i had a disk in a raid5 which i wanted to clone onto the hot spare... without going offline and without long periods without redundancy. a few folks have discussed using bitmaps and temporary (superblockless) raid1 mappings to do this... i'm not sure anyone has tried / reported success though. this is my success report. setup info: - kernel version 2.6.16.9 (as packaged by debian) - mdadm version 2.4.1 - /dev/md4 is the raid5 - /dev/sde1 is the disk in md4 i want to clone from - /dev/sdh1 is the hot spare from md4, and is the clone target - /dev/md5 is an unused md device name here are the exact commands i issued: mdadm -Gb internal --bitmap-chunk=1024 /dev/md4 mdadm /dev/md4 -r /dev/sdh1 mdadm /dev/md4 -f /dev/sde1 -r /dev/sde1 mdadm --build /dev/md5 -ayes --level=1 --raid-devices=2 /dev/sde1 missing mdadm /dev/md4 --re-add /dev/md5 mdadm /dev/md5 -a /dev/sdh1 ... wait a few hours for md5 resync... mdadm /dev/md4 -f /dev/md5 -r /dev/md5 mdadm --stop /dev/md5 mdadm /dev/md4 --re-add /dev/sdh1 mdadm --zero-superblock /dev/sde1 mdadm /dev/md4 -a /dev/sde1 this sort of thing shouldn't be hard to script :) the only times i was without full redundancy was briefly between the "-r" and "--re-add" commands... and with bitmap support the raid5 resync for each of those --re-adds was essentially zero. thanks Neil (and others)! -dean p.s. it's absolutely necessary to use "--build" for the temporary raid1 ... if you use --create mdadm will rightfully tell you it's already a raid component and if you --force it then you'll trash the raid5 superblock and it won't fit into the raid5 any more... - 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
