kern/171415: [zfs] zfs recv fails with " cannot receive incremental stream: invalid backup stream"

[Martin Birgmeier]

Good news...

I upgraded the FreeBSD head running in the virtual machine v903 to
r241507, with the goal to see whether the problem described has been
fixed in the meantime. (The server, hal, is still at 8.2 release.)

In addition, instead of using iSCSI to make disk{31..36}p4 from hal
appear in v903, I attached them as devices directly using VirtualBox
(all to one and the same virtual SATA controller). Now the test worked,
and I could successfully receive the backup stream. I even made an md5
comparison of all the files in the received file system (> 53000), which
went through without a single difference. Very good!

What was left was testing with the original test setup again, i.e.,
using iSCSI. Unfortunately, this still fails in the same way, so it
seems that something with iscontrol or istgt is broken.

On a hunch, I'd say it is iscontrol, simply because I assume that on the
server side (ports/net/istgt) there is not that much that can break, it
being a userland application, whereas iscontrol is a kernel module
hooking into the SCSI subsystem.

Therefore, this defect should possibly be reclassified and instead of
[zfs] have some other sticker applied.

Regards,

Martin

p.s. I am using istgt also with disk images of MS Windows XP
installations, exporting them to remotely running VirtualBox instances
without any issues - to me a hint that istgt is quite o.k. Of course,
the zfs scenario uses 6 iSCSI targets at the same time, whereas the XP
emulation uses only one, so maybe either istgt or iscontrol have
problems with multiple connections/instances.