Help understanding how drives/arrays are detected
Hi all,
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: Code:
[root@db2 backups]# grep sdc /var/log/dmesg 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? Thank you |
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.
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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 Code:
[root@db2 ~]# df -h I accept that sdc is how the physical enclosure is seen by the OS, but why is the partition dm-0 and not sdc1? Thank you. Elliot |
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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