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Re: [Sheflug] Ext3 Journal size



On Thu, 2002-05-23 at 16:45, José Luis Gómez Dans wrote:
>     Unfortunately, I deleted Alex Hundson's clarification of how
> tunefs deals with mounted/unmounted filesystems

That'll teach you :-P

> One things which didn't occur to me at the time was the size
> of the Journal (which in my case is in /.journal, and has a size of
> around 4 Megs). Is there an optimal size, or should the smallest size
> be used (1024 FS blocks)?

You -J'd it? Why?

Anyway, as usual, there isn't really an answer. What type of journaling
are you using? If you've got up-to-date tools, you'll probably have
ordered journally (the default), unless you changed it ;) Since you're
only really ordering data to disk and cacheing meta-ops, the size of
your journal isn't hugely critical. The journal entries last at most
about 5 sec, IIRC, so you need to make sure that the amount of meta-data
you're generating is less than 0.75Mb sec-1, otherwise you explode your
journal before the kernel comes to write stuff to disk again. With full
journalling, that may be a problem, but only really means that the
journal is getting flushed more often that usual - I'm not sure what
type of performance problem you would encounter with that.

FYI:

rendevous:/home/hudson_a# ls -lh /.journal 
-rw-------    1 root     root          32M Mar 29 19:09 /.journal
rendevous:/home/hudson_a# df -H | head -n 2
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda2             3.9G  2.5G  1.2G  66% /

4G/32M =~ 4 Meg per Gig of space. 

:)  

Cheers,

Alex.

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