"mdadm -Dsv" output

"mdadm -Dsv" output

[Adrian Sandor]

Hi, this is not a big issue, but I'm unsatisfied with the output of mdadm -Dsv. I'm using mdadm 3.0.
Here's the output on one machine:

ARRAY /dev/md/0level=raid1 num-devices=2 metadata=0.90 UUID=91407351:9059f7b0:38ae7154:38049e4e
   devices=/dev/sdb1,/dev/sda1
ARRAY /dev/md/1level=raid1 num-devices=2 metadata=0.90 UUID=d1776dd8:db91f423:99830b25:d3f7cedd
   devices=/dev/sdc1,/dev/sdb3

The devices are shown as "/dev/md/n" instead of "/dev/mdn", and there's no space before "level".

On another machine I got:

ARRAY /dev/md1level=raid1 num-devices=2 metadata=0.90 UUID=88c8442e:4f17f837:bde095a2:d13819de
   devices=/dev/sdc1,/dev/sdd1
ARRAY /dev/md0level=raid10 num-devices=4 metadata=0.90 UUID=95e59d50:2eae3beb:bde095a2:d13819de
   devices=/dev/sda3,/dev/sdb1,/dev/sdc2,/dev/sdd2

Here it's showing "/dev/mdn", but again there's no space before "level", and the devices are not in order.

Third machine:

ARRAY /dev/md/0_0level=raid1 num-devices=2 metadata=0.90 UUID=24302b7f:d959dadb:5af0b895:7edd2b0f
   devices=/dev/sdb1,/dev/sda1
ARRAY /dev/md/3_0level=raid10 num-devices=4 metadata=0.90 UUID=19f4b34c:0ec56553:6bb0b7af:9ec1922b
   devices=/dev/sda3,/dev/sdb3,/dev/sdc3,/dev/sdd3
ARRAY /dev/md/2_0level=raid1 num-devices=2 metadata=0.90 UUID=d232d5b6:7d276c52:b7fe7b09:538f0c09
   devices=/dev/sdc2,/dev/sdd2
ARRAY /dev/md/1_0level=raid1 num-devices=2 metadata=0.90 UUID=2337ad91:997bfcc0:53f8cadc:1d167f18
   devices=/dev/sdc1,/dev/sdd1

Back to "/dev/md/n", but now there's an extra "_0" ?! Where did that come from?
Again, no space and not in order.
And on a 4th machine, the output is similar to the 3rd one.

All machines are running Gentoo Linux amd64 and the same mdadm version (3.0)

Another question is whether there's another way to output this information, that's more consistent, and more suitable for parsing by a program.

Thanks
Adrian



      

Re: "mdadm -Dsv" output

[Adrian Sandor]

Well, I figured out a few things after spending some time with the mdadm man page:
- the "_0" suffix is possibly related to the "homehost" (I guess the computer's hostname was modified) and auto-assembly; I have both "n" and "n_0" symlinks in /dev/md on those machines, pointing to the same "/dev/mdn" devices
- I can use /proc/mdstat for info instead; it looks decent, uses "mdn" names, can be accessed as a normal user, and doesn't require mdadm
- there's also /proc/partitions - very nifty

Still, I would like the output of mdadm -Dsv to be improved (regarding formatting and consistency).

Adrian


________________________________

Hi, this is not a big issue, but I'm unsatisfied with the output of mdadm -Dsv. I'm using mdadm 3.0.
Here's the output on one machine:

ARRAY /dev/md/0level=raid1 num-devices=2 metadata=0.90 UUID=91407351:9059f7b0:38ae7154:38049e4e
   devices=/dev/sdb1,/dev/sda1
ARRAY /dev/md/1level=raid1 num-devices=2 metadata=0.90 UUID=d1776dd8:db91f423:99830b25:d3f7cedd
   devices=/dev/sdc1,/dev/sdb3

The devices are shown as "/dev/md/n" instead of "/dev/mdn", and there's no space before "level".

On another machine I got:

ARRAY /dev/md1level=raid1 num-devices=2 metadata=0.90 UUID=88c8442e:4f17f837:bde095a2:d13819de
   devices=/dev/sdc1,/dev/sdd1
ARRAY /dev/md0level=raid10 num-devices=4 metadata=0.90 UUID=95e59d50:2eae3beb:bde095a2:d13819de
   devices=/dev/sda3,/dev/sdb1,/dev/sdc2,/dev/sdd2

Here it's showing "/dev/mdn", but again there's no space before "level", and the devices are not in order.

Third machine:

ARRAY /dev/md/0_0level=raid1 num-devices=2 metadata=0.90 UUID=24302b7f:d959dadb:5af0b895:7edd2b0f
   devices=/dev/sdb1,/dev/sda1
ARRAY /dev/md/3_0level=raid10 num-devices=4 metadata=0.90 UUID=19f4b34c:0ec56553:6bb0b7af:9ec1922b
   devices=/dev/sda3,/dev/sdb3,/dev/sdc3,/dev/sdd3
ARRAY /dev/md/2_0level=raid1 num-devices=2 metadata=0.90 UUID=d232d5b6:7d276c52:b7fe7b09:538f0c09
   devices=/dev/sdc2,/dev/sdd2
ARRAY /dev/md/1_0level=raid1 num-devices=2 metadata=0.90 UUID=2337ad91:997bfcc0:53f8cadc:1d167f18
   devices=/dev/sdc1,/dev/sdd1

Back to "/dev/md/n", but now there's an extra "_0" ?! Where did that come from?
Again, no space and not in order.
And on a 4th machine, the output is similar to the 3rd one.

All machines are running Gentoo Linux amd64 and the same mdadm version (3.0)

Another question is whether there's another way to output this information, that's more consistent, and more suitable for parsing by a program.

Thanks
Adrian


      

Re: "mdadm -Dsv" output

[Neil Brown]

On Tue, 29 Jun 2010 16:39:47 -0700 (PDT)
Adrian Sandor <aditsu@yahoo.com> wrote:

> Well, I figured out a few things after spending some time with the mdadm man page:
> - the "_0" suffix is possibly related to the "homehost" (I guess the computer's hostname was modified) and auto-assembly; I have both "n" and "n_0" symlinks in /dev/md on those machines, pointing to the same "/dev/mdn" devices
> - I can use /proc/mdstat for info instead; it looks decent, uses "mdn" names, can be accessed as a normal user, and doesn't require mdadm
> - there's also /proc/partitions - very nifty
> 
> Still, I would like the output of mdadm -Dsv to be improved (regarding formatting and consistency).
> 

Thanks for your comments.

The missing space before "level" is fixed in newer versions of mdadm.

The variability in the array name (/dev/md0 vs /dev/md/0 vs /dev/md/0_0) does
appear clumsy I agree.
The name should be the name that was used to assemble the array.  If mdadm
was asked to choose a name automatically it will do the best it case, which
is different depending on the style of metadata used.

With the original 0.90 metadata, the array only knows a number that can
identify it, so you get /dev/mdNN - e.g. /dev/md0
With 1.x metadata, the array knows a name, so you get /dev/md/XXXX, e.g.
  /dev/md/0 or /dev/md/home
depending on what name was used to create it.

If the array appears to come from a different host, then mdadm appends a _NN
suffix to ensure the name doesn't conflict with the name of a local array.

NeilBrown