[CentOS] ext4, 4k sector alignment
R P Herrold
herrold at owlriver.com
Mon Jul 25 17:23:39 UTC 2011
On Mon, 25 Jul 2011, Les Mikesell wrote:
> My questions for any filesystem experts are:
>
> Is there a way to adjust the existing md partitions to get the right
> alignment for 4k sectors without having to do a file-oriented copy to
> new partitions? A resize + a dd copy to shift the position might be
> feasible time-wise if that would work.
no expert here, but I have the scars across my back from
pulling arrows out, as a pioneer
We have hit the issue on our storage backend which runs ext4,
and on some of our dom0 built before the 4k sector alignment
was generally acknowledged and known to be potentially in play
We have some non-conformant units, and after seaching,
concluded that a 'wipe and rebuild' was the most time
efficient process for us -- YMMV
> Is it worth converting to ext4?
ext4 is pleasant in some large filesystem cases, but probably
overkill as a blanket option.
Certainly it is 'wayy overkill for domU as a general rule, as
it makes for a more fragile image in the sense that generic
tools are less likely to work without higher version and skill
levels when a filesystem gets horked up and a repair
expedition has to be mounted ... we had an issue that a
'dirty' filesystem that would not fsck kept showing up in a
nightly backup exception report, and ended up manually
repairing what should have been able to be repaired
automatically
> Is there a difference between doing this on 5.6 or 6.x?
in C5, it took extra effort to use the technology preview; in
C6 it is natively available
> If I start over from scratch with 6.x, will the partitioning tools
> automatically align for 4k sector drives (with/without lvm?)?
no idea if gparted does this by default -- it does not in all
versions; certainly fdisk did not -- 4k alignment is on our
deployment checklist, and we are manually checking
partitioning to make sure, when we are rebuilding boxes
-- Russ herrold
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