From: Greg Smith <greg@2ndquadrant.com>
To: Bryan Keller <bryanck@gmail.com>
Cc: pgsql-admin@postgresql.org
Subject: Re: Postgres on NAS/NFS
Date: Wed, 16 Feb 2011 15:56:13 -0500
Message-ID: <4D5C39ED.9040609@2ndquadrant.com> (raw)
In-Reply-To: <E52993F4-A49C-4610-A10D-BFE01545987D@gmail.com>
References: <9424C7B4-672D-4C64-BE6A-699708981C0B@gmail.com>
<AANLkTin8PyrBW4cG__Vmas2+cNB+hWRghULChspt+sxt@mail.gmail.com>
<E52993F4-A49C-4610-A10D-BFE01545987D@gmail.com>
Bryan Keller wrote:
> It sounds like NFS is a viable solution nowadays. I a still going to shoot for using iSCSI, given it is a block-level protocol rather than file-level, it seems to me it would be better suited to database I/O.
>
Please digest carefully where Joe Conway pointed out that it took them
major kernel-level work to get NFS working reliably on Linux. On
anything but Solaris, I consider NFS a major risk still; nothing has
improved "nowadays" relative to when people used to report regular
database corruption running it on other operating systems. Make sure
you read
http://www.time-travellers.org/shane/papers/NFS_considered_harmful.html
and mull over the warnings in there before you assume it will work, too.
I don't think I've ever heard from someone happy with an iSCSI
deployment, either. The only way you could make an NFS+iSCSI storage
solution worse is to also use RAID5 on the NAS.
I'd suggest taking a look at
http://wiki.postgresql.org/wiki/Shared_Storage and consider how you're
going to handle fencing issues as well here. One of the reasons SANs
tend to be preferred in this area is because fencing at the
fiber-channel switch level is pretty straightforward. DAS running over
fiber-channel can offer the same basic features though, it's just not as
common to use a switch in that environment.
--
Greg Smith 2ndQuadrant US greg@2ndQuadrant.com Baltimore, MD
PostgreSQL Training, Services, and 24x7 Support www.2ndQuadrant.us
"PostgreSQL 9.0 High Performance": http://www.2ndQuadrant.com/books
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To: pgsql-admin@postgresql.org
Cc: greg@2ndquadrant.com, bryanck@gmail.com
Subject: Re: Postgres on NAS/NFS
In-Reply-To: <4D5C39ED.9040609@2ndquadrant.com>
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