> Look in the mdadm source code, particularly at restripe.c
>
> Also
> make test_stripe
>
> make a program the the test suite uses for verify data correctness.
>
> That should give you enough hints to get you started.
Hi Neil,
I'm trying to use the "test_stripe" binary, just to
confirm the operation, in test mode (no save nor restore).
Unfortunately, it seems not work properly, in my hands.
I created a 4 disks RAID-6 (/dev/loop[0-3]), with:
mdadm -C /dev/md111 -l 6 -n 4 --chunk=64 /dev/loop[0-3]
Filled the array from urandom:
dd if=/dev/urandom of=/dev/md111
And tried:
./test_stripe test file_test.raw 4 65536 6 2 65536 $[ 65536 * 3 ] /dev/loop[0-3]
This returns:
0->0
1->1
P(2) wrong at 1
Q(3) wrong at 1
0->3
1->0
P(1) wrong at 2
Q(2) wrong at 2
0->2
1->3
P(0) wrong at 3
Q(1) wrong at 3
The array filled with "0" does not return any error.
Am'I missing something or the code has problems?
An other question, I noticed the code uses an array of
"offsets" which seem to be filled with "0" and never
changed.
Is this really wanted?
Is the offset information the one found per component
using "mdadm -E ..." or /sys/class/block/mdX/md/rdX/offset?
What's the relation with the "start" parameter of "test_stripe"?
Thanks in advance for any hints or suggestions.
The md device is:
/dev/md111:
Version : 1.2
Creation Time : Sat Feb 5 17:48:49 2011
Raid Level : raid6
Array Size : 524160 (511.96 MiB 536.74 MB)
Used Dev Size : 262080 (255.98 MiB 268.37 MB)
Raid Devices : 4
Total Devices : 4
Persistence : Superblock is persistent
Update Time : Sat Feb 5 18:19:45 2011
State : clean
Active Devices : 4
Working Devices : 4
Failed Devices : 0
Spare Devices : 0
Layout : left-symmetric
Chunk Size : 64K
Name : lazy.lzy:111 (local to host lazy.lzy)
UUID : b794fb80:c4006853:47761570:3d97a1d2
Events : 42
Number Major Minor RaidDevice State
0 7 0 0 active sync /dev/loop0
1 7 1 1 active sync /dev/loop1
2 7 2 2 active sync /dev/loop2
3 7 3 3 active sync /dev/loop3
bye,
--
piergiorgio
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