well that part is optional... i wasn't replacing the disk right away anyhow -- it had just exhibited its first surface error during SMART and i thought i'd try moving the data elsewhere just for the experience of it. -dean On Thu, 22 Jun 2006, Ming Zhang wrote: > Hi Dean > > Thanks a lot for sharing this. > > I am not quite understand about these 2 commands. Why we want to add a > pre-failing disk back to md4? > > mdadm --zero-superblock /dev/sde1 > mdadm /dev/md4 -a /dev/sde1 > > Ming > > > On Sun, 2006-04-23 at 18:40 -0700, dean gaudet wrote: > > 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 > - 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
