Re: [Xen-users] Extending a disk attached by iscsi

["Austin S. Hemmelgarn" <ahferroin7@xxxxxxxxx>]

On 2016-11-29 07:28, Austin S. Hemmelgarn wrote:
> On 2016-11-28 17:26, Lang, Adam wrote:
> > Hello,
> >
> >
> >
> > I inherited an old Xen environment with one VM remaining that we need to
> > use for the foreseeable future.
> >
> > xen_caps               : xen-3.0-x86_64 xen-3.0-x86_32p
> >
> >
> >
> > A disk for the VM is mapped via iscsi on a Dell Powervault for 2
> > terrabytes.  I increased the virtual capacity of the mapping on the
> > powervault to over 3 terrabytes, but the actual VM still only recognizes
> > 2 TB.
> >
> >
> >
> > I can’t seem to find the appropriate way to have Xen recognize the
> > larger capacity and the only Xen/iSCSI docs I see online are about newer
> > Citrix oriented platforms.
> >
> >
> >
> > If anyone can share ideas or where I can look, it would be appreciated.
> This really depends on how the disk is actually attached.  If you're
> using regular Xen then Xen itself is not handling the iSCSI stuff
> (XenServer does though, which is why you see the Citrix stuff when
> searching).  Assuming that the guest isn't mapping the device itself
> (which may be more efficient in some cases), then:
> * For a HVM domain, it's the device-model (QEMU) doing the handling, so
> you'd need to look at that.
> * For a PV domain, it's handled by the Domain-0 OS (so for this, check
> the docs for whatever you're using for your Domain-0).
>
> In either case, your guest OS may be limiting things too (2TiB - 1 byte
> is a common storage stack limitation because that happens to be roughly
> 2^48 (and many older systems only support 48-bit LBA)).  If the VM is
> older than a few years, this is actually what I would suspect first, not
> some other configuration issue.
Realized almost immediately after I sent this that I meant 512 * (2^32), 
not 2^48, and a 32-bit max sector count, not 48-bit LBA....
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