Partition not showing under /dev

LightUnsigned · 09-19-2009, 01:56 AM

I have been having some weird issues with one of my hard drives. It's a SATA drive, with a single partition, and is part of a RAID-5 array.

The drive itself shows up fine in /dev (its /dev/sdd). However, its ext3 partition (/dev/sdd1) does not show up under /dev at all. Running "fdisk /dev/sdd" and looking at the partition table shows:

Code:

Disk /dev/sdd: 1000.2 GB, 1000204886016 bytes
255 heads, 63 sectors/track, 121601 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes
Disk identifier: 0xf2567fad

   Device Boot      Start         End      Blocks   Id  System
/dev/sdd1               1      121601   976760032   83  Linux

So the partition is indeed there.

Deleting the partition, re-creating the partition and rewriting the partition table makes it show up in /dev as /dev/sdd1. However, as soon as I reboot, it is gone again.

What could be causing this? Is there a way to force linux to (perhaps rescan/repopulate) /dev?

I am using Arch Linux with kernel 2.6.30 if thats any help

ongte · 09-19-2009, 11:14 PM

If the drive /dev/sdd is part of an array, you shouldn't need any partitions on it. The RAID will take care of it. You should not be interacting with it's partitions or data directly. You should be working with the virtual disk instead. If this is Linux software raid, you need to manage it with mdadm and the device /dev/md0.

LightUnsigned · 09-19-2009, 11:26 PM

My RAID device (/dev/md0) is supposed to be made up of /sdb/sdb1 /dev/sdc1 and /dev/sdd1 (this worked fine when /dev/sdd1 was recognised by the system)

Code:

[root@bourbon ~]# cat /proc/mdstat
Personalities : [raid6] [raid5] [raid4] 
md0 : active raid5 sdb1[0] sdc1[1]
      1953519872 blocks level 5, 64k chunk, algorithm 2 [3/2] [UU_]
      
unused devices: <none>

my ARRAY line in /etc/mdadm.conf shows:

Code:

ARRAY /dev/md0 level=raid5 num-devices=3 metadata=0.90 spares=1 UUID=5d4e8f42:5d294e29:f05cfb20:afc38780

In order to re-add /dev/sdd1 to the array, it needs to be recognised by the system. For some reason it isnt

ongte · 09-19-2009, 11:51 PM

First of all, if you were using the full drive, you did not need to create partitions on them b4 creating the RAID array. You should have just used the raw empty disks.

With your current setup, you will need to create a partition on the disk, changed it's type to 'fd' (linux raid auto) then add it back into the array. Remember to run partprobe to refresh the kernel.

LightUnsigned · 09-20-2009, 02:29 AM

Ok, I did that and it showed up in /dev right away. I added the disk back into the array and its rebuilding now.

Once its done, I'll restart and see if it comes back up properly

Thanks for your help