Invalid argument when creating a RAID-0 array

Invalid argument when creating a RAID-0 array

[Ari Pollak]

[Please CC me on replies]

I am currently trying to create a RAID-0 array using 5 SCSI drives with 
raidtools2 on Debian but it is failing. Any input would be appreciated. 
When I run 'mkraid /dev/md0', I get the following:

$ sudo mkraid /dev/md0
handling MD device /dev/md0
analyzing super-block
disk 0: /dev/sdb1, 4190400kB, raid superblock at 4190336kB
disk 1: /dev/sdc1, 4190400kB, raid superblock at 4190336kB
disk 2: /dev/sdd1, 4190400kB, raid superblock at 4190336kB
disk 3: /dev/sde1, 4180722kB, raid superblock at 4180608kB
disk 4: /dev/sdf1, 4190400kB, raid superblock at 4190336kB
/dev/md0: Invalid argument

Doing an strace of it gives the following reason for the Invalid argument:

open("/dev/md0", O_RDWR)                = 4
ioctl(4, 0x800c0930, 0xeffff7d8)        = -1 EINVAL (Invalid argument)
dup(2)                                  = 5
nfssvc(0x5)                             = 2
fstat64(5, {st_mode=S_IFCHR|0620, st_rdev=makedev(136, 2), ...}) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) 
= 0x7001e000
_llseek(5, 0, 0xeffff4a0, SEEK_CUR)     = -1 ESPIPE (Illegal seek)
write(5, "/dev/md0: Invalid argument\n", 27/dev/md0: Invalid argument
) = 27


Contents of my /etc/raidtab:
raiddev /dev/md0
         raid-level      0
         nr-raid-disks   5
         persistent-superblock 1
         chunk-size     4
         device          /dev/sdb1
         raid-disk       0
         device          /dev/sdc1
         raid-disk       1
         device          /dev/sdd1
         raid-disk       2
         device          /dev/sde1
         raid-disk       3
         device          /dev/sdf1
         raid-disk       4


Contents of /proc/mdstat:
Personalities : [raid0]
read_ahead not set
unused devices: <none>

kernel messages after running mkraid:
md: bind<sdb1,1>
md: bind<sdc1,2>
md: bind<sdd1,3>
md: bind<sde1,4>
md: bind<sdf1,5>
md: sdf1's event counter: 00000000
md: sde1's event counter: 00000000
md: sdd1's event counter: 00000000
md: sdc1's event counter: 00000000
md: sdb1's event counter: 00000000
too small chunk_size: 4096 < 8192
md: md0 stopped.
md: unbind<sdf1,4>
md: export_rdev(sdf1)
md: unbind<sde1,3>
md: export_rdev(sde1)
md: unbind<sdd1,2>
md: export_rdev(sdd1)
md: unbind<sdc1,1>
md: export_rdev(sdc1)
md: unbind<sdb1,0>
md: export_rdev(sdb1)

Re: Invalid argument when creating a RAID-0 array

[Neil Brown]

On Saturday June 14, ari@debian.org wrote:
> [Please CC me on replies]
> 
> I am currently trying to create a RAID-0 array using 5 SCSI drives with 
> raidtools2 on Debian but it is failing. Any input would be appreciated. 
> When I run 'mkraid /dev/md0', I get the following:
> 
....
>          chunk-size     4
....
> too small chunk_size: 4096 < 8192

Maybe use a bigger chunk size, 4K is rather small.
However I thought 4k would work.  Maybe you aren't using an i386, as
the minimum chunksize is currently connected with the system
pagesize.  What architecture are you using?

NeilBrown

Re: Invalid argument when creating a RAID-0 array

[Ari Pollak]

>>[Please CC me on replies]

>>too small chunk_size: 4096 < 8192
> 
> 
> Maybe use a bigger chunk size, 4K is rather small.
> However I thought 4k would work.  Maybe you aren't using an i386, as
> the minimum chunksize is currently connected with the system
> pagesize.  What architecture are you using?

Oops, I forgot to specify. I'm using an UltraSPARC on a Sun Enterprise 
450, using kernel 2.4.19 (I haven't had a chance to try .21 yet). I was 
just following the Software-RAID HOWTO, which said that for striping, 
chunksize didn't really matter.

RE: Invalid argument when creating a RAID-0 array

[Riley Williams]

Hi Ari.

 >>> too small chunk_size: 4096 < 8192

 >> Maybe use a bigger chunk size, 4K is rather small. However I
 >> thought 4k would work.  Maybe you aren't using an i386, as
 >> the minimum chunk size is currently connected with the system
 >> page size. What architecture are you using?

 > Oops, I forgot to specify. I'm using an UltraSPARC on a Sun
 > Enterprise 450, using kernel 2.4.19 (I haven't had a chance to
 > try .21 yet). I was just following the Software-RAID HOWTO,
 > which said that for striping, chunk size didn't really matter.

As you've discovered, the chunk size can't be less than the system
page size, and on the UltraSPARC platform, that's 8k - and the same
is true of most platforms other than ix86.

Providing you meet the above requirement, the RAID chunk size for
striping probably is irrelevant, but the page size requirement is
one that applies irrespective of any other requirements.

Best wishes from Riley.
---
 * Nothing as pretty as a smile, nothing as ugly as a frown.

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