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Re: Advice sought : new database server

From: Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>
To: Andy Colson <andy(at)squeakycode(dot)net>
Cc: Rory Campbell-Lange <rory(at)campbell-lange(dot)net>, pgsql-performance(at)postgresql(dot)org
Subject: Re: Advice sought : new database server
Date: 2012-03-04 19:51:41
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Lists: pgsql-performance
On Sun, Mar 4, 2012 at 12:45 PM, Andy Colson <andy(at)squeakycode(dot)net> wrote:
> On 03/04/2012 03:58 AM, Rory Campbell-Lange wrote:
>> I'd be grateful for advice on specifying the new server
>> providing about 230GB of usable storage, 150GB of which is on an LV
>> providing reconfigurable space for the databases which are served off an
>> XFS formatted volume.
> Do you mean LVM?  I've heard that LVM limits IO, so if you want full speed
> you might wanna drop LVM.  (And XFS supports increasing fs size, and when
> are you ever really gonna want to decrease fs size?).

It certainly did in the past, I don't know if anyone's done any
conclusive testing on in recently, but circa 2005 to 2008 we were
running RHEL 4 and LVM limited the machine by quite a bit, with max
sequential throughput dropping off by 50% or more on bigger ios
subsystems.  I.e. a 600MB/s system would be lucky to hit 300MB/s with
a LV on top.

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