Potential problem with software RAID?

grpprod · 09-20-2006, 05:07 AM

Hi all,
I have just installed a fresh CentOS 4.4 on a system with 4 IDE disks of 20GB each (not the same models, however, and therefore not the same size), utilizing software RAID. I have created /boot on a RAID1 using all 4 disks, one simple swap partition on each disk, and a RAID5 with all 4 disks using the remaining space (I did NOT create software RAID partitions with a size equal to the free size of the smaller disk). The system seems to work fine. I just noticed that fdisk reports an error (you can see it at the end of fdisk output) and I was wondering if I have to take it seriously. Any help will be appreciated.

Code:

# /sbin/fdisk -l

Disk /dev/hde: 20.0 GB, 20020396032 bytes
255 heads, 63 sectors/track, 2434 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/hde1   *           1          13      104391   fd  Linux raid autodetect
/dev/hde2              14          46      265072+  82  Linux swap
/dev/hde3              47        2434    19181610   fd  Linux raid autodetect

Disk /dev/hdf: 20.5 GB, 20547841536 bytes
255 heads, 63 sectors/track, 2498 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/hdf1   *           1          13      104391   fd  Linux raid autodetect
/dev/hdf2              14          46      265072+  82  Linux swap
/dev/hdf3              47        2498    19695690   fd  Linux raid autodetect

Disk /dev/hdg: 20.0 GB, 20020396032 bytes
255 heads, 63 sectors/track, 2434 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/hdg1   *           1          13      104391   fd  Linux raid autodetect
/dev/hdg2              14          46      265072+  82  Linux swap
/dev/hdg3              47        2434    19181610   fd  Linux raid autodetect

Disk /dev/hdh: 20.0 GB, 20020396032 bytes
255 heads, 63 sectors/track, 2434 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes

   Device Boot      Start         End      Blocks   Id  System
/dev/hdh1   *           1          13      104391   fd  Linux raid autodetect
/dev/hdh2              14          46      265072+  82  Linux swap
/dev/hdh3              47        2434    19181610   fd  Linux raid autodetect

Disk /dev/md0: 106 MB, 106823680 bytes
2 heads, 4 sectors/track, 26080 cylinders
Units = cylinders of 8 * 512 = 4096 bytes

    Device Boot      Start         End      Blocks   Id  System

Disk /dev/md1: 58.9 GB, 58924990464 bytes
2 heads, 4 sectors/track, 14385984 cylinders
Units = cylinders of 8 * 512 = 4096 bytes

Disk /dev/md1 doesn't contain a valid partition table

Code:

# cat /proc/mdstat
Personalities : [raid1] [raid5]
md1 : active raid5 hdh3[3] hdg3[2] hdf3[1] hde3[0]
      57543936 blocks level 5, 256k chunk, algorithm 2 [4/4] [UUUU]

md0 : active raid1 hdh1[3] hdg1[2] hdf1[1] hde1[0]
      104320 blocks [3/3] [UUU]

unused devices: <none>

WhatsHisName · 09-20-2006, 02:37 PM

That’s not an error message and it’s normal to get it.

Since you created a nonpartitionable software raid array, there is no partition table in md1.

grpprod · 09-20-2006, 03:52 PM

Thanks for the explanation, I appreciate it. I find it difficult to understand, though (I always need to understand what I am doing, and not just do it :-)). Where is the partition table stored in my case? Any good resource on this would be useful.