# dmraid, missing partitions [solved - not really]

## wildhorse

I have to deal with an nVidia MCP51 FakeRAID controller. Attached are two physical harddisks, configured as one logical mirrored disk. The devices for the individual disks (/dev/sd[ab]) exist. So do the devices for the two partitions on the disk (/dev/sd[ab][125]).

 *Quote:*   

> Disk /dev/sda: 160.0 GB, 160041885696 bytes
> 
> 255 heads, 63 sectors/track, 19457 cylinders
> 
> Units = cylinders of 16065 * 512 = 8225280 bytes
> ...

 

dmraid -ay found the nVidia FakeRAID system, and dmraid -s -f nvidia shows the set.

 *Quote:*   

> *** Active Set
> 
> name   : nvidia_jabdcdbd
> 
> size   : 312581760
> ...

 

But the devices for the partitions of the RAID set are missing!  :Confused: 

 *Quote:*   

> # ls -la /dev/mapper/ /dev/dm*
> 
> lrwxrwxrwx 1 root root 22 Jul 14 18:43 /dev/dm-0 -> mapper/nvidia_jabdcdbd
> 
> /dev/mapper/:
> ...

 

Fdisk finds the partitions on /dev/dm-0, though. I noticed that fdisk reports 1024 bytes less for /dev/dm-0 than for /dev/sd[ab]. Not sure if that matters (guess these are the sectors used to store the RAID configuration).

 *Quote:*   

> Disk /dev/dm-0: 160.0 GB, 160041884672 bytes
> 
> 255 heads, 63 sectors/track, 19457 cylinders
> 
> Units = cylinders of 16065 * 512 = 8225280 bytes
> ...

 

No point in trying to mount something that is not there. Why does the kernel not discover the partitions of the RAID set?

 *Quote:*   

> 2.6.29-gentoo-r5 x86_64 AMD Athlon(tm) 64 X2 Dual Core Processor 4800+

 Last edited by wildhorse on Fri Jul 17, 2009 7:36 am; edited 1 time in total

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## DONAHUE

http://www.gentoo-wiki.info/HOWTO_Install_Gentoo_with_NVRAID_using_dmraid#Building_the_Kernel is dated but looks helpful.

You need an initramfs, genkernel --dmraid all may be easy way for you.

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## wildhorse

My kernel is fine. And since I am not trying to boot from the RAID set and its NTFS (MS Windows) file systems, I doubt that I really need initramfs. Neither do I want genkernel.

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## wildhorse

In order to check what dmraid would find, I deactivated the RAID set with dmraid -an. Then I used dmraid -ay -vvv -d and expected something that would indicate what goes wrong. However, dmraid now found the two partitions and added them to /dev/mapper/! Before, I only added an entry in /etc/dmtab for the entire RAID set (not the partitions), which  I got from dmsetup table after the first dmraid -ay. The kernel and the other software remained untouched. As far as I can see from the documentation, dmraid should have found the partitions the first time and I am not sure if the entry in /etc/dmtab made a difference.

After a reboot, the partitions are still there. That is good. But somehow the whole dmraid solution does not look too trustworthy. On the long run I will try to replace this nVidia FakeRAID with a true hardware RAID solution.

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## John R. Graham

Are these PATA or SATA drives?

- John

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## wildhorse

 *john_r_graham wrote:*   

> Are these PATA or SATA drives?
> 
> - John

 

SATA

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## John R. Graham

Oh, okay.  Given the size, I had guessed PATA.  I was going to suggest a really nice old PATA RAID card made by Adaptec that has good Linux support (and that I have personal experience with).  I am a strong believer in using generation-before-last server technology to produce high-performance, highly reliable home servers and desktops.    :Wink: 

- John

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## wildhorse

Sure, there are plenty of good alternatives to those damn nVidia FakeRAID interfaces, even for PATA. But in this particular case I cannot change the configuration.

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## cengique

I had a similar problem with 'dmraid -ay' not finding the partitions although it finds the nvidia swraid properly.

It turns out, it was also trying to get the Intel swraid after that and was choking on that probably because it was already handled by mdadm.

So, when I pushed dmraid only to process the nvidia swraid with:

```
dmraid -ay -f nvidia
```

And, it worked!

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