mdadm RAID5 Grow

mdadm RAID5 Grow

[mickg]

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
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Re: mdadm RAID5 Grow

[Neil Brown]

On Wednesday October 4, mickg@mickg.net wrote:
> 
> 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

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.

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

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

NeilBrown

Re: mdadm RAID5 Grow

[mickg]

Neil Brown wrote:
> On Wednesday October 4, mickg@mickg.net wrote:
>> 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
> 
> 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.
> 
>> Would it need to be unmounted to work properly (It is currently mounted
>> under lvm)?
> 
> No.  unmounting isn't needed and won't make any difference.
> 
> NeilBrown
> -
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
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

Re: mdadm RAID5 Grow

[Neil Brown]

On Thursday October 5, mickg@mickg.net wrote:
> Neil Brown wrote:
> > On Wednesday October 4, mickg@mickg.net wrote:
> >> 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
> > 
> > It shouldn't do that.... 
> > Can you 
> >   strace -o /tmp/trace -s 300 mdadm --grow .....
...
> open("/sys/block/md0/md/component_size", O_RDONLY) = -1 ENOENT (No such file or directory)

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

Re: mdadm RAID5 Grow

[mickg]

Neil Brown wrote:
> On Thursday October 5, mickg@mickg.net wrote:
>> Neil Brown wrote:
>>> On Wednesday October 4, mickg@mickg.net wrote:
>>>> 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
>>> It shouldn't do that.... 
>>> Can you 
>>>   strace -o /tmp/trace -s 300 mdadm --grow .....
> ...
>> open("/sys/block/md0/md/component_size", O_RDONLY) = -1 ENOENT (No such file or directory)
> 
> 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.
> 
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
> NeilBrown
> -
> To unsubscribe from this list: send the line "unsubscribe linux-raid" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: mdadm RAID5 Grow

[Neil Brown]

On Thursday October 5, mickg@mickg.net wrote:
> 
> 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 ?

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

Re: mdadm RAID5 Grow

[Bill Davidsen]

mickg wrote:
> Neil Brown wrote:
>> On Thursday October 5, mickg@mickg.net wrote:
>>> Neil Brown wrote:
>>>> On Wednesday October 4, mickg@mickg.net wrote:
>>>>> 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
>>>> It shouldn't do that.... Can you   strace -o /tmp/trace -s 300 
>>>> mdadm --grow .....
>> ...
>>> open("/sys/block/md0/md/component_size", O_RDONLY) = -1 ENOENT (No 
>>> such file or directory)
>>
>> 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.
>>
> 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 
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 <davidsen@tmr.com>
  CTO TMR Associates, Inc
  Doing interesting things with small computers since 1979