On 25 Mar 2005, at 13:00, John Coleman wrote:
> With whichever card I buy, I'm going to be putting 3x 400Gig drives in
> them as one raid5 array, single logical drive, formatted with XFS. I
> intend to expand this array with more drives down the road but I have
> a query regarding the array expansion; after plugging in the new
> drive, I expect the controller to intergrate the drive into the
> current array, and that the existing logical drive will need to be
> increased to take advantage of the new space offered.
> I have 2 concerns regarding this:
> Firstly, ignoring downtime, will the existing partition on the logical
> drive remain untouched, with the additional space showing up as
> unpartitioned dirive space?
> Secondly, I have never had to change the size of a partition where the
> data was critical, I assume there are methods in place to expand the
> existing partition to use the whole logical drive, and that XFS
> supports expansion in such a way?
XFS does indeed support expanding a filesystem, with the xfs_growfs
command. The xfs expansion will be the least of your problems. You need
to do the following:
1) Add the extra disk into the RAID-5 array.
2) Increase the size of the partition on which the filesystem lives.
3) Extend the filesystem.
Getting the easy stuff out of the way first, 3) is supported by
xfs_growfs.
2) is a bit of a mess, because you have a disk which has a partition
table, and suddenly that partition table is wrong and needs changing.
I've done this on raw disks, and it has worked, and it has failed. LVM
may be of some help here - a little light reading might be in order :-)
1) is where Aughrim may be lost. IIRC we had this discussion here a
while ago. With any RAID cards I have used, adding an extra drive into
the array means rebuilding the array (because data is striped across
all disks). However, I'm pretty sure that somebody on the list
mentioned some cards which have some magic means of doing just this. A
search of the archives might help (I tried, but my google foo is weak).
Last but not least - you mentioned critical data. It'd take a much
braver man than me to try to do this with valuable data which is not
safely backed up.
Niall
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