Re: RAID5 reconfig

Re: RAID5 reconfig

[Marco Shaw]

On Fri, 2002-12-27 at 21:25, TJ wrote:
> Do the current raidtools allow enlarging a RAID 5 array by adding more disks
> to it without initializing a new
> array? This feature is found in some hardware raid controllers.

Use with extreme care:
http://unthought.net/raidreconf/index.shtml

Someone posted a success story on this list a few weeks ago using a
pretty big RAID5 volume/array.

Marco

PS: Please use the 'Subject' field.

Re: RAID5 reconfig

[TJ]

> Use with extreme care:
> http://unthought.net/raidreconf/index.shtml

> Someone posted a success story on this list a few weeks ago using a
> pretty big RAID5 volume/array.

> Marco

> PS: Please use the 'Subject' field.

Sorry about that.. Please CC me, I don't seem to be getting any feed from
the list.

Thanks for the link. I've been reading up on others experiences and
documentation seems somewhat thin. Does a mini-HOWTO exist anywhere?
From what I've read, first raidreconf is used to change the array, then
fsck -f is run to check the product, then the file system resize utility
must be used to change the size of the filesystem on the RAID array. Then it
would probably be a good idea to run fsck -f once more. This should be
sufficient to add more disks to a RAID 5 array and enlarge the filesystem to
take advantage of the larger block device. Am I missing anything?

Re: RAID5 reconfig

[Jakob Oestergaard]

On Sat, Dec 28, 2002 at 11:43:25AM -0500, TJ wrote:
> > Use with extreme care:
> > http://unthought.net/raidreconf/index.shtml
> 
> > Someone posted a success story on this list a few weeks ago using a
> > pretty big RAID5 volume/array.
> 
> > Marco
> 
> > PS: Please use the 'Subject' field.
> 
> Sorry about that.. Please CC me, I don't seem to be getting any feed from
> the list.
> 
> Thanks for the link. I've been reading up on others experiences and
> documentation seems somewhat thin. Does a mini-HOWTO exist anywhere?
> >From what I've read, first raidreconf is used to change the array, then
> fsck -f is run to check the product, then the file system resize utility
> must be used to change the size of the filesystem on the RAID array. Then it
> would probably be a good idea to run fsck -f once more. This should be
> sufficient to add more disks to a RAID 5 array and enlarge the filesystem to
> take advantage of the larger block device. Am I missing anything?

Only that in some scenarios raidreconf fails horribly - this seems to at
least happen if you have hot spares configured.

Make sure you have a good backup.  Please report success/failure to the
list - that is greatly appreciated  :)

-- 
................................................................
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:.........................: putrid forms of man                :
:   Jakob Østergaard      : See him rise and claim the earth,  :
:        OZ9ABN           : his downfall is at hand.           :
:.........................:............{Konkhra}...............:
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Re: RAID5 reconfig

[TJ]

Well, raidreconfig worked wonderfully for me, however I screwed up
afterwards. I fscked before resize2fs, but forgot to do it again afterwards
and mounted the filesystem and used it. That caused it enough damage that I
damaged it and rebuilt it from backups. Raidreconfig worked excellently. It
handled unequal partition sizes just fine, though running it with the --test
flag returned an error that one partition was too small (0kb).

One feature request:

Go from 4 40gb disks in RAID 5 to 3 80gb devices in RAID 5: 1 80 gb disk and
the 4 40gb drives in RAID 0.


Old raidtab:

raiddev                        /dev/md0
raid-level                     0
nr-raid-disks                2
chunk-size                    64k
persistent-superblock   1
nr-spare-disks              0
    device                      /dev/hda4
    raid-disk                  0
    device                      /dev/hdc1
    raid-disk                 1

New raidtab:

raiddev                        /dev/md0
raid-level                      5
nr-raid-disks                4
chunk-size                   128k
persistent-superblock       1
parity-algorithm            left-symmetric
nr-spare-disks              0
    device          /dev/hda4
    raid-disk     0
    device          /dev/hdb1
    raid-disk     1
    device          /dev/hdc1
    raid-disk     2
    device          /dev/hdd1
    raid-disk     3

Re: RAID5 reconfig

[Scott McDermott]

TJ on Sun 19/01 22:16 -0500:
> I fscked before resize2fs, but forgot to do it again afterwards and
> mounted the filesystem and used it.

You should not have to.  I have never used e2fsck after resize2fs and
have never had a problem with perhaps a couple dozen resizes.