UFS journal size

Ivan Voras ivoras at freebsd.org
Wed Sep 21 16:01:28 UTC 2011

On 21/09/2011 11:48, Ross wrote:
> Quoting the manpage:
>          -s jsize  Specifies size of the journal if only one provider is
>                        used for both data and journal.  The default is one
>                        gigabyte.  Size should be chosen based on provider's
>                        load, and not on its size; recommended minimum is twice
>                        the size of the physical memory installed.  It is not
>                        recommended to use gjournal for small file systems
>                        (e.g.: only few gigabytes big).
> My question is: if I have 4 or 8 GB of RAM should I create 8 or even
> 16 GB journals?.. This seems huge especially if the fs size without
> journal is only 10 gigs. Or the recommended minimum is for systems low
> on RAM?

You are probably missing that gjournal does full data journaling, not
just metadata as is more common with other systems, so you need a
journal which can hold *at least* everything you can hold in RAM, and
then twice as much since one half may be replaying while other is being
filled up. Even this is an estimate since it's heavily load-dependant.

Or you can wait for 9.0 with metadata journaling.

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