While the reshape is running, you can cat /proc/mdstat to see some status. The output from this command looks like this:

ahbanks@raid:~$ cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid5 sdb3[2] sda3[0] sdc4[1]
1232688064 blocks super 0.91 level 5, 64k chunk, algorithm 2 [3/3] [UUU]
[===================>.] reshape = 99.4% (1226222424/1232688064) finish=4.1min speed=26164K/sec

As you can tell, I did that when the reshape was almost done!


ahbanks@raid:~$ sudo mdadm -D /dev/md0
[sudo] password for ahbanks:
/dev/md0:
Version : 00.91
Creation Time : Sat Jan 24 14:37:13 2009
Raid Level : raid5
Array Size : 1232688064 (1175.58 GiB 1262.27 GB)
Used Dev Size : 1232688064 (1175.58 GiB 1262.27 GB)
Raid Devices : 3
Total Devices : 3
Preferred Minor : 0
Persistence : Superblock is persistent

Update Time : Thu Feb 5 17:22:26 2009
State : clean, recovering
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0

Layout : left-symmetric
Chunk Size : 64K

Reshape Status : 99% complete
Delta Devices : 1, (2->3)

UUID : 24ce66b9:093ac8f1:b5fcf7a2:8379ebaf (local to host jupiter)
Events : 0.817352

Number Major Minor RaidDevice State
0 8 3 0 active sync /dev/sda3
1 8 36 1 active sync /dev/sdc4
2 8 19 2 active sync /dev/sdb3
ahbanks@raid:~$

This gives us even more data. Note the device size, 1175 GB, even though there are 3 drives. After this process finishes, we see:

ahbanks@raid:~$ sudo mdadm -D /dev/md0
/dev/md0:
Version : 00.90
Creation Time : Sat Jan 24 14:37:13 2009
Raid Level : raid5
Array Size : 2465376128 (2351.17 GiB 2524.55 GB)
Used Dev Size : 1232688064 (1175.58 GiB 1262.27 GB)
Raid Devices : 3
Total Devices : 3
Preferred Minor : 0
Persistence : Superblock is persistent

Update Time : Thu Feb 5 20:37:20 2009
State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0

Layout : left-symmetric
Chunk Size : 64K

UUID : 24ce66b9:093ac8f1:b5fcf7a2:8379ebaf (local to host jupiter)
Events : 0.821960

Number Major Minor RaidDevice State
0 8 3 0 active sync /dev/sda3
1 8 36 1 active sync /dev/sdc4
2 8 19 2 active sync /dev/sdb3

Once the reshape is done, the device has the full 2351 GB.

Now, I extended the JFS filesystem.

sudo mount -o remount,resize /dev/md0

This took a few minutes to run, then:


ahbanks@raid:~$ df -h
Filesystem Size Used Avail Use% Mounted on
/dev/md0 2.3T 363G 2.0T 16% /mnt/raid

Much better!

Now, I’m kicking myself. If I’ve learned anything from building this array, it’s easy, really. Grab some disks and do it. Next, I’ll look at the hardware costs of an inexpensive system.

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