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Old 03-16-2008, 06:42 PM   #1
chakkerz
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Registered: Dec 2002
Location: Brisbane, Australia
Distribution: RedHat (RHEL, FC, CentOS), openSuSE, Mac OS X
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device mapper / multipath creating extra device, won't let me talk to the one i want


Hello there

I'm using CentOS 5.1 (as well as RHEL 5.1). Since my more immediate problem is with CentOS, and not my production environment (RHEL) i figured i'd try here, rather than RedHat. Google doesn't seem to give me anything useful and Red Hat's documentation on the subject (http://www.redhat.com/docs/manuals/e...ath/index.html) is not particularly useful either.

I've got two RAID provided disk groups /sda and /sdb which i've blacklisted in /etc/multipath.conf so that they don't show up. So remaining visible are /sdc and /sdd which are my HBAs. However i don't believe the problem is with multipathd.

I believe device mapper is what's at fault alas i can't find much about actually configuring IT itself.

when my system has started i get the following output from `fdisk -l`

Code:
root@fact /]# fdisk -l

Disk /dev/sda: 146.1 GB, 146163105792 bytes
255 heads, 63 sectors/track, 17769 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sda1   *           1          16      128488+  83  Linux
/dev/sda2              17        1060     8385930   83  Linux
/dev/sda3            1061        2104     8385930   83  Linux
/dev/sda4            2105       17769   125829112+   5  Extended
/dev/sda5            2105        3148     8385898+  83  Linux
/dev/sda6            3149        3670     4192933+  83  Linux
/dev/sda7            3671        4192     4192933+  83  Linux
/dev/sda8            4193        4714     4192933+  83  Linux
/dev/sda9            4715        4968     2040223+  82  Linux swap / Solaris
/dev/sda10           4969       17769   102824001   83  Linux

Disk /dev/sdb: 146.1 GB, 146163105792 bytes
255 heads, 63 sectors/track, 17769 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdb1   *           1       17769   142729461   83  Linux

Disk /dev/sdc: 322.1 GB, 322122547200 bytes
255 heads, 63 sectors/track, 39162 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdc1               1       39162   314568733+  83  Linux

Disk /dev/sdd: 322.1 GB, 322122547200 bytes
255 heads, 63 sectors/track, 39162 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/sdd1               1       39162   314568733+  83  Linux

Disk /dev/dm-0: 322.1 GB, 322122547200 bytes
255 heads, 63 sectors/track, 39162 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

     Device Boot      Start         End      Blocks   Id  System
/dev/dm-0p1               1       39162   314568733+  83  Linux

Disk /dev/dm-1: 322.1 GB, 322118383104 bytes
255 heads, 63 sectors/track, 39161 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

Disk /dev/dm-1 doesn't contain a valid partition table

/sda and /sdb, no issue, /sdc and /sdd with their single underlying partition, matching in size (and in fact layout) /dev/dm-0 the amalgamation of the two, with it's amalgamated /dev/dm-0p1 . and then there is /dev/dm-1 which is >just< smaller than sdc, sdd and dm-0 .

Until last week, i found this odd but accepted it, because although i could not interact with dm-0 OR dm-0p1 i could interact with dm-1 which worked swell. But now that i have a basically working system, i would like to tie up loose ends.

what is dm-1 and why don't i have a /dev/dm-0p1 ? Any documentation i find doesn't really go beyond setting up dm, and never goes into interacting with the device, beyond that you end up using it (thus adding to my confusion).

Does anyone have any familiarity with this, and is thus able to help me out?

Please?

cheers, chakkerz
 
Old 03-16-2008, 06:52 PM   #2
chakkerz
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Registered: Dec 2002
Location: Brisbane, Australia
Distribution: RedHat (RHEL, FC, CentOS), openSuSE, Mac OS X
Posts: 653

Original Poster
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Ok, gumby issue:

[root@fact ~]# dmsetup ls
360060e80045a000000005a0000000221p1 (253, 1)
360060e80045a000000005a0000000221 (253, 0)
[root@fact dev]# ls -l dm-*
brw-rw---- 1 root root 253, 0 Mar 17 08:37 dm-0
brw-rw---- 1 root root 253, 1 Mar 17 08:37 dm-1

So i guess, that explains that ... sorry for that dumb moment. Hope i didn't waste too much of anyone's time

chakkerz
 
  


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