On Mon, 15 Aug 2011 22:42:06 +0200 Pavel Hofman <pavel.hofman@xxxxxxxxxxx> wrote: > > Dne 15.8.2011 22:25, Jérôme Poulin napsal(a): > > On Mon, Aug 15, 2011 at 4:21 PM, Pavel Hofman <pavel.hofman@xxxxxxxxxxx> wrote: > >> Does your scenario involve using two "external" drives, being swapped > >> each time? > > > > Yes, exactly, 3 or more drive, one stays in place, and the others get > > rotated off-site. > > > >> I am using such setup, but in order to gain the bitmap > >> performance effects, I have to run two mirrored RAID1s, i.e. two > >> bitmaps, each for its corresponding external disk. This setup has been > >> working OK for a few years now. > > > > Did you script something that stops the RAID and re-assemble it? The > > RAID must stay mounted in my case as there is live data (incremential > > backups, so even if the last file is incomplete it is not a problem.) > > I am working on wiki description of our backup solution. The priorities > got re-organized recently, looks like I should finish it soon :-) > > Yes, I have a script automatically re-assembling the array corresponding > to the added drive and starting synchronization. There is another script > checking synchronization status, run periodically from cron. When the > arrays are synced, it waits until the currently running backup job > finishes, shuts down the backup software (backuppc), unmounts the > filesystem to flush, removes the external drives from the array (we run > several external drives in raid0), does a few basic checks on the > external copy (mounting read-only, reading a directory) and puts the > external drives to sleep (hdparm -Y) for storing them outside of company > premises. > > Give me a few days, I will finish the wiki page and send you a link. > I'm not sure from you description whether the following describes exactly what you are doing or not, but this is how I would do it. As you say, you need two bitmaps. So if there are 3 drives A, X, Y where A is permanent and X and Y are rotated off-site, then I create two RAID1s like this: mdadm -C /dev/md0 -l1 -n2 --bitmap=internal /dev/A /dev/X mdadm -C /dev/md1 -l1 -n2 --bitmap=internal /dev/md0 /dev/Y mkfs /dev/md1; mount /dev/md1 ... Then you can remove either or both of X and Y and which each is re-added it will recover just the blocks that it needs. X from the bitmap of md0, Y from the bitmap of md1. 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
