RAID adventures

Bill Davidsen davidsen at tmr.com
Mon Jul 19 03:03:00 UTC 2010


Konstantin Svist wrote:
>   I've been playing around with RAID config and may have finally messed 
> it up.
> 
> Initially, I created the array with 3 300G drives:
> # mdadm --create --verbose /dev/md0 --level=5 --raid-devices=3 /dev/sda4 
> /dev/sdb1 /dev/sdc1
> # mkfs.ext4 -v -m 0.01 -E stride=16,stripe-width=32 /dev/md0
> 
> It's been working nicely so far, and I decided to add a 4th 300G drive:
> # mdadm --grow --raid-devices=4 --backup-file=/root/grow_md0.bak /dev/md0
> 
> That finished overnight, while I looked around and found that chunk size 
> of 512 should work better. I unmounted the FS and ran
> # mdadm --grow -c 512 --backup-file=/root/grow_md0_rechunk.bak /dev/md0
> mdadm: component size 293033536K is not a multiple of chunksize 512K
> 
> so I sized it down a bit:
> # mdadm --grow -z 293033472 --backup-file=/root/grow_md0_size.bak /dev/md0
> 
> and then back to resizing chunks:
> mdadm --grow -c 512 --backup-file=/root/grow_md0_rechunk.bak /dev/md0
> 
> It's running right now:
> # cat /proc/mdstat
> Personalities : [raid6] [raid5] [raid4]
> md0 : active raid5 sdd1[3] sda4[0] sdc1[2] sdb1[1]
>        293033472 blocks super 0.91 level 5, 64k chunk, algorithm 2 [4/4] 
> [UUUU]
>        [====>................]  reshape = 22.7% (66540032/293033472) 
> finish=947.3min speed=3984K/sec
> 
> 
> But just now I tried to mount the filesystem and it's failing:
> EXT4-fs (md0): bad geometry: block count 146516768 exceeds size of 
> device (73258368 blocks)
> 
> Here's the question, then: am I royally screwed or is my data still 
> there? How do I recover?

May I suggest trying this on the linux-raid list? Not that's it's off-topic 
here, just that people there may have faster/better answers.

-- 
Bill Davidsen <davidsen at tmr.com>
   "We have more to fear from the bungling of the incompetent than from
the machinations of the wicked."  - from Slashdot


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