mdadm RAID5 Grow

I have been trying to run:
mdadm --grow /dev/md0 --raid-devices=6 --backup-file /backup_raid_grow I get:
mdadm: Need to backup 1280K of critical section..
mdadm: /dev/md0: Cannot get array details from sysfs

Software versions:
mdadm version 2.5.3, kernel 2.6.17.13

Note that /dev/md0 does in fact have 6 drives, with 4+2 spares:

linux-nas:~/source/mdadm-2.5.3 # mdadm -D /dev/md0 /dev/md0:

        Version : 00.90.03
  Creation Time : Mon Dec 31 20:20:05 2001
     Raid Level : raid5
     Array Size : 937681536 (894.24 GiB 960.19 GB)
    Device Size : 312560512 (298.08 GiB 320.06 GB)

Raid Devices : 4
Total Devices : 6
Preferred Minor : 0
Persistence : Superblock is persistent

Update Time : Thu Oct 5 00:24:18 2006
State : clean
Active Devices : 4
Working Devices : 6
Failed Devices : 0
Spare Devices : 2

Layout : left-symmetric
Chunk Size : 128K

UUID : 0d4e2bae:95de9dc6:4bf9f695:9e1a48be
Events : 0.988859

Number Major Minor RaidDevice State
0 8 209 0 active sync /dev/sdn1
1 8 145 1 active sync /dev/sdj1
2 8 129 2 active sync /dev/sdi1
3 8 161 3 active sync /dev/sdk1

4 8 192 - spare /dev/sdm
5 8 176 - spare /dev/sdl

As I said, I am getting an error resizing the array.

Would it need to be unmounted to work properly (It is currently mounted under lvm)?

Thank you in advance,
mickg

View this message in context: http://www.nabble.com/mdadm-RAID5-Grow-tf2386446.html#a6652499
Sent from the linux-raid mailing list archive at Nabble.com.

It shouldn't do that....
Can you
strace -o /tmp/trace -s 300 mdadm --grow .....

and send a copy of /tmp/trace. I'd like to see how far it gets at reading information from sysfs.

No. unmounting isn't needed and won't make any difference.

NeilBrown

strace mdadm --grow /dev/md0 --raid-devices=6 --backup-file /backup_raid_grow

execve("/sbin/mdadm", ["mdadm", "--grow", "/dev/md0", "--raid-devices=6", "--backup-file", "/backup_raid_grow"], [/* 68 vars */]) = 0

brk(0)                                  = 0x8076000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3

fstat64(3, {st_mode=S_IFREG|0644, st_size=107351, ...}) = 0
mmap2(NULL, 107351, PROT_READ, MAP_PRIVATE, 3, 0) = 0xa7fa8000
close(3) = 0
open("/lib/libc.so.6", O_RDONLY) = 3
read(3, "\177ELF\1\1\1\0\0\0\0\0\0\0\0\0\3\0\3\0\1\0\0\0\300Y\1"..., 512) = 512
fstat64(3, {st_mode=S_IFREG|0755, st_size=1404242, ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xa7fa7000
mmap2(NULL, 1176988, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0xa7e87000
madvise(0xa7e87000, 1176988, MADV_SEQUENTIAL|0x1) = 0
mmap2(0xa7fa0000, 16384, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x118) = 0xa7fa0000
mmap2(0xa7fa4000, 9628, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0xa7fa4000
close(3) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xa7e86000
set_thread_area({entry_number:-1 -> 6, base_addr:0xa7e866b0, limit:1048575, seg_32bit:1, contents:0, read_exec_only:0, limit_in_pages:1, seg_not_present:0, useable:1}) = 0

mprotect(0xa7fa0000, 8192, PROT_READ)   = 0
munmap(0xa7fa8000, 107351)              = 0
time(NULL)                              = 1160052126
getpid()                                = 8461
brk(0)                                  = 0x8076000
brk(0x8097000)                          = 0x8097000
open("/etc/mdadm.conf", O_RDONLY)       = 3
fstat64(3, {st_mode=S_IFREG|0644, st_size=154, ...}) = 0
mmap2(NULL, 131072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xa7e66000
read(3, "DEVICE partitions\nARRAY /dev/md0"..., 131072) = 154
read(3, "", 131072)                     = 0
read(3, "", 131072)                     = 0
close(3)                                = 0
munmap(0xa7e66000, 131072)              = 0
open("/dev/md0", O_RDWR)                = 3

fstat64(3, {st_mode=S_IFBLK|0640, st_rdev=makedev(9, 0), ...}) = 0
ioctl(3, 0x800c0910, 0xafc4a024) = 0
ioctl(3, 0x80480911, 0xafc4a0a8) = 0
fstat64(1, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 3), ...}) = 0
mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0xa7fc2000 write(1, "mdadm: Need to backup 1280K of c"..., 50mdadm: Need to backup 1280K of critical section.. ) = 50
fstat64(3, {st_mode=S_IFBLK|0640, st_rdev=makedev(9, 0), ...}) = 0 open("/sys/block/md0/md/component_size", O_RDONLY) = -1 ENOENT (No such file or directory) write(2, "mdadm: /dev/md0: Cannot get arra"..., 53mdadm: /dev/md0: Cannot get array details from sysfs ) = 53
exit_group(1) = ?
Process 8461 detached

...

So it couldn't open .../component_size. That was added prior to the release of 2.6.16, and you are running 2.6.17.13 so the kernel certainly supports it.
Most likely explanation is that /sys isn't mounted.
Do you have a "/sys"?
Is it mounted?
Can you "ls -l /sys/block/md0/md" ??

Maybe you need to
mkdir /sys
mount -t sysfs sysfs /sys

and try again.

NeilBrown

Worked like a charm!

Thank you!

There is a
sysfs /sys sysfs noauto 0 0
line in /etc/fstab
I am assuming noauto is the culprit?

Should it be made to automount ?

mickg

Maybe. You could try and see...
But I suggest checking with someone who knows about these details in your particular distro.
Maybe there is some init.d script that is meant to "mount /sys" and some appropriate time. Quite possibly it is mean to be mounted *before* other 'auto' filesystems in fstab.

NeilBrown

I will belatedly add that experience shows that /proc and /sys are optional (and can in theory be mounted other places), in practice a lot of software depends on them being present and in the usual place.

bill davidsen <[email protected]>
 CTO TMR Associates, Inc
 Doing interesting things with small computers since 1979