On Sun, Apr 17, 2011 at 5:38 PM, NeilBrown <neilb@xxxxxxx> wrote: > On Fri, 15 Apr 2011 16:15:50 +0200 Seblu <seblu@xxxxxxxxx> wrote: > >> On Tue, Apr 5, 2011 at 8:20 AM, NeilBrown <neilb@xxxxxxx> wrote: >> > On Sun, 3 Apr 2011 18:03:50 +0200 Seblu <seblu@xxxxxxxxx> wrote: >> > >> >> Hello, >> >> >> >> In the following commit, udev rules load isw_raid (fakeraid). From my >> >> test, this doesnt work. I have to call dmraid to have something >> >> working. >> >> http://neil.brown.name/git?p=mdadm;a=commit;h=475a01b8bce8575dd1b2ab6495e65e854702ac0e >> >> >> >> isw_raid is only fakeraid devices? mdadm is able to mount fakeraid partition? >> >> >> > >> > I'm sorry but I cannot parse those questions successfully so I'm not sure >> > what you are asking. >> >> Hello Neil, >> >> in my previous mail, i used word fakeraid about raid created with >> dmraid and i used softraid about raid created with mdadm. it was not >> clear. >> >> So my question was about compatibily. Raids created by dmraid can be >> assembled with mdadm and vice versa? >> >> > Both dmraid and mdadm can manage some 'fakeraid' arrays. dmraid supports a >> > wider variety. mdadm supports raid1 and raid5 more completely than dmraid >> > does. >> mdadm -> create soft raid for linux (now there is new format: ddf and imsm) ? >> dmraid -> create soft raid from industry raid card format ? > > No, it isn't that simple. > > dmraid uses the 'dm' kernel module. mdadm uses the 'md' kernel module. > > As such dmraid doesn't support RAID5 (yet) and doesn't support RAID1 very > well. > mdadm supports both of these well, but doesn't support the same range of > "industry raid card formats". > > There is a growing amount of overlap. > >> >> > Both should support isw to some degree. >> > Intel are currently working with mdadm to make it provide full support for >> > "IMSM" (Intel Matrix Storage Manager). I don't know the exact relationship >> > between 'isw' and 'IMSM' - maybe they are different names for the same thing. >> ok >> >> > If mdadm doesn't work for your isw arrays, and you want it to, then I suggest >> > you report details about what is, or is not, happening. >> My purpose is to improve archlinux startup detection of fakeraids >> (mdadm + dmraid). >> >> With mdadm everything works correctly without call to "mdadm -As" >> With dmraid, no raid is created by udev rules, so we need to run >> "dmraid -i -ay" at startup. >> >> To test this kind of raid, i created a dmraid array in a vm. This >> created me a /dev/mapper/isw_bfbjdbadhb_testF device. >> call blkid on a disk member of this raid tell me this: >> /dev/sde: TYPE="isw_raid_member" >> and on "mdadm" created raid: >> /dev/sdd: UUID="a974b525-993a-1481-f860-6471f3f120e1" >> UUID_SUB="eb22aee2-b2ee-e56d-1008-44d52c63564d" LABEL="archipel:0" >> TYPE="linux_raid_member" >> >> This misled me because mdadm udev rules uses the output of blkid to >> mount raids which have type "isw_raid_member". >> What disturbs me is that mdadm cannot mount raid created by dmraid >> with type isw_raid_member. >> >> About outputs: >> mdadm -I --verbose /dev/sde >> mdadm: no RAID superblock on /dev/sde. Seblu can you verify that: export IMSM_NO_PLATFORM=1 mdadm -E /dev/sde finds no superblock? It may be that dmraid has laid down something incompatible. > As has been mentioned elsewhere, mdadm only recognised IMSM arrays on > machines with IMSM hardware. I'm not entirely happy about this and may well > change it. I have trouble answering the "least surprise" question in this area. Is it more surprising to go into your BIOS, explicitly turn off raid support and still see raid devices showing up? Or is it more surprising to take a raid array from a raid enabled system to raid disabled system and wonder why things won't assemble? For safety I think it is better if mdadm not perform operations that might be incompatible with the platform option-rom. But if you need to recover to a usb attached drive, or some other platform-incompatible configuration, you can use the environment variable in a pinch. -- Dan -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
