Thank you for your agile response, On Monday 04 August 2008 15:57, Conway S. Smith wrote: > Why are you thinking you'll have to totally recreate your raid anyway? > (I'm assuming you meant even if RAID5->6 reshape was possible, you'd > still be recreating it instead of reshaping). No actually, I'd really prefer to reshape it, but I've been somehow suspecting the bad news incoming. > > I see the following ways, supposing there's no reshape from raid5 > > to raid6. > > > > 1. Copy stuff to 2 new hdds (not raid'ed), create a slightly > > degraded raid6 out of old 3 hdds (making raid6 looks like it should > > have had 4), copy stuff over to raid6, and then add/reshape/etc. > > > > 2. Create a totally degraded raid6 with 2 new hdds, lacking 2 > > drives. Copy from current, operational, raid5, and then > > add/reshape/etc. > > > > 3. (risky) Check current raid5, and if it's checks ok, degrade it! > > Create a 4 hdd raid6 (4 out of 4 operational), copy stuff from > > degraded raid5, add/reshape/etc. > > I'd actually lean towards a fourth option: keeping the existing > RAID5, possibly reshaped to add more space on a new disk, and then > have another new disk as a hot spare. Not as good redundancy as > moving to RAID6, but much simpler w/ the current md feature set. > Except above you said you thought you'd have to recreate the array > anyway, in which case you may as well go to RAID6 now. Of the three > methods you show, I think #2 looks best, as it only involves one copy > step. The totally degraded RAID6 will be slow, but I doubt as slow > as another copy step. Keeping a RAID5 would be a great idea, and with a still rather small array, I think it could resync with a hot spare in about 4 hours. I'm on the safe side, I guess. Problem is, that I'd really like to move onto a RAID6 at some point, and, if I have to copy all the data to a temporary location, it's easier to do now, than few months later, with, say, 2 times more data. Crikey, I've realised that all my "ideas" are bad actually, they wouldn't survive any drive failure during the procedure. I think I'm gonna spend extra 100E on 3rd drive, and set up a slightly less degraded raid6. Knowing tricks, things tend to fail in worst possible moment. Best regards, MK PS: Sorry for some garbage at the end of my previous message, I have no idea what made gmail do that. -- 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
