Re: Mdadm, udev and fakeraid?

[Seblu <seblu@seblu.net>]

On Tue, Apr 5, 2011 at 8:20 AM, NeilBrown <neilb@suse.de> wrote:
> On Sun, 3 Apr 2011 18:03:50 +0200 Seblu <seblu@seblu.net> wrote:
>
>> Hello,
>>
>> In the following commit, udev rules load isw_raid (fakeraid). From my
>> test, this doesnt work. I have to call dmraid to have something
>> working.
>> http://neil.brown.name/git?p=mdadm;a=commit;h=475a01b8bce8575dd1b2ab6495e65e854702ac0e
>>
>> isw_raid is only fakeraid devices? mdadm is able to mount fakeraid partition?
>>
>
> I'm sorry but I cannot parse those questions successfully so I'm not sure
> what you are asking.

Hello Neil,

in my previous mail, i used word fakeraid about raid created with
dmraid and i used softraid about raid created with mdadm. it was not
clear.

So my question was about compatibily. Raids created by dmraid can be
assembled with mdadm and vice versa?

> Both dmraid and mdadm can manage some 'fakeraid' arrays.  dmraid supports a
> wider variety.  mdadm supports raid1 and raid5 more completely than dmraid
> does.
mdadm -> create soft raid for linux  (now there is new format: ddf and imsm) ?
dmraid -> create soft raid from industry raid card format  ?

> Both should support isw to some degree.
> Intel are currently working with mdadm to make it provide full support for
> "IMSM" (Intel Matrix Storage Manager).  I don't know the exact relationship
> between 'isw' and 'IMSM' - maybe they are different names for the same thing.
ok

> If mdadm doesn't work for your isw arrays, and you want it to, then I suggest
> you report details about what is, or is not, happening.
My purpose is to improve archlinux startup detection of fakeraids
(mdadm + dmraid).

With mdadm everything works correctly without call to "mdadm -As"
With dmraid, no raid is created by udev rules, so we need to run
"dmraid -i -ay" at startup.

To test this kind of raid, i created a dmraid array in a vm. This
created me a /dev/mapper/isw_bfbjdbadhb_testF device.
call blkid on a disk member of this raid tell me this:
/dev/sde: TYPE="isw_raid_member"
and on "mdadm" created raid:
/dev/sdd: UUID="a974b525-993a-1481-f860-6471f3f120e1"
UUID_SUB="eb22aee2-b2ee-e56d-1008-44d52c63564d" LABEL="archipel:0"
TYPE="linux_raid_member"

This misled me because mdadm udev rules uses the output of blkid to
mount raids which have type "isw_raid_member".
What disturbs me is that mdadm cannot mount raid created by dmraid
with type isw_raid_member.

About outputs:
mdadm -I --verbose /dev/sde
mdadm: no RAID superblock on /dev/sde.

# mdadm --examine /dev/sde
/dev/sde:
          Magic : Intel Raid ISM Cfg Sig.
        Version : 1.1.00
    Orig Family : 5a8ed623
         Family : 5a8ed623
     Generation : 00000000
           UUID : ae2e9cd8:7fa43248:47c694a1:24990cbc
       Checksum : c23b6c88 correct
    MPB Sectors : 1
          Disks : 2
   RAID Devices : 1

  Disk00 Serial : 66faec8-9f5b237d
          State : active
             Id : 00040000
    Usable Size : 1019486 (497.88 MiB 521.98 MB)

[testF]:
           UUID : 6640a4cc:5faa1ce3:c1bff2b3:1093ca7d
     RAID Level : 1
        Members : 2
          Slots : [UU]
    Failed disk : none
      This Slot : 0
     Array Size : 1014446 (495.42 MiB 519.40 MB)
   Per Dev Size : 1014792 (495.59 MiB 519.57 MB)
  Sector Offset : 0
    Num Stripes : 3963
     Chunk Size : 64 KiB
       Reserved : 0
  Migrate State : idle
      Map State : normal
    Dirty State : clean

  Disk01 Serial : 0b540c6-4e527908
          State : active
             Id : 00050000
    Usable Size : 1019486 (497.88 MiB 521.98 MB)


Do not you think that dmraid should also ship an udev rules file to
mount the raid which can handle?

Regards,

-- 
Sébastien Luttringer
www.seblu.net
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