On 05/07/2013 09:53 AM, Robin Hill wrote:
On Fri May 03, 2013 at 06:28:02PM +0200, Roberto Nunnari wrote:
Robin Hill wrote:
The safest option would be:
- add in the new disks
- partition to at least the same size as your existing partitions (they
can be larger)
- add the new partitions into the arrays (they'll go in as spares)
- grow the arrays to 4 members (this avoids any loss of redundancy)
- wait for the resync to complete
- install grub/lilo/syslinux to the new disks
- fail and remove the old disk partitions from the arrays
- shrink the arrays back down to 2 members
- remove the old disks
Then, if you're keeping the same number of partitions but increasing the
size:
Ok.. got here.
- grow the arrays to fill the partitions
- grow the filesystems to fill the arrays
Now the scary part.. so.. here I believe I should give the following
commands:
mdadm --grow /dev/md0 --size=max
mdadm --grow /dev/md1 --size=max
mdadm --grow /dev/md2 --size=max
Yep, that's right. Make sure they've actually grown to the correct size
before you progress though - I have had one occasion where using
--size=max actually ended up shrinking the array and I had to manually
work out the size to use in order to recover. That was using an older
version of mdadm though, and I've not seen it happen since.
and after that
fsck /dev/md0
fsck /dev/md1
fsck /dev/md2
You'll need 'fsck -f' here to force it to run.
and
resize2fs /dev/md0
resize2fs /dev/md1
resize2fs /dev/md2
Correct?
That should be it, yes.
.. I still have a couple of questions:
1) how do I know if there's a bitmap?
Check /proc/mdstat - it'll report a bitmap - e.g.
md6 : active raid6 sdg[0] sdf[6] sde[5] sdi[2] sdh[1]
11721052272 blocks super 1.2 level 6, 16k chunk, algorithm 2 [5/5] [UUUUU]
bitmap: 0/30 pages [0KB], 65536KB chunk
2) at present /dev/md2 usage is 100%.. could that cause any problem?
It'll slow things down a bit but otherwise shouldn't be an issue.
3) the new drives are 2TG drives.. As around one year ago had trouble on
linux (it was a server dated 2006 with CentOS 5) that would not handle
drives larger than 2TB.. I wander what happens if one day one drive
fails and the drive I'll buy to replace will be sold as 2TB but in
reality slightly larger than 2TB.. what will happen? Will linux fail
again to use a drive larger than 2TB?
All 2TB drives are exactly the same size. Since somewhere around the
320G/500G mark, all drive manufacturers have agreed to standardise the
drive sizes, so getting mismatches like this is a thing of the past.
At present I'm on ubuntu 10.04, all software from standard distribution.
Pitfalls I should know?
You'll need to use GPT partitions instead of standard MBR partitions for
drives over 2TB, but there shouldn't be any issue with handling them.
Cheers,
Robin
Thank you Robin.
Today I'm on holiday, but I will look at it tomorrow. :-)
Best regards.
Robi
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