[Gluster-users] iowait - ext4 + ssd journal

Lindsay Mathieson lindsay.mathieson at gmail.com
Thu Nov 6 12:33:08 UTC 2014

On Tue, 4 Nov 2014 11:58:01 AM you wrote:
> Actually, it can.  I remember playing with it *way* back in the day when 
> XFS was first ported to Linux.  From 'man mkfs.xfs':
>         The  metadata  log can be placed on another device to reduce the
> number of disk seeks.  To create a filesystem on the
> first  partition  on  the first  SCSI  disk with a 10000 block log located
> on the first partition on the second SCSI disk, use:
>                mkfs.xfs -l logdev=/dev/sdb1,size=10000b /dev/sda1

Couple of concerns re this:

- the journal can only be mounted via device name, no guid or volume name. If the 
device name order changes your disk won't mount.

- from this page:http://www.raid6.com.au/posts/fs_ext4_external_journal/

"/xfs can not be mounted if external journal device is lost neither it can be reconfigured 
to *convert journal back to local* or to change its size./"

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