[dm-devel] kernel 2.6 biosraid via device mapper - partition support

[Don Mulvey]

>i just started to investigate how biosraid support for the HPT37X
>IDE-chipsets can be implemented in the 2.6 kernel. implementing the
>basic raid levels (0, 1, 0+1, JBOD) seems to be pretty straight forward.
>this can be done by reading the raid signatures of the disks and then
>pipeing the configuration through dmsetup or using the libdevmapper
>library directly. what bothers me is the partition support. the number
>of minor device nodes that are registered per mapped block device is 1.
>this means that there is no way that the kernel does the
>partition-handling by itself. the alternative is to do the partition
>scanning in userspace and to use another device mapper layer to create
>the partition device nodes. it appears that this was already suggested
>by Christophe Varoqui ( http://lwn.net/Articles/13958/ ) but this
>project is now idle. this also has the disadvantage that any changes in
>the partitioning of the raid volume (e.g. by using *fdisk, distribution
>installers, ...) require a manual re-invocation of the biosraid setup
>tool. plus the whole code under linux/fs/partitions/... has to be
>duplicated so that not only the dos partitioning scheme is supported,
>but also BSD slices, x86 solaris, windows dynamic disks, ...

Sounds like you should look at the EVMS activate command.  EVMS can already
recognize and activate/reactivate: os/2, dos, bsd (compatible and
dedicated), solarisx86(embedded), unixware(embedded), 390 (cdl,ldl,cms),
mac, cluster and bbr partitions throught its device mapper interface.

-Don