[Evms-devel] EVMS volumes and raw I/O.

[John M. <jm...@sa...>]

Another question, while I'm at it:

I am setting up some machines to act as UML (User Mode Linux) hosts
using EVMS-managed volumes as the storage for their virtual drives.
Specifically, I have an LVM2 container on top of a Raid1 mirror,
and allocate the UML virtual drive volumes from that container.

What I'd like to try to do is bind the UML volumes as raw devices
using the Linux 'raw' command in order to hopefully improve
filesystem I/O performance in the UML guests.

First, does raw I/O even work for EVMS and/or device-mapper mapped
volumes?  Second, if it "works", does it still provide direct I/O
between the process and the physical controller?  I suppose I could
just try it out, but I'd be interested in knowing if it will buy
me any performance gains even if it does appear to run.

Thanks.
--
John Marco / Samba Holdings, Inc. / Albuquerque, NM