[DRBD-user] Resizing Issues
Lee at titaninternet.co.uk
Fri Jun 13 21:49:23 CEST 2008
> You can only change the partition table and make the kernel see what
> happened when the device is not opened for I/O access. So
> failing over/ disabling the drbd servce before you try to resize the
> partition is the way to go. There is no way I know of to avoid this.
Further testing today reinforces this. We also tried resizing the underlying RAID array, but again, the extra size was not seen until processes were restarted.
> You then have to bear with the disadvantages of traditional
> partition schemes. This includes the lock of partition tables if
> anything is mounted. You should see to other Software for backup
> purposes. Try LRS:
Today we tried both Acronis and R1Soft CDP.
Acronis : simply didn't work. Backups of the logical volumes had no file contents, although they did create at roughly the expected size for the data. I expect its some incompatibility between Acronis and the drbd device.
CDP : worked fine for backing up /dev/drbdx and then restoring individual files, even if performance wasn't great. However attempting to do "volume" based restores to /dev/drbd causes the box to hang - I *was* able to backup /dev/drbd0 and restore it to /dev/sdb2 provided drbd wasn't running. I assume then its just a case of recreating metadata (external) and resyncing to your other node.
I would appreciate any advice from those with experience with large systems. We are building a mail cluster which will end up housing many terabytes of data. We ideally need a backup solution suitable for DR (bare metal) as well as the ability to restore an individual users mailbox quickly and easily. Oh and being able to grow the data LUNs easily too - we don't ask for much ;)
I didn't try that LRS tool you mentioned since it doesn't seem to take block level image backups. That's what we'll need for performance.
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