Question about RAID set names

Jane Liu janliu at
Wed Sep 22 20:50:46 UTC 2004


I'm working on a metadata handler for dmraid, and I'm a bit confused
about the construction of RAID set names. Does the name need to stay the
same for the lifetime of the array? Does it need to be unique? 

And what's the relationship between /dev/mapper and /dev/dm-* devices? I
noticed that when an array, say, /dev/mapper/nvraid_abcdefgh is
activated, a /dev/dm-0 also appears. I can run fdisk and mkfs, etc. on
both of them. After reboot, /dev/mapper/nvraid_abcdefgh still exists but
cannot be opened, where as /dev/dm-0 no longer exists. After running
dmraid -ay, /dev/dm-0 appears again. If I change the RAID set name to
"nvraid_blah", then running "dmraid -ay" creates /dev/mapper/nvraid_blah
as well as /dev/dm-0. So it seems that /dev/dm-* enumeration is
independent of the RAID set names. Does that mean it's OK to change the
RAID set name during the lifetime of the set? 

Thanks in advance for any help.


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