Hi, I'm hoping to shrink the per-component size of an active RAID1 array, so that I can transition the array to a smaller, faster set of drives. It appears I could do this by first shrinking the filesystem (ext3) with 'parted' as described here... http://www.gnu.org/software/parted/manual/html_mono/parted.html#SEC68 ...and then use 'mdadm' with the '--grow' and '--size' options to shrink my RAID1 array's extent on disks. But, I can't find a reference to doing exactly this online, the 'mdadm' man page is a little thin on 'grow' details, and there's at least one suggestion that the 'mdadm' man page is wrong about the units to use in the '--size' parameter. (See http://www.issociate.de/board/post/250478/error_in_mdadm_man_page.html ) So, could someone "in the know" give a sanity check to my plan? I've got a 2.6.12 kernel and I've got the following RAID1 arrays... # cat /proc/mdstat Personalities : [raid1] md1 : active raid1 sdc3[2] sdb3[1] sda3[0] 154087360 blocks [3/3] [UUU] md0 : active raid1 sdc1[1] sdb1[2] sda1[0] 104320 blocks [3/3] [UUU] unused devices: <none> I want to shrink /dev/md1 to about 70GB. The constituent physical partitions look like this... # fdisk /dev/sda Command (m for help): p Disk /dev/sda: 160.0 GB, 160041885696 bytes 255 heads, 63 sectors/track, 19457 cylinders Units = cylinders of 16065 * 512 = 8225280 bytes Device Boot Start End Blocks Id System /dev/sda1 1 13 104391 fd Linux raid autodetect /dev/sda2 14 274 2096482+ 82 Linux swap /dev/sda3 275 19457 154087447+ fd Linux raid autodetect I presume I should boot from a CD, then without /dev/md1 mounted, follow the instructions from the 'parted' docs to resize filesystem to 70000 megabytes (or is it mebibytes? the 'parted' doc isn't clear): # parted /dev/md1 (parted) resize 1 0 70000 (parted) quit Then, use 'mdadm' to shrink the array to the right size (which I'm assuming is 70000MiB*1024KiB/MiB == 71680000 kebibytes): # mdadm --grow /dev/md1 --size 71680000 Then reboot, and all should be well at the smaller size. My main concerns: (1) Are these the right steps? (Missing anything?) (2) Are the 'parted' units truly meGAbytes? (3) How should the 'mdadm' '--size' parameter be related to the 'parted' parameter? (Is the man bug report suggesting the '--size' must be specified in bytes, not kebibytes, accurate? Do I have to deduct the 128K superblock space, or is that done automatically?) Thanks for any guidance! - Gordon @ Bitzi - 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
