On Thursday December 13, jeff@xxxxxxx wrote: > > What you could do is set the number of devices in the array to 3 so > > they it always appears to be degraded, then rotate your backup drives > > through the array. The number of dirty bits in the bitmap will > > steadily grow and so resyncs will take longer. Once it crosses some > > threshold you set the array back to having 2 devices to that it looks > > non-degraded and clean the bitmap. Then each device will need a full > > resync after which you will get away with partial resyncs for a while. > > I don't undertand why clearing the bitmap causes a rebuild of > all devices. I think I have a conceptual misunderstanding. Consider > a RAID-1 and three physical disks involved, A,B,C > > 1) A and B are in the RAID, everything is synced > 2) Create a bitmap on the array > 3) Fail + remove B > 4) Hot add C, wait for C to sync > 5) Fail + remove C > 6) Hot add B, wait for B to resync > 7) Goto step 3 > > I understand that after a while we might want to clean the bitmap > and that would trigger a full resync for drives B and C. I don't > understand why it would ever cause a resync for drive A. You are exactly correct. That is what I meant, though I probably didn't express it very clearly. After you clean out the bitmap, any devices that are not in the array at that time will need a full resync to come back in to the array. 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
