[tech] Backups

[David Adam]

As probably my last action as a Wheel member, I've sorted out something 
about the backup server that's been bugging me for ages.

At present it has an SSD wedged in as a boot drive, and four 2 TB 
drives (WD Red, 2 x WD Black, Hitachi Deskstar). Until just now, three of 
these drives were in hardware RAID-5 with LVM and ext4 on top. The fourth 
is in a RAID-0 (single disk) with ZFS on top.

I thought that the array could not be expanded without wiping it, and we 
only had three drives initially. I put ZFS on the new drive to get 
something out of compression, though we were only getting a compression 
ratio of 1.01, so it's hardly worth it.

However, I discovered the PERC 5/i in the machine *can* resize the RAID - 
online, even! - and it is currently doing so using this awful series of 
commands:

Delete the old single-disk array, virtual disk 1 on adapter 0 with:
# megacli -CfgLdDel -L1 -a0
Start a reconfiguration operation on a RAID-5 array adding the new disk 
(disk numbers from the incredibly useful megaclisas-status tool) to 
virtual disk 0 on adapter 0:
# megacli -LDRecon -Start -r5 -Add -PhysDrv '[8:2]' -L0 -a0
Watch paint dry^W^W the array rebuild with:
# megacli -LDRecon -ProgDsply -L0 -a0

This is likely to take some hours so I have disabled the backups for now 
by commenting them out in the "backups" user crontab.

Mollitz itself is not backed up (except locally), so /backups/conf 
probably needs putting into git or similar.

Once it's done I will resize the partition, LVM volume and the filesystem.

David Adam
Soon-to-be-not UCC Wheel Member
zanchey@