Erik Mouw wrote:
On Fri, Feb 10, 2006 at 10:01:09AM +0100, Mirko Benz wrote:
Does a high speed NVRAM device makes sense for Linux SW RAID? E.g. a PCI
card that exports battery backed memory.
Unless it's very large (i.e.: as large as one of your disks), it
doesn't make sense. It will probably break less often, but it doesn't
help you in case a disk really breaks. It also won't speed up an MD
device much.
Could that significantly improve write speed for RAID 5/6 (e.g. via an
external journal, asynchronous operation and write caching)?
You could use it for an external journal, or you could use it as a swap
device.
Let me concur, I used external journal on SSD a decade ago with jfs
(AIX). If you do a lot of operations which generate journal entries,
file create, delete, etc, then it will double your performance in some
cases. Otherwise it really doesn't help much, use as a swap device might
be more helpful depending on your config.
What changes would be required?
None, ext3 supports external journals. Look for the -O option in the
mke2fs manual page. Using the NVRAM device as swap is not different
from a using "normal" swap partition.
Erik
--
bill davidsen <davidsen@xxxxxxx>
CTO TMR Associates, Inc
Doing interesting things with small computers since 1979
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