Monday, 20 January 2014

Re: [RFC/CFT] Trusty work for dmraid

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On 1/20/2014 7:03 AM, Stefan Bader wrote:
> I have prepared changes for both[2] which did work for IMSM (before
> I disabled support) and a RAID5 I had there. Currently there would
> only be one drawback which is that cases which store meta-data at
> the beginning of a disk and data after that would not work. But I
> am not sure whether there are cases out there that work like this.

What do you mean? isw always stores its meta data at the end of the disk.

> So practically the only setups to worry are NVidia controllers
> supporting RAID5 and those using DDF1 using RAID4 or 5. Are there
> people out there which have BIOS-/fakeRAID configs enabled for
> RAID4 or 5 and currently use dmraid to set those up under Linux?

DDF1 may be fairly common on servers since this is the usual format
used by server class fakeraid cards, and servers are typically set up
using raid5.

> One alternative option would be to check whether mdadm DDF support
> also includes everything that dmraid did. At least a quick test
> with a ddf1 RAID5 which I did set up using mdadm seems to be found
> by dmraid scanning, too. That option would leave us only with
> NVidia controllers depend on dmraid RAID5.

Last I saw on the linux-raid mailing list they were still shaking a
few bugs out of the ddf support in mdadm. nvidia controllers seem to
mainly have been used in enthusiast/gamer/workstation desktop boards
where raid0 is far more likely than raid5.

> Btw, to make mdadm automatically add the IMSM RAID I have to add
> the following line to /lib/udev/rules.d/64-md-raid.rules:
>
> # handle potential components of arrays (the ones supported by md)
> ENV{ID_FS_TYPE}=="linux_raid_member", GOTO="md_inc"
> +ENV{ID_FS_TYPE}=="isw_raid_member", GOTO="md_inc"
> GOTO="md_inc_skip"

What about making sure that dmraid *isn't* used to activate the array?


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