fakeraid/dmraid on intel matrix RAID-0 array

Phillip Susi psusi at cfl.rr.com
Wed Jul 16 21:47:25 UTC 2008

Greg Watson wrote:
> I've been following these guides:
> http://help.ubuntu.com/community/FakeRaidHowto
> which lead me to this page:
> https://help.ubuntu.com/community/FakeRaidDebug
> I have followed the guide, located the exact Array information sectors.


> Before patching, dmraid told me this:
> Code:
> ERROR: isw: Error finding disk table slot for /dev/sdb
> ERROR: isw: Error finding disk table slot for /dev/sda
> No RAID disks
> I then tried patching dmraid code per the guide. So the dd copied the last
> 1024 bytes, so 1024 / 512 (per sector) = 2.
> After patching #define ISW_CONFIGOFFSETS in the code (isw.h) and
> recompiling, I only get.

The patching part of the guide is for pdc controllers, not Intel, since 
pdc likes to throw their metadata in all sorts of odd offsets, but Intel 
always goes with 2 sectors from the end.  The error does not indicate 
that it can't find the metadata, but that there is a problem with the 
metadata it found where it can't find the part that specifically 
describes that disk.

This is the result of a bug I mentioned in a recent thread entitled "Why 
are spaces removed from the disk serial number?" in which I point out 
that dmraid removes whitespace from the disk serial number before trying 
to compare it with the serial number recorded in the metadata, which no 
longer matches since it still has the whitespace.  I never did get an 
answer about why the whitespace is removed, and if that removal can be 
disabled to fix this problem.

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