*** Announcement: dmraid 1.0.0-rc1 available at http://people.redhat.com:~heinzm/sw/dmraid

[Heinz Mauelshagen]

On Tue, Jul 06, 2004 at 04:52:27PM -0400, Jack Howarth wrote:
> Heinz,
>    I am confused about the exact purpose of the dmraid utility.
> Reading the documentation it seems able to read metadata for
> RAID partitions that use the closed source Promise raid driver
> under Linux 2.4.

Yes (see README), validated in my test bed with the FastTrak TX2000.

dmraid is aiming to fill the gap between the IDE drivers available
for many ATARAID cards in Linux 2.6 (which *don't* cover RAID) and
accessing the RAID sets on the drives attached, by activating
respective Mapped Devices using the Device-Mapper runtime of the Linux
2.6 kernel.

In order to achive this, access to the vendor (eg, Promise) specific
metadata is necessary.


> Assuming that is the case, will dmraid allow
> us to access these RAID partitions (where the Promise chipset
> is set in RAID rather than ultra mode) under Linux 2.6?

AFAIK, and I admit I don't know them all ;), most chipsets on
ATARAID cards are special (multi) IDE controllers and the whole RAID mapping
business is done in (proprietary) SW.

IOW: the Linux ATARAID chipset drivers allow dmraid to access all sectors
on the drives in order to retrieve the BIOS written metadata and make
up the mappings for Device-Mapper to activate access.

> Also
> will we be able use use such partitions as the boot and root
> partitions for the system?

Yes, that's the plan.

It can run in early boot environments before root and friends get accessed
and activate the ATARAID sets at that early stage so that access to those
is possible.
dmraid 1.0.0-rc1 is linkable to dietlibc making it a ~80K executable suitable
for such space constraints. Will see if it is feasable to link it to klibc
making it even smaller.
BTW: linked shared to the libdmraid, the executable is ~10K only.


>    I ask because currently I have been setting up machines
> with two identical SATA drives attached to the Promise chipset
> (running in Ultra mode rather than DMA mode) and using
> software RAID-1 partitions created in DiskDruid/Anaconda under
> the FC2 installer. While this is fine for Linux only machines,
> it would be nice to have the option of using the Promise RAID
> chipset in RAID mode for dual boot machine so that the Windows
> partition could use the Promise RAID drivers.

That should be possible with dmraid (not tested), because it leaves
the metadata intact, which got written by the Promise BIOS.
This is the very same metadata which is used by Windows Promise RAID
driver as well.

You're welcome to be a tester for such a dual boot config ;)

> Currently I would
> have to setup some sort of software RAID under Windows since
> I have to turn the Promise RAID chipset to Ultra mode so that
> I can use the promise-sata driver under Linux 2.6.

That change is about setting the IDE chipset to a mode so that the Linux
IDE driver can handle it.
Should have no influence on metadata access which is important for dmraid
and the Windows Promise RAID driver.

Just try to run dmraid on Linux and see if it is able to discover your
Promise RAID devices and set(s).
Use "dmraid -r" and "dmraid -s", which are both read-only.
See "man dmraid" for details.

>    Thanks in advance for any clarifications.
>                          Jack
> 
> 
> -- 
> fedora-list mailing list
> fedora-list at redhat.com
> To unsubscribe: http://www.redhat.com/mailman/listinfo/fedora-list

-- 

Regards,
Heinz    -- The LVM Guy --

=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-

Heinz Mauelshagen                                 Red Hat GmbH
Consulting Development Engineer                   Am Sonnenhang 11
                                                  56242 Marienrachdorf
                                                  Germany
Mauelshagen at RedHat.com                            +49 2626 141200
                                                       FAX 924446
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-