Help understanding how drives/arrays are detected
I've made such a hash of configuring an external RAID enclosure on a RHEL6 box, I've got to the point where I don't know how I actually got to where I am now!
Anyway, I think I have it working now, but I would like some help understanding something.
In my very limited experience of installing disks under linux before, I have just seen them as /dev/sda, /dev/sdb etc, then created partitions which appear as /dev/sda1, /dev/sda2 etc.
Dmesg shows my device as sdc:
Now I understand this is something to do with the drive mapper, but that's all I know! :confused:
I have been able to format and use it so I guess it's working okay, but could a kind soul please explain, or speculate, why my device has appeared as /dev/dm-0 and not /dev/sdc1?
A raid partition is a virtual device, not a physical one. /dev/sdc points to the physical drive, while /dev/dm-0 is the virtual partition that combines the space of multiple discs.
Hi David the H,
Thank you for your reply, but that doesn't seem to satisfy what I am seeing. Or I am misinterpreting your answer.
My server consists of:
2 x internal HDDs (RAID1) = sda
8 x internal HDDs (RAID10) = sdb
12 x HDDs (external enclosure) (RAID10) = sdc
I accept that sdc is how the physical enclosure is seen by the OS, but why is the partition dm-0 and not sdc1?
Could you post the entire configuration?
Like output of "fdisk -l", "cat /etc/fstab", raid configuration I guess can be shown by mdadm in some way but it's a long time since I used it so don't really know.
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