Re: *** Announcement: dmraid 1.0.0-rc1 available at http://people.redhat.com:~heinzm/sw/dmraid
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. 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? Also will we be able use use such partitions as the boot and root partitions for the system? 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. 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. Thanks in advance for any clarifications. Jack
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
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Heinz Mauelshagen -
Jack Howarth