Hi Lars,
At 11:56 PM 26/03/2003 +0100, Lars Marowsky-Bree wrote:
[..]
>We do parse device specific information in order to auto-configure the md
>multipath at setup time. After that, magic is on disk...
>
> > does one now need to add logic into the kernel to provide some multipathing
> > for HDS disks?
>
>Topology discovery is user-space! It does not need to live in the kernel.
i think we're agreeing on the same thing here!
yes, i believe topology discovery should only belong in userspace.
i believe it should be in userspace for both (a) setup and (b) at
kernel-boot-time
likewise, i believe policy of deciding what mix of i/o's to put down
different paths also belongs in userspace.
this could take the form of a daemon that frequently looks up statistics
from the kernel (e.g. average latency per target), and uses that
information in conjunction with some 'policy' to tweak what paths are used.
but i definitely don't think that the kernel should make any wide-ranging
decisions about multiple paths, except beyond something like "deviceA has
disappeared. i know that deviceB is an alternate path, so will swing all
outstanding i/o plugged into A to B".
cheers,
lincoln.
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This archive was generated by hypermail 2b29 : Mon Mar 31 2003 - 22:00:26 EST