That's an excellent idea, I was going to add another disk for extra space right after migrating to raid6. Just to be clear, I'll be running the normalize attribute just once to straighten the array out right? Or will I have to do it for every extra drive I add in the future? And what are the N+1 you mention in --raid-devices=N+1 Thanks. 2012/5/6 NeilBrown <neilb@xxxxxxx> > > On Sun, 6 May 2012 10:17:52 +0000 Garðar Arnarsson <gardar@xxxxxxxxxxx> wrote: > > > My raid5 array has gotten a bit big, it's containing total 10 drives > > right now (I started out with 3 drives). So I am going to convert it > > to raid6 before it gets any bigger. > > > > I am doing a test-run on a virtual machine with virtual drives to see > > that everything works flawlessly. > > > > When I tried to convert the array to raid6 I got a error message about > > a missing backup-file > > > > mdadm --grow /dev/md0 --raid-devices=5 --level=6 > > > > mdadm level of /dev/md0 changed to raid6 > > mdadm: /dev/md0: Cannot grow - need backup-file > > mdadm: aborting level change > > > > I added the backup file and was able to convert the array successfully > > after that. > > > > My question is, how big is this backup file going to be? My real raid > > array consists of 2tb drives, will the backup file be as big as one > > drive in the array, or will it just be few megabytes or gigabytes? > > I'm asking because I'm wondering if I need to buy an extra hdd for the > > backup file or if the backup file can just be on my OS hdd that has > > around 100gb free. > > The backup file is a few megabytes. Around 16MB I think. > > However if you are likely to add another device in the not too distant future > you can save yourself a bit of time. > > If you > > mdadm --grow /dev/md0 --level=6 --layout=preserve > > It will just make the new few a 'Q-block' device, containing the extra RAID6 > 'parity' block for each stripe. This doesn't require any reshape or or any > backup file and is a lot faster. All it requires is a normal recovery > operation. > > Then when you later add another device you can > > mdadm --grow /dev/md0 --raid-devices=N+1 --layout=normalise > > This will convert from the Q-on-the-last-device layout to a more normal > rotated-P-and-Q layout at the same time as adding extra space. > > NeilBrown -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
