Dne 15.8.2011 21:56, Jérôme Poulin napsal(a): > Good evening, > > I'm currently working on a project in which I use md-raid RAID1 with > Bitmap to "clone" my data from one disk to another and I would like to > know if this could cause corruption: > > The system has 2 SATA ports which are hotplug capable. > I created 2 partitions, 1 system (2GB), 1 data (1TB+). > I created to RAID1 using: > mdadm --create /dev/md0 --raid-devices=2 --bitmap=internal > --bitmap-chunk=4096 --metadata=1.0 /dev/sd[ab]1 > mdadm --create /dev/md1 --raid-devices=2 --bitmap=internal > --bitmap-chunk=65536 --metadata=1.0 /dev/sd[ab]2 > Forced sync_parallel on the system disk to be sure it rebuild first. > Formatted system ext3 and data ext4. > Both mounted using data=writeback. > > This system doesn't contain critical data but it contains backups on > the data partition. Once the data is in sync, I removed a disk and let > udev fail and remove the disk from the array, this is ArchLinux and > udev is set to mount the array using the incremental option, I added > --run to make sure it mounts even when a disk is missing. As of now, > eveything works as expected. > > Then what is different about a standard RAID1, I removed sdb and > replaced it with a brand new disk, copied the partition template from > the other one and added the new disk using mdadm -a on both arrays, it > synced and works, then swapping the other disk back only rebuilds > according to the bitmap, however sometimes it appears to make a full > rebuild which is alright. However once, after a day of modifications > and weeks after setting-up this RAID, at least 100 GB, it took seconds > to rebuild and days later it appeared to have encountered corruption, > the kernel complained about bad extents and fsck found errors in one > of the file I know it had modified that day. Does your scenario involve using two "external" drives, being swapped each time? 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. Best regards, Pavel. -- 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
