Any decent RAID controller will have an option 
to stop write-back caching when the battery is bad.  Things will slow 
badly when that happens, but there is zero data risk from a short-term 
BBU failure.  The only serious risk with a good BBU setup are that 
you'll have a power failure lasting so long that the battery runs down 
before the cache can be flushed to disk.

-- 
Greg Smith   2ndQuadrant US    greg@2ndQuadrant.com   Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.com


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