last year I set up a Software-RAID5 with 5x3TB yielding 12TB of usable capacity. Just today, needing more storage, I have finished growing the RAID to two more 3TB disks:
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid5 sdd1[7] sde1[6] sdb1[4] sda1[5] sdc1[2] sdg1[1] sdf1[0]
17580801024 blocks super 1.2 level 5, 512k chunk, algorithm 2 [7/7] [UUUUUUU]
unused devices: <none>
This means that I should now have approximately 6x3TB = 18TB available on /dev/md0
. resize2fs
, called without a size parameter, now told me that the new size is not possible in 32 bit mode. Some research showed that this is a common problem and not easily solvable without heavy tinkering which I am not willing to do.
tune2fs
confirmed that the 64bit
-flag was indeed missing :-( although in the config files auto_64-bit_support = 1
is set (and should also have been set when the filesystem was created). But there is no use in whining about something I can't change afterwards.
Sadly, full backup and restore is not an option (I know, there should exist a backup of all the data but there is only enough money to backup the really important part of it).
I then tried to resize the filesystem to 16TB with resize2fs -S 128 /dev/md0 16T
which seemed to work but came back with an error telling me that there is not enough space on the device and advising me to run e2fsck -fy /dev/md0
- strange thing. My heart pounded like crazy until that check came back okay! Telling it to resize to 15T
worked, though.
I think we can live with around 15TB for some more months but having approximately 3TB hanging around with no use is something I really don't like. My question now is, how I can put these 3TB to use. My directions of research were
- Converting to btrfs, which seems to support filesystems larger than 16TB and is possible without a backup/restore cycle - but different sources say that this is not reliable and should not be used in production.
- Partitioning
/dev/md0
to create a second filesystem on the remaining 3TB - seems to be impossible (partition table typeloop
) - Setting up LVM - is this even possible without reformatting?
but none of these "solutions" were sufficiently well documented/tested or were not an option as stated above so I am now stuck with a /dev/md0
of 18TB containing an ext4 filesystem with only 15TB and 3TB of free space. Does anybody have an idea what else I could try/do/consider?