Red Hat Bugzilla – Bug 216555
Virtual disk size wraps around at 2 TB mark
Last modified: 2009-12-14 15:39:09 EST
Description of problem:
If I create a virtual disk (either a file, or block device backed) in the dom0
host with a size of 5 TB, and export this to a guest DomU, the domu will only
see it as being 1 TB in size. It looks as if the Xen virtual disk driver is
wrapping around at the 2 TB mark.
Version-Release number of selected component (if applicable):
Always (on 32-bit)
Steps to Reproduce:
1. Create an block device 7 TB in size
2. Export this to the DomU in the guest config file
3. Look at /proc/partitions inside the guest kernel
4. Look at /proc/partitions in the dom0 host kernel
The #blocks column for the disk is different in DomU & Dom0
The #blocks seen in DomU matches #blocks seen in Dom0
The same problem occurs for file backed virtual disks on 32-bit host/guest.
There is no problem on 64-bit kernels - I have exported disks as large as 15 PB
to the guest.
This is all testing with paravirt guests. Not verified if fully virt guests have
any issues yet.
Post from Ian upstream suggests 32-bit wraparound in blkfront driver
I'm seeing the same thing.
I'm trying to make a 2.73TB ext3 FS available to a DomU guest.
It's docmented here:
Patch committed in xen-unstable.hg
I have tested the patch listed in comment #2 and confirmed it fixes operation of
file: and phy: backed disks > 2 TB in size. It does not, however, fix tap:aio:
Created attachment 141844 [details]
Patch for blktap based disks
This additional patch fixes blktap based disks which are > 2TB
Woohoo! I installed the patched kernel & xen RPMS this morning and I can now see
m y large partition correctly in the DomU guest.
Thanks for the quick fix and help rebuilding the RPMS.
Can I get an update on the status of this issue?
i.e. has the patch been applied upstream yet? When will we see RPMS with this fixed?
change QA contact
This report targets FC6, which is now end-of-life.
Please re-test against Fedora 7 or later, and if the issue persists, open a new bug.