From: David Brown <david@westcontrol.com>
To: stan@hardwarefreak.com
Cc: David Brown <david.brown@hesbynett.no>, linux-raid@vger.kernel.org
Subject: Re: RAID5 created by 8 disks works with xfs
Date: Mon, 02 Apr 2012 09:04:10 +0200 [thread overview]
Message-ID: <4F794F6A.1010808@westcontrol.com> (raw)
In-Reply-To: <4F793C6E.1080000@hardwarefreak.com>
On 02/04/2012 07:43, Stan Hoeppner wrote:
> On 4/1/2012 5:33 AM, David Brown wrote:
>
>> For an application like this, it would probably make sense to put the
>> xfs log (and the mdraid bitmap file, if you are using one) on a separate
>> disk - perhaps a small SSD.
>
> XFS only journals metadata changes. Thus an external journal is not
> needed here as there is no metadata in the workload.
>
Won't there still be metadata changes as each file is closed and a new
one started, or as more space is allocated to the files being written (I
know xfs has delayed allocation and other tricks to minimise this, but
it can't be eliminated entirely). Each time the metadata or log needs
written, you'll get a big discontinuity in the writing as the disks
heads need to jump around (especially for RAID5!).
It would make sense to have a separate disk (again, SSD is logical) for
the OS and other files anyway, keeping the big array for the data.
Putting the xfs log there too would surely be a small but helpful step?
next prev parent reply other threads:[~2012-04-02 7:04 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-03-31 1:22 RAID5 created by 8 disks works with xfs daobang wang
2012-03-31 7:59 ` Mathias Burén
2012-03-31 20:09 ` Stan Hoeppner
2012-04-01 1:16 ` daobang wang
2012-04-01 2:05 ` daobang wang
2012-04-01 5:13 ` Stan Hoeppner
2012-04-01 3:51 ` Stan Hoeppner
2012-04-01 5:12 ` daobang wang
2012-04-01 5:40 ` Stan Hoeppner
2012-04-01 5:59 ` daobang wang
2012-04-01 6:20 ` daobang wang
2012-04-01 7:08 ` Marcus Sorensen
2012-04-02 3:47 ` Stan Hoeppner
2012-04-05 0:48 ` daobang wang
[not found] ` <CACwgYDOtCoVF-p+KKqPYxHhA4vWF78Ueecx9hcVWLoyxFWzV9Q@mail.gmail.com>
2012-04-05 21:01 ` Stan Hoeppner
2012-04-06 0:25 ` daobang wang
2012-04-06 2:33 ` daobang wang
2012-04-06 6:00 ` Jack Wang
2012-04-06 6:45 ` daobang wang
2012-04-06 6:49 ` daobang wang
2012-04-06 8:18 ` Stan Hoeppner
2012-04-06 8:45 ` daobang wang
2012-04-06 11:12 ` Stan Hoeppner
2012-04-18 2:23 ` daobang wang
2012-04-02 3:12 ` Stan Hoeppner
2012-04-01 10:33 ` David Brown
2012-04-01 12:28 ` John Robinson
2012-04-02 6:59 ` David Brown
[not found] ` <CA+res+QkLi7sxZrD-XOcbR47CeJ5gADf7P6pa1w1oMf8CKSB4g@mail.gmail.com>
2012-04-02 8:01 ` John Robinson
2012-04-02 10:01 ` Jack Wang
2012-04-02 10:28 ` John Robinson
2012-04-02 20:41 ` Stan Hoeppner
2012-04-02 5:43 ` Stan Hoeppner
2012-04-02 7:04 ` David Brown [this message]
2012-04-02 20:21 ` Stan Hoeppner
2012-04-01 4:52 ` Stan Hoeppner
2012-04-01 8:06 ` John Robinson
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