On 07/08/2017 02:34 AM, Brad Campbell wrote:
On 08/07/17 08:41, Ram Ramesh wrote:
Hi,
I asked in other linux forums and did not get enough info. So I come
here even though this is not mdadm/RAID issue.
I replaced 3TB disks in my 6-disk RAID6 with 6TB and now my md0 is 24TB.
I had 32bit version of ext4 on it which can only be grown to 16TB. Any
one had this issue before and any _/inplace/_ good solution to grow ext4
to full 24TB? It is unlikely that I will be able to back up and recreate
file system.
Ignore this first suggestion if you are absolutely reliant on data
integrity and don't have backups of any critical data.
Take 2 of the 6TB drives, create a 12TB RAID0 or Linear and copy all
your data to that.
Create the 6 drive RAID6 with 2 disks missing, copy all the data back,
then add the disks you used in the first copy back to the array.
I had this issue a few years ago and decided buying some extra disks
to use as scratch was a better move for me. In your shoes I would have
found 6 extra SATA ports on a machine (any machine), created the new
filesystem and rsynced the data across, then swapped the disks into
the production machine.
In fact I've just done that migrating from 14x2TB drives to 8x6TB
drives, but I keep a staging machine around for testing that has 15
drive bays for just this sort of migration.
This is the 4th time I've done it in 13 years. 15x250GB -> 8x1TB ->
14x2TB -> 8x6TB. The advantage is you never lose data integrity or
redundancy, and you can keep the old drives around in a box until you
are sure the new build is reliable.
Alternatively, find a machine with 6 slots, build a RAID6 from the
drives you already have. Copy the data across, re-format the new array
and copy the data back. A bit of double handling, but no loss of
redundancy or integrity. Run md5 or something over all the files to
make sure it's all good, or use rsync with the "always checksum"
option, although this is slow.
Brad
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Thanks for the details. I think I have 2x4TB and 2x3TB spares. This is
enough for the data I have and I have scripted a way to distribute files
across those to make a mock backup/snapshot. They are old drives and I
do not trust their shelf life. So, I consider that there is no backup.
However, for short/week exercise, it may be considered as a safe data.
So, I am not that paranoid about doing inplace changes. I just don't
like to choose known risky paths - a more tested approach is preferred
even if it has nonzero propability of failure. That is all.
Ramesh
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