From: Anj Adu <fotographs@gmail.com>
To: Greg Smith <greg@2ndquadrant.com>
Cc: pgsql-admin@postgresql.org
Subject: Re: more 10K disks or less 15K disks
Date: Thu, 29 Apr 2010 10:31:50 -0700
Message-ID: <k2jf2fd819a1004291031m97580ei3d1ad5f486033222@mail.gmail.com> (raw)
In-Reply-To: <u2yf2fd819a1004291026z89cbd919m7d11c74f9b14a1eb@mail.gmail.com>
References: <i2pf2fd819a1004281127sf91d988cua1d95d13d09dae09@mail.gmail.com>
<4BD8DCEA.2020003@2ndquadrant.com>
<u2zf2fd819a1004282145wc60c3b39o7f0679fec9f607f8@mail.gmail.com>
<4BD9198E.904@2ndquadrant.com>
<u2yf2fd819a1004291026z89cbd919m7d11c74f9b14a1eb@mail.gmail.com>
I also want to add that with the perc 6i controllers..we have never
had issues. We have been running postgres nonstop for over 2 years and
sustaining a throughput of over 60-100 million messages a day without
breaking sweat. (postgres 8.1.9 on linux 32 bit )
I have to say I am impressed with the stability/performance of
postgres as well as the commodity hardware we use. We do have rare
disk failures..but the hot swappable drives make is easy to pop one in
and the RAID layer does the rebuilding very well.
On Thu, Apr 29, 2010 at 10:26 AM, Anj Adu <fotographs@gmail.com> wrote:
> All the disks are usually laid out in a single RAID 10 stripe . There
> are no dedicated disks for the OS/WAL as storage is a premium
>
> On Wed, Apr 28, 2010 at 10:30 PM, Greg Smith <greg@2ndquadrant.com> wrote:
>> Anj Adu wrote:
>>>
>>> We do not archive the WALs. We use application-level replication to
>>> achieve redundancy. WAL archiving was difficult to support with the
>>> earlier hardware we had ( 6x300G 10K disks Dell 2850) given the
>>> volumes we were dealing with. The RAID card should be from the same
>>> manufacturer (LSI in Dell's case).
>>>
>>
>> The database is generating WAL files that are written to the pg_xlog
>> directory. Sometimes this is broken out into a separate drive so that it's
>> possible to measure how much I/O is being written to there, as opposed to
>> the main database drive. That's the WAL writing I was asking about, not the
>> overhead of archiving WAL files to elsewhere. The way that WAL writes go to
>> disk, you can't always speed them up just by throwing more disks at
>> them--sometimes, you just need the individual disk involved to be as fast as
>> possible.
>>
>> You should try to get the same Dell RAID controller you're already using,
>> that you know delivers good performance running your app. All I've heard
>> about the models released after the Perc 6i has been bad news. Dell varies
>> how much they tinker with the LSI firmware in their own version of each
>> card, and they didn't do very much of that in the Perc 6 series. They seem
>> to be changing around the newer models more again, which is always bad news.
>>
>> --
>> Greg Smith 2ndQuadrant US Baltimore, MD
>> PostgreSQL Training, Services and Support
>> greg@2ndQuadrant.com www.2ndQuadrant.us
>>
>>
>
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To: pgsql-admin@postgresql.org
Cc: fotographs@gmail.com, greg@2ndquadrant.com
Subject: Re: more 10K disks or less 15K disks
In-Reply-To: <k2jf2fd819a1004291031m97580ei3d1ad5f486033222@mail.gmail.com>
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