[Gluster-users] iowait - ext4 + ssd journal

[Paul Robert Marino]

you are partially correct.
the -i and -L options have not been implemented in xfs_grow.
that said
1) The journal size will increase automatically to the appropriate
size based data area size in the  its just you cant manually specify
the size.

2) While it is true you cant switch between internal and external
journals directly you can do it with xfs_dump and xfs_restore.
    Honestly most people would be scared to do that with ext4 on a
production filesystem as well.






On Thu, Nov 6, 2014 at 7:33 AM, Lindsay Mathieson
<lindsay.mathieson at gmail.com> wrote:
> 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."
>
>
>
> --
>
> Lindsay
>
>
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