From: Mark Kirkwood <mark.kirkwood@catalyst.net.nz>
To: Bruce Momjian <bruce@momjian.us>
Cc: Gregg Jaskiewicz <gryzman@gmail.com>
Cc: Greg Smith <greg@2ndquadrant.com>
Cc: postgres performance list <pgsql-performance@postgresql.org>
Cc: Niels Kristian Schjødt <nielskristian@autouncle.com>
Subject: Re: New server setup
Date: Fri, 15 Mar 2013 10:37:55 +1300
Message-ID: <51424333.608@catalyst.net.nz> (raw)
In-Reply-To: <20130314185424.GA28770@momjian.us>
References: <4D6D1410-2208-4DAA-BD64-69BE1FD94E55@autouncle.com>
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<20130314185424.GA28770@momjian.us>
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On 15/03/13 07:54, Bruce Momjian wrote:
> Only use SSDs with a BBU cache, and don't set SSD caches to
> write-through because an SSD needs to cache the write to avoid wearing
> out the chips early, see:
>
> http://momjian.us/main/blogs/pgblog/2012.html#August_3_2012
>
I not convinced about the need for BBU with SSD - you *can* use them
without one, just need to make sure about suitable longevity and also
the presence of (proven) power off protection (as discussed previously).
It is worth noting that using unproven or SSD known to be lacking power
off protection with a BBU will *not* save you from massive corruption
(or device failure) upon unexpected power loss.
Also, in terms of performance, the faster PCIe SSD do about as well by
themselves as connected to a RAID card with BBU. In fact they will do
better in some cases (the faster SSD can get close to the max IOPS many
RAID cards can handle...so more than a couple of 'em plugged into one
card will be throttled by its limitations).
Cheers
Mark
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Cc: mark.kirkwood@catalyst.net.nz, bruce@momjian.us, gryzman@gmail.com, greg@2ndquadrant.com, nielskristian@autouncle.com
Subject: Re: New server setup
In-Reply-To: <51424333.608@catalyst.net.nz>
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