From: Joshua D. Drake <jd@commandprompt.com>
To: Greg Smith <greg@2ndquadrant.com>
Cc: Bryan Keller <bryanck@gmail.com>
Cc: pgsql-admin@postgresql.org
Subject: Re: Postgres on NAS/NFS
Date: Wed, 16 Feb 2011 13:12:39 -0800
Message-ID: <1297890759.991.154.camel@jd-desktop> (raw)
In-Reply-To: <4D5C39ED.9040609@2ndquadrant.com>
References: <9424C7B4-672D-4C64-BE6A-699708981C0B@gmail.com>
<AANLkTin8PyrBW4cG__Vmas2+cNB+hWRghULChspt+sxt@mail.gmail.com>
<E52993F4-A49C-4610-A10D-BFE01545987D@gmail.com>
<4D5C39ED.9040609@2ndquadrant.com>
On Wed, 2011-02-16 at 15:56 -0500, Greg Smith wrote:
> 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.
In short, use DAS or a SAN. iSCSI suffers from all kinds of performance
issues and NFS is just Michael Myers scary.
With DAS systems able to handle up 192 drives over 6Gb/s a second these
days, combined with a volume manager you can solve a lot of problems
without breaking the bank.
JD
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To: pgsql-admin@postgresql.org
Cc: jd@commandprompt.com, greg@2ndquadrant.com, bryanck@gmail.com
Subject: Re: Postgres on NAS/NFS
In-Reply-To: <1297890759.991.154.camel@jd-desktop>
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