1. Would the re-sync of the RAID5 wait for the re-sync of the RAID1, since 2 different arrays depend on the same device? 2. Will the "bitmap of potentially dirty blocks" be able to keep a disk in the array if it has bad blocks? 3. Will RAID1 be able to re-sync to another disk if the source disk has bad blocks? Even if they are un-correctable? Once the re-sync is done, then RAID5 could re-construct the missing data, and correct the RAID1 array. Ouch!, seems like a catch 22. RAID5 should go first and correct the bad blocks first, and then, any new bad blocks found during the RAID1 re-sync. But, the bitmap would need to be quad-state (synced, right is good, left is good, both are bad). Since RAID1 can have more than 2 devices, maybe 1 bit per device (synced, not synced). The more I think, the harder it gets! :) If 1, 2 and 3 above are all yes, then it seems like a usable workaround. And, in the future, maybe RAID5 arrays would be made up of RAID1 arrays with only 1 disk each. Using grow to copy a failing disk to another (RAID1), then removing the failing disk. Then shrinking the RAID1 back to 1 disk. Then there would be no window. Using this method, #1 above is irrelevant, or less relevant! Guy -----Original Message----- From: linux-raid-owner@xxxxxxxxxxxxxxx [mailto:linux-raid-owner@xxxxxxxxxxxxxxx] On Behalf Of Neil Brown Sent: Wednesday, January 12, 2005 9:06 PM To: Guy Cc: 'maarten'; linux-raid@xxxxxxxxxxxxxxx Subject: RE: Spares and partitioning huge disks On Saturday January 8, bugzilla@xxxxxxxxxxxxxxxx wrote: > > Guy says: > But, I could tell md which disk I want to spare. After all, I know which > disk I am going to fail. Maybe even an option to mark a disk as "to be > failed", which would cause it to be spared before it goes off-line. Then md > could fail the disk after it has been spared. Neil, add this to the wish > list! :) Once the "bitmap of potentially dirty blocks" is working, this could be done in user space (though there would be a small window). - fail out the chosen drive. - combine it with the spare in a raid1 with no superblock - add this raid1 back into the main array. - md will notice that it has recently been removed and will only rebuild those blocks which need to be rebuilt - wait for the raid1 to fully sync - fail out the drive you want to remove. You only have a tiny window where the array is degraded, and if we were to allow an md array to block all IO requests for a time, you could make that window irrelevant. 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 - 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
