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Re: Raid 10 chunksize

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From:	david@lang.hm
Subject:	Re: Raid 10 chunksize
Date:	April 1, 2009 , 20:38:46
Msg-id:	alpine.DEB.1.10.0904011337310.28893@asgard.lang.hm (view: Whole thread, Raw)
In response to:	Re: Raid 10 chunksize (Mark Kirkwood)
Responses:	Re: Raid 10 chunksize ()
List:	pgsql-performance

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Raid 10 chunksize (Mark Kirkwood, 25 March 2009, 01:25:46 )
Re: Raid 10 chunksize (Scott Carey, 25 March 2009, 01:48:46 )
Re: Raid 10 chunksize (David Rees, 25 March 2009, 02:04:49 )
Re: Raid 10 chunksize (Greg Smith, 25 March 2009, 03:30:19 )
Re: Raid 10 chunksize (Scott Marlowe, 25 March 2009, 02:11:22 )
Re: Raid 10 chunksize (Mark Kirkwood, 25 March 2009, 03:51:42 )
Re: Raid 10 chunksize (Jerry Champlin, 25 March 2009, 10:47:43 )
Re: Raid 10 chunksize (Mark Kirkwood, 26 March 2009, 06:12:23 )
Re: Raid 10 chunksize (Scott Carey, 26 March 2009, 21:49:10 )
Re: Raid 10 chunksize (Mark Kirkwood, 01 April 2009, 08:27:02 )
Re: Raid 10 chunksize (Mark Kirkwood, 03 April 2009, 08:54:19 )
Re: Raid 10 chunksize (Greg Smith, 25 March 2009, 08:08:05 )
Re: Raid 10 chunksize (Scott Carey, 25 March 2009, 16:16:44 )
Re: Raid 10 chunksize (Merlin Moncure, 02 April 2009, 17:58:48 )
Re: Raid 10 chunksize (Scott Carey, 02 April 2009, 20:20:26 )
Re: Raid 10 chunksize (Merlin Moncure, 02 April 2009, 20:27:11 )
Re: Raid 10 chunksize (Scott Carey, 02 April 2009, 20:44:28 )
Re: Raid 10 chunksize (Mark Kirkwood, 26 March 2009, 04:37:17 )
Re: Raid 10 chunksize (Greg Smith, 26 March 2009, 17:39:28 )
Re: Raid 10 chunksize (Mark Kirkwood, 02 April 2009, 06:31:28 )
Re: Raid 10 chunksize (Stef Telford, 26 March 2009, 00:58:19 )
Re: Raid 10 chunksize (Mark Kirkwood, 26 March 2009, 05:45:40 )
Re: Raid 10 chunksize (Scott Carey, 26 March 2009, 21:45:16 )
Re: Raid 10 chunksize (Scott Carey, 26 March 2009, 22:02:15 )
Re: Raid 10 chunksize (Mark Kirkwood, 01 April 2009, 08:13:11 )
Re: Raid 10 chunksize (Stef Telford, 01 April 2009, 14:46:27 )
Re: Raid 10 chunksize (Greg Smith, 01 April 2009, 16:08:23 )
Re: Raid 10 chunksize (Stef Telford, 01 April 2009, 16:15:47 )
Re: Raid 10 chunksize (Scott Marlowe, 01 April 2009, 16:41:51 )
Re: Raid 10 chunksize (Stef Telford, 01 April 2009, 16:49:03 )
Re: Raid 10 chunksize (Scott Marlowe, 01 April 2009, 16:55:18 )
Re: Raid 10 chunksize (Greg Smith, 01 April 2009, 17:49:53 )
Re: Raid 10 chunksize (Matthew Wakeling, 01 April 2009, 17:54:10 )
Re: Raid 10 chunksize (Scott Marlowe, 01 April 2009, 17:58:58 )
Re: Raid 10 chunksize (Scott Carey, 01 April 2009, 22:15:44 )
Re: Raid 10 chunksize (, 01 April 2009, 22:59:30 )
Re: Raid 10 chunksize (Scott Marlowe, 01 April 2009, 23:39:34 )
Re: Raid 10 chunksize (Matthew Wakeling, 01 April 2009, 17:01:23 )
Re: Raid 10 chunksize (Scott Marlowe, 01 April 2009, 17:04:17 )
Re: Raid 10 chunksize (Stef Telford, 01 April 2009, 17:17:34 )
Re: Raid 10 chunksize (Scott Carey, 01 April 2009, 22:14:42 )
Re: Raid 10 chunksize (Matthew Wakeling, 01 April 2009, 16:51:31 )
Re: Raid 10 chunksize (Scott Carey, 01 April 2009, 22:17:48 )
Re: Raid 10 chunksize (Greg Smith, 02 April 2009, 08:53:31 )
Re: Raid 10 chunksize (James Mansion, 02 April 2009, 19:25:34 )
Re: Raid 10 chunksize (Greg Smith, 03 April 2009, 09:53:38 )
Re: Raid 10 chunksize (Scott Carey, 02 April 2009, 20:34:20 )
Re: Raid 10 chunksize (Greg Smith, 03 April 2009, 10:30:21 )
Re: Raid 10 chunksize (Ron Mayer, 03 April 2009, 00:17:03 )
Re: Raid 10 chunksize (Hannes Dorbath, 03 April 2009, 08:24:00 )
Re: Raid 10 chunksize (Stef Telford, 01 April 2009, 19:51:53 )
Re: Raid 10 chunksize (Stef Telford, 01 April 2009, 20:44:24 )
Re: Raid 10 chunksize (Scott Carey, 01 April 2009, 22:36:24 )
Re: Raid 10 chunksize (Mark Kirkwood, 02 April 2009, 06:19:35 )
Re: Raid 10 chunksize (, 01 April 2009, 20:38:46 )
Re: Raid 10 chunksize (, 01 April 2009, 20:47:36 )
Re: Raid 10 chunksize (Greg Smith, 03 April 2009, 09:29:15 )
Re: Raid 10 chunksize (, 04 April 2009, 01:05:32 )
Re: Raid 10 chunksize (Greg Smith, 04 April 2009, 02:26:56 )
Re: Raid 10 chunksize (Scott Carey, 04 April 2009, 05:25:08 )

On Wed, 1 Apr 2009, Mark Kirkwood wrote:

> Scott Carey wrote:
>>
>> A little extra info here >>  md, LVM, and some other tools do not allow the
>> file system to use write barriers properly.... So those are on the bad list
>> for data integrity with SAS or SATA write caches without battery back-up.
>> However, this is NOT an issue on the postgres data partition.  Data fsync
>> still works fine, its the file system journal that might have out-of-order
>> writes.  For xlogs, write barriers are not important, only fsync() not
>> lying.
>>
>> As an additional note, ext4 uses checksums per block in the journal, so it
>> is resistant to out of order writes causing trouble.  The test compared to
>> here was on ext4, and most likely the speed increase is partly due to that.
>>
>>
>
> [Looks at  Stef's  config - 2x 7200 rpm SATA RAID 0]  I'm still highly
> suspicious of such a system being capable of outperforming one with the same
> number of (effective) - much faster - disks *plus* a dedicated WAL disk
> pair... unless it is being a little loose about fsync! I'm happy to believe
> ext4 is better than ext3 - but not that much!

given how _horrible_ ext3 is with fsync, I can belive it more easily with
fsync turned on than with it off.

David Lang

> However, its great to have so many different results to compare against!
>
> Cheers
>
> Mark
>
>
>

pgsql-performance by date:

From: Scott Marlowe
Date: 01 April 2009, 17:39:34
Subject: Re: Raid 10 chunksize

From: Mark Kirkwood
Date: 02 April 2009, 00:19:35
Subject: Re: Raid 10 chunksize