Re: external journal questions

[Jeff Mahoney <jeffm@suse.com>]

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Jure Pečar wrote:
> Hi all,
> 
> Now that solid state disks are getting affordable (Gigabyte iRam, for
> example), it makes sense to use them as external journal with full data
> journaling, so they cache all the small writes and dump them to disks
> in one single sequential write on every journal flush.
> 
> I know how to configure that under ext3. Simply set up external journal
> and mount filesystem with data=journal and commit=600 or some such
> value. But I'm not so sure about reiserfs.
> 
> I know it now knows how to do full data journaling, but I can't find
> the docs anywhere that would mention commit mount option. Does it work
> at all and does it work in the same way as for ext3?
> 
> Also, I've seen patches by Jeff Mahoney from november last year that
> optimize some external journal defaults. I'm thinking about a 7Tb or so
> Coraid AoE device with 4gb iRam as external journal ... does anyone run
> something like this in production? How well does it work?
> 
> Jeff, are your pathces already in the Linus tree or do I have to use
> some -mm or Suse kernel?

Hi Jure -

The kernel patches have been part of mainline since Nov 30, 2005. Any
kernel newer than 2.6.15-rc4 will contain them.

You may also want to patch your reiserfsprogs with the patch I posted
along with the kernel patch. This just adjusts reiserfsprogs to use some
sane defaults. I've attached it for convenience.

- -Jeff

- --
Jeff Mahoney
SUSE Labs
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