Re: KVM incompatible with multipath?

[Anthony Liguori <anthony@codemonkey.ws>]

infernix wrote:
> Hi,
>
> I've got an Equallogic iSCSI box with 3x1GBit nics on my storage
> network. I also have a server with 4 nics of which 3 are connected to
> the storage network with 3x1GBit.
>
> On this host, open-iscsi is running and connecting to the SAN over 3 
> interfaces. I'm seeing /dev/sdb, sdc and sdd, which are all the same 
> harddisk (same WWID).
>
> With multipath I combine them to one disk to get a nice boost in
> performance. This works perfectly fine (and very speedy) on the host.
> Relevant multipath.conf data:
>
> device {
>  vendor "EQLOGIC"
>  product "100E-00"
>  path_grouping_policy multibus
>  getuid_callout "/lib/udev/scsi_id -g -u -s /block/%n"
>  features "1 queue_if_no_path"
>  path_checker readsector0
>  failback immediate
>  path_selector "round-robin 0"
>  rr_weight uniform
>  rr_min_io 128
> }
>
> The problem with KVM (version 87) is that KVM cannot make use of the
> multipath device in /dev/mapper.
>
> If I boot a debootstrapped Debian Lenny KVM guest and configure it with
> -hda /dev/mapper/my-multipathed-iscsi-disk, I cannot mount the root
> partition. It'll complain about "Invalid target".

How do you get the disk image onto /dev/mapper/my-multipathed-iscsi-disk?

You need to create a partition table and setup grub in order to be able 
to use something as -hda.  You don't get that automatically with 
debootstrap.

Regards,

Anthony Liguori