Ext3 users - Oct 2001 - using non-default blocks per group

I've been playing with the -g switch to mke2fs, which controls the blocks
per group.  This switch isn't documented.  I've been using it to balance
metadata traffic on RAID 0.

This seems to work fine in ext2.  Will I have any problems with ext3 where
the blocks per group is not a power of 2?

-jwb

On Oct 19, 2001  12:52 -0700, Jeffrey W. Baker wrote:
> I've been playing with the -g switch to mke2fs, which controls the
blocks
> per group.  This switch isn't documented.  I've been using it to
balance
> metadata traffic on RAID 0.
> 
> This seems to work fine in ext2.  Will I have any problems with ext3 where
> the blocks per group is not a power of 2?
This shouldn't cause any problems anywhere.  It may be that some poorly
coded ext2 tools will use "blocksize*8" as the number of blocks per
group,
but that is just plain wrong (even if it matches 99.9% of the configs out
there).  Ext3 does nothing (AFAIK) to change the behaviour of this part
of the code.

You do know about the "-R stride" option for mke2fs?  It is also
supposed
to help balance bitmap I/O across multiple disks.  It doesn't help with
inode tables, however, but since they are normally quite large, they should
be striped across multiple disks anyways.

Cheers, Andreas
--
Andreas Dilger  \ "If a man ate a pound of pasta and a pound of antipasto,
                 \  would they cancel out, leaving him still hungry?"
http://www-mddsp.enel.ucalgary.ca/People/adilger/               -- Dogbert

Hi,

On Fri, Oct 19, 2001 at 12:52:19PM -0700, Jeffrey W. Baker
wrote:
> I've been playing with the -g switch to mke2fs, which controls the
blocks
> per group.  This switch isn't documented.  I've been using it to
balance
> metadata traffic on RAID 0.
> 
> This seems to work fine in ext2.  Will I have any problems with ext3 where
> the blocks per group is not a power of 2?
No, although one important piece of metadata --- the journal --- will
not get balanced in respect of the -g setting in ext3's case.

Cheers,
 Stephen