Problem with 3xRAID1 to RAID 0

Problem with 3xRAID1 to RAID 0

[Vladimir Strycek]

Hi,

I created to 3 x /dev/md1 to /dev/md3  which consist of six identical 
200GB hdd

my mdadm --detail --scan looks like

Proteus:/home/vladoportos# mdadm --detail --scan
ARRAY /dev/md1 level=raid1 num-devices=2 UUID=d1fadb29:cc004047:aabf2f31:3f044905
   devices=/dev/sdb,/dev/sda
ARRAY /dev/md2 level=raid1 num-devices=2 UUID=38babb4d:92129d4a:94d659f1:3b238c53
   devices=/dev/sdc,/dev/sdd
ARRAY /dev/md3 level=raid1 num-devices=2 UUID=a0406e29:c1f586be:6b3381cf:086be0c2
   devices=/dev/sde,/dev/sdf
ARRAY /dev/md0 level=raid1 num-devices=2 UUID=c04441d4:e15d900e:57903584:9eb5fea6
   devices=/dev/hdc1,/dev/hdd1


and mdadm.conf

DEVICE partitions
ARRAY /dev/md4 level=raid0 num-devices=3 UUID=1c8291ba:2d83cf54:2698ce30:e49b1e6c
   devices=/dev/md1,/dev/md2,/dev/md3
ARRAY /dev/md3 level=raid1 num-devices=2 UUID=a0406e29:c1f586be:6b3381cf:086be0c2
   devices=/dev/sde,/dev/sdf
ARRAY /dev/md2 level=raid1 num-devices=2 UUID=38babb4d:92129d4a:94d659f1:3b238c53
   devices=/dev/sdc,/dev/sdd
ARRAY /dev/md1 level=raid1 num-devices=2 UUID=d1fadb29:cc004047:aabf2f31:3f044905
   devices=/dev/sda,/dev/sdb
ARRAY /dev/md0 level=raid1 num-devices=2 UUID=c04441d4:e15d900e:57903584:9eb5fea6
   devices=/dev/hdc1,/dev/hdd1



as you can see i created than from md1-3 RAID0 - md4 its works fine... 
but i cant get it again after reboot i need to create it again...

I dont get it why it wont creat at boot...  any body had similar problem ?

Thanks for help and best regard
Vladimir

Re: Problem with 3xRAID1 to RAID 0

[Jim Klimov]

Hello Vladimir,

Tuesday, July 11, 2006, 11:41:31 AM, you wrote:

VS> Hi,

VS> I created to 3 x /dev/md1 to /dev/md3  which consist of six identical
VS> 200GB hdd

VS> my mdadm --detail --scan looks like

VS> Proteus:/home/vladoportos# mdadm --detail --scan
VS> ARRAY /dev/md1 level=raid1 num-devices=2
VS> UUID=d1fadb29:cc004047:aabf2f31:3f044905
VS>    devices=/dev/sdb,/dev/sda
VS> ARRAY /dev/md2 level=raid1 num-devices=2
VS> UUID=38babb4d:92129d4a:94d659f1:3b238c53
VS>    devices=/dev/sdc,/dev/sdd
VS> ARRAY /dev/md3 level=raid1 num-devices=2
VS> UUID=a0406e29:c1f586be:6b3381cf:086be0c2
VS>    devices=/dev/sde,/dev/sdf
VS> ARRAY /dev/md0 level=raid1 num-devices=2
VS> UUID=c04441d4:e15d900e:57903584:9eb5fea6
VS>    devices=/dev/hdc1,/dev/hdd1


VS> and mdadm.conf

VS> DEVICE partitions
VS> ARRAY /dev/md4 level=raid0 num-devices=3
VS> UUID=1c8291ba:2d83cf54:2698ce30:e49b1e6c
VS>    devices=/dev/md1,/dev/md2,/dev/md3
VS> ARRAY /dev/md3 level=raid1 num-devices=2
VS> UUID=a0406e29:c1f586be:6b3381cf:086be0c2
VS>    devices=/dev/sde,/dev/sdf
VS> ARRAY /dev/md2 level=raid1 num-devices=2
VS> UUID=38babb4d:92129d4a:94d659f1:3b238c53
VS>    devices=/dev/sdc,/dev/sdd
VS> ARRAY /dev/md1 level=raid1 num-devices=2
VS> UUID=d1fadb29:cc004047:aabf2f31:3f044905
VS>    devices=/dev/sda,/dev/sdb
VS> ARRAY /dev/md0 level=raid1 num-devices=2
VS> UUID=c04441d4:e15d900e:57903584:9eb5fea6
VS>    devices=/dev/hdc1,/dev/hdd1



VS> as you can see i created than from md1-3 RAID0 - md4 its works fine...
VS> but i cant get it again after reboot i need to create it again...

VS> I dont get it why it wont creat at boot...  any body had similar problem ?
I haven't had a problem like this, but taking a wild guess - did you
try putting the definitions in mdadm.conf in a different order?

In particular, you define md4 before the system knows anything about
the devices md[1-3]...

You can speed up the checks (I think) by using something like this
instead of rebooting full-scale, except for the last check to see if
it all actually works :)
mdadm --stop /dev/md4
mdadm --stop /dev/md3
mdadm --stop /dev/md2
mdadm --stop /dev/md1

mdadm -As
or
mdadm -Asc /etc/mdadm.conf.test

Also you seem to make the md[1-3] devices from whole disks.
Had you made them from partitions you could
1) Set a partition type to 0xfd so that a proper kernel could make
   your raid1 sets at boot-time and then make md4 correctly even
   with the current config file
2) Move the submirrors to another disk (i.e. a new larger one)
   if you needed to rebuild, upgrade, recover, etc. by just making
   a new partition of the same size.
   Also keep in mind that "200Gb" (and any other) disks of different
   models and makers can vary in size by several tens of megabytes...
   Bit me once with certain 36Gb SCSI disks which were somewhat
   larger than any competition, so we had to hunt for the same model
   to rebuild our array.

A question to the general public: am I wrong? :)
Are there any actual bonuses to making RAIDs on whole raw disks?

-- 
Best regards,
 Jim Klimov                            mailto:klimov@2ka.mipt.ru

Re: Problem with 3xRAID1 to RAID 0

[Mario 'BitKoenig' Holbe]

Jim Klimov <klimov@2ka.mipt.ru> wrote:
> Are there any actual bonuses to making RAIDs on whole raw disks?

You win 63 sectors (i.e. 32k) usually.


regards
   Mario
-- 
*axiom* welcher sensorische input bewirkte die output-aktion,
        den irc-chatter mit dem nick "dus" des irc-servers
        mittels eines kills zu verweisen?

Re: Problem with 3xRAID1 to RAID 0

[Christian Pernegger]

> Are there any actual bonuses to making RAIDs on whole raw disks?

Not if you're using regular md devices.

For partitionable md arrays using partitions seems a little strange to
me, since you then have partitions on a partition. That'd probably
make it difficult to just mount a single member of a mirror for data
recovery, etc ...

And Neil seems to favour initrd over kernel auto-detection / assembly anyhow.

FWIW, I use whole disks and limit the space used per disk to exactly
the rated capacity, i. e. floor ( ( GB * 10^9 ) / 1024 ) blocks with
the --size parameter.

Regards,

C.

Re: Problem with 3xRAID1 to RAID 0

[Neil Brown]

On Tuesday July 11, vladoportos@vladoportos.sk wrote:
> Hi,
> 
> I created to 3 x /dev/md1 to /dev/md3  which consist of six identical 
> 200GB hdd
> 
> my mdadm --detail --scan looks like
> 
> Proteus:/home/vladoportos# mdadm --detail --scan
> ARRAY /dev/md1 level=raid1 num-devices=2 UUID=d1fadb29:cc004047:aabf2f31:3f044905
>    devices=/dev/sdb,/dev/sda
> ARRAY /dev/md2 level=raid1 num-devices=2 UUID=38babb4d:92129d4a:94d659f1:3b238c53
>    devices=/dev/sdc,/dev/sdd
> ARRAY /dev/md3 level=raid1 num-devices=2 UUID=a0406e29:c1f586be:6b3381cf:086be0c2
>    devices=/dev/sde,/dev/sdf
> ARRAY /dev/md0 level=raid1 num-devices=2 UUID=c04441d4:e15d900e:57903584:9eb5fea6
>    devices=/dev/hdc1,/dev/hdd1
> 
> 
> and mdadm.conf
> 
> DEVICE partitions
> ARRAY /dev/md4 level=raid0 num-devices=3 UUID=1c8291ba:2d83cf54:2698ce30:e49b1e6c
>    devices=/dev/md1,/dev/md2,/dev/md3
> ARRAY /dev/md3 level=raid1 num-devices=2 UUID=a0406e29:c1f586be:6b3381cf:086be0c2
>    devices=/dev/sde,/dev/sdf
> ARRAY /dev/md2 level=raid1 num-devices=2 UUID=38babb4d:92129d4a:94d659f1:3b238c53
>    devices=/dev/sdc,/dev/sdd
> ARRAY /dev/md1 level=raid1 num-devices=2 UUID=d1fadb29:cc004047:aabf2f31:3f044905
>    devices=/dev/sda,/dev/sdb
> ARRAY /dev/md0 level=raid1 num-devices=2 UUID=c04441d4:e15d900e:57903584:9eb5fea6
>    devices=/dev/hdc1,/dev/hdd1

Get rid of the "devices=..." lines.  You don't want them - though they
aren't causing a problem yet...

What happens if you
  mdadm --stop --scan
  mdadm --assemble --scan

What gets assembled?

NeilBrown