On 07/10/2017 09:27 PM, Ram Ramesh wrote:
I shrunk md device to suit my needs and now I need to shrink the
partition of each component device so that I can reuse the unused
space on the component disks. Every google search that I encountered
only outlines a method where you fail, remove, re-partition, add, sync
each disk. With bitmap, I guess each sync will be very fast as data is
really not being changed. Since I have raid6, I should be able to work
on one disk at a time without much risk also.
However, is this the recommended method? Why not simply boot on a
rescue system, do not assemble the array, simply change all partitions
and reboot the original system so that the array will get assembled
the normal way? Is this too risky or inferior?
While we are at it, mdadm -E says
Avail Dev Size : 11720780943 (5588.90 GiB 6001.04 GB)
Array Size : 12348030976 (11776.00 GiB 12644.38 GB)
Used Dev Size : 6174015488 (2944.00 GiB 3161.10 GB)
What is Used Dev Size? Is is the last sector used or the number of
sectors used? If my current partition(s) start at 2048, does it mean I
should end the md partitions on or after 6174015488 or (6174015488+2048)?
How do I make mdadm scrub the entire array even though bit map says
there is no need?
Ramesh
My attempt to remove a drive repartition and readd did not work. mdadm
refused to readd the device. Any one know why? This is what I did.
sudo mdadm /dev/md0 --fail /dev/sdb1
sudo mdadm /dev/md0 --remove /dev/sdb1
sudo gdisk /dev/sdb
< shrunk the partition size so that /dev/sdb1 is 2048 - 6442452991 and
created /dev/sdb2 6442452992-11721045134>
New partition table:
Number Start (sector) End (sector) Size Code Name
1 2048 6442452991 3.0 TiB FD00 Linux RAID
2 6442452992 11721045134 2.5 TiB FD00 Linux RAID
sudo mdadm /dev/md0 --re-add /dev/sdb1
***mdadm: --re-add for /dev/sdb1 to /dev/md0 is not possible***
Why? I have enabled bit maps and /proc/mdstat shows that.
Any way, I simply added the drive and it is rebuilding. I thought I knew
what will happen. You live and learn.
Now I am happy that I did not redo the partition on more than one drive.
I will wait for expert advice before proceeding.
Ramesh
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