Date: Wed, 02 Aug 2006 14:06:11 +1200
From: Mark Kirkwood <markir@paradise.net.nz>
Subject: Re: XFS filessystem for Datawarehousing
In-reply-to: <012d01c6b5b4$6db33680$0a00a8c0@trivadis.com>
To: Milen Kulev <makulev@gmx.net>
Cc: pgsql-performance@postgresql.org
Message-id: <44D00893.4060804@paradise.net.nz>
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References: <012d01c6b5b4$6db33680$0a00a8c0@trivadis.com>

Milen Kulev wrote:

> Is anyone using XFS for storing/retrieving relatively large amount of data  (~ 200GB)?
> 

Yes, but not for that large - only about 40-50 GB of database data.

> If yes, what about the performance and stability of  XFS.

I'm pretty happy with the performance, particularly read (get 215MB/s 
sequential 8K reads from 4 (P)ATA drives setup as software RAID 0). I 
have always found XFS very stable (used it on servers for several years).

> I am especially interested in recommendations about XFS mount options and mkfs.xfs options.
> My setup will be roughly this:
> 1) 4  SCSI HDD , 128GB each, 
> 2) RAID 0 on the four SCSI HDD disks using LVM (software RAID)
> 

> 
> My questions:
> 1) Should I place external XFS journal on separate device ?
> 2) What  should be the journal buffer size (logbsize) ?
> 3)  How many journal buffers (logbufs) should I configure ?
> 4) How many allocations groups  (for mkfs.xfs) should I  configure
> 5)  Is it wortj settion noatime ?
> 6) What I/O scheduler(elevators) should I use (massive sequencial reads)
> 7) What is the ideal stripe unit and width (for a RAID device) ? 
> 
>

1-3) I have not done any experimentation with where to put the journal, 
or its buffer size / number of them (well worth doing I suspect tho).

4) I left it at the default.

5) I use noatime, but have not measured if there is any impact if I 
leave it off.

6) deadline scheduler seemed to give slightly better performance for 
sequential performance.

7) I tried out stripe width 2,4 (with 4 disks), and they seemed to give 
the same results. Stripe unit of 256K (tested 32K, 64K, 128K) seemed to 
give the best sequential performance. My software raid stripe size was 
matched to this in each case.


I'll be interested to hear what you discover :-)

Cheers

Mark