What is the status of RAID5 support with pdc (AMD SB850 Southbridge) hardware?

Heinz Mauelshagen heinzm at redhat.com
Fri Jan 14 13:02:57 UTC 2011

On Wed, 2011-01-12 at 23:16 +0200, Mantas Kriaučiūnas wrote:
> Hi dmraid developers,
> Thanks for improving free software :)


> I wonder what is the status of RAID5 support with pdc (AMD SB850 Southbridge) hardware?

dmraid is less about hardware, it's about RAID metadata support on
arbitrary hardware.

> AFAIK currently dmraid doesn't support RAID5 on pdc according to 
> 'dmraid -l |grep pdc' output:
> pdc    : Promise FastTrack (S,0,1,10)


> There are a lot of people, who are forced to use dual boot with nonfree 
> operating system, so we need more info about dmraid RAID5 support with 
> AMD SB850 hardware - look for example at these links:
> https://www.redhat.com/archives/ataraid-list/2011-January/msg00001.html
> http://ubuntuforums.org/archive/index.php/t-1531032.html
> https://bugzilla.novell.com/show_bug.cgi?id=634838
> (it seems there is important information at Suse bugzilla: when RAID5 is 
> created in BIOS then dmraid utility produces 'ERROR: pdc: RAID type 4 not 
> supported' during search of RAID partitions)

Yes, 4 is the metadata type code for RAID 5 in pdc.

> It would be nice to know where is the problem - in dmraid utility or 
> in kernel dm-raid45 module and when we could expect pdc RAID5 support?

For one the dmraid pdc metadata format handler in
lib/format/ataraid/pdc.[ch] needs an enhancement to support
the RAID5 mapping. Your links will help with that, thanks

For two, we need RAID5 support in custom kernels which will be given
ones the device-mapper RAID 4,5,6 target goes upstream for distros to
get it down.

The former isn't planned so far. RAID5 metadata samples are needed to
base such development on those. You can create them with "dmraid -rD",
tar them up bzip'ed and send them to me for further analysis.

The later is going to happen later this year.


> It seems I found "official" technical documentation about AMD SB850 fakeRAID 
> (after 6 hours searching) - see "RAIDBIOS_SB850_3.2.1540.31.zip" and
> "RAID Option ROM Implementation Guide V1.8.pdf" at 
> http://ftp.akl.lt/Linux/Baltix/devel/AMD-SB850-RAID-PROMISE/
> I've downloaded this documentaton from official AMD software page:
> http://wwwd.amd.com/AMD/SReleaseF.nsf/softwarepages/OptionROMs?OpenDocument
> (click at "More Info" near the text "AMD SB850 Chipset SATA RAID Option ROM v3.2.1540.31 - SATA RAID Option ROM for SB850 chipset.")
> Hope RAIDBIOS_SB850 binary files and documentation will be usefull for you 
> and you will find some time to implement RAID5 support or at least tell 
> me when we could expect RAID5 support for this fakeRAID.
> I can help you to test, but I don't know how to implement this, so, I'm 
> asking for help.
> Waiting for answer and good luck,
> --
> Mantas Kriaučiūnas	 Jabber ID: mantas at akl.lt 	 GPG ID: 43535BD5
> Developer of Baltix GNU/Linux OS - http://en.wikipedia.org/wiki/Baltix
> Public organization "Open Source for Lithuania" - www.akl.lt
> Use Baltix GNU/Linux OS - http://baltix.lt
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