RAID5 Shrinking array-size nearly killed the system
flat view
From: Rory Jaffe <hidden>
Date: 2011-03-12 04:58:09
Using Ubuntu 10.10 mdadm v 3.2. ext4 filesystem. I wanted to shrink from 6 disks to 4. I have about 2TB of files on the disks. So, I ran $ sudo mdadm -G -n 4 /dev/md0 which gave the message: mdadm: this change will reduce the size of the array. use --grow --array-size first to truncate array. e.g. mdadm --grow /dev/md0 --array-size 5857612608 then ran $ sudo mdadm --grow /dev/md0 --array-size 5857612608 and started testing the filesystem prior to reducing the array. I quickly found out that the filesystem was broken. It was broken enough that I couldn't even get access to commands, including sudo, mdadm, reboot, and ls. I had to power down the system and restart it. There were a number of disk errors, but managed to restart the system and it looks like there wasn't much damage. fstab is listed after my questions. Questions: 1. Is there a safer way to shrink the file system prior to reducing the number of disks in the array? 2. Is there a way of rearranging the files and directories to make the file system shrink safer? 3. Is there something I did that caused the crash? Thanks-Rory # /etc/fstab: static file system information. # # Use 'blkid -o value -s UUID' to print the universally unique identifier # for a device; this may be used with UUID= as a more robust way to name # devices that works even if disks are added and removed. See fstab(5). # # <file system> <mount point> <type> <options> <dump> <pass> proc /proc proc nodev,noexec,nosuid 0 0 # / was on /dev/md0 during installation UUID=9a978b70-e034-4d79-9e1d-237a67b553d5 / ext4 commit=60,errors=remount-ro,usrjquota=aquota.user,grpjquota=aquota.group,jqfmt=vfsv1,barrier=0 0 1 # /boot was on /dev/sdb1 during installation UUID=5beb5144-6d2f-4a73-b9e9-442355d8f529 /boot ext2 defaults 0 2 # swap was on /dev/sda1 during installation UUID=31660a21-3f99-4ffb-81cc-501dc6ce5de7 none swap sw 0 0 # swap was on /dev/sdc1 during installation UUID=f168588d-8b9e-45c3-b9ae-f90f66906616 none swap sw 0 0 # swap was on /dev/sdd1 during installation UUID=05cadc48-59df-479e-b5ed-b9e9322cb905 none swap sw 0 0 # swap was on /dev/sde1 during installation UUID=61fba94d-e6c5-4a58-b0cd-9d878b55b65c none swap sw 0 0 # swap was on /dev/sdf1 during installation UUID=47737641-7555-4cbc-9bf6-508c9f2035bc none swap sw 0 0 # swap was on /dev/sdg1 during installation UUID=ad06f3d6-a6ec-445a-bcfb-427fec72725b none swap sw 0 0 -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html