Journal config for SAN array

Jure Pečar pegasus at
Sun Nov 23 16:34:01 UTC 2008

On Sun, 23 Nov 2008 07:06:28 -0800 (PST)
KenShelby <kshelby at> wrote:

> I'm not looking for a single "magic bullet" answer.  Are there any
> guidelines at all, any best practices that have been found over time to
> be a good place to start?  What I seek is either informed opinion or
> information - if it exists - about how to make choices on EXT3 journal
> configuration for a SAN installation.

Common sense and knowlege of your application are a good start.

You said that you have lots of random io, so I would be more concerned over
latency than bandwith. If your SAN provides you with good enough latency
then I wouldn't bother much about journal configs and go with defaults, but
if your SAN sits on something like iSCSI with noticeable latency then I'd
test a setup with journal on local disk, possibly even in full data
journaling mode. If I had the money I'd look into SSDs for that purpose,
either in form of SSD sata/sas drive or in form of PCIe card (fusion-io for


Jure Pečar

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