RE: [Xen-devel] Getting xen to recognise large disks

["Ian Pratt" <m+Ian.Pratt@xxxxxxxxxxxx>]

>  - 8x500GB SATA drives combined as /dev/md2 (RAID6)
>  - /dev/md2 designated an LVM PV
>  - Volume Group vg_media created using /dev/md2
>  - Logical Volume lv_media created in vg_media
>  - ext3 filesystem created on lv_media
> 
> 
> I'm using the following disk config in my xen config file:
> 
> disk = [ 'phy:vg_host/lv_slim,xvda,w',
>          'phy:vg_media/lv_media,xvdb,w', ]
> 
> 
> However, /dev/xvdb is not appearing as the correct size in the DomU
guest:
> 
> >From /proc/partitions:
> 
> major minor  #blocks  name
>  202    16  782819328 xvdb
> 
> When I look at the same partition in the host, I see this:
> major minor  #blocks  name
>    9     2 2930303616 md2
> 
> There appears to be a problem in passing the size of the device to the
> DomU guest.

Hmm, 2930303616 - 2^31 = 782819968

Argh -- I can see the problem: see the connect function in blkfront.c.

Fortunately, it can be fixed without an interface change. Just change
'sectors' from an unsigned long to a blkif_sector_t and update the
xenbus_gather to use:  "sectors", "%llu", &sectors 

You'll also need to edit the xenbus_printf (to %llu) in the connect
function in blkback.c too.

Please post a patch!

Thanks,
Ian







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