At Tue, 20 Apr 2021 16:53:58 -0700, "Greg A. Woods" <wo...@planix.ca> wrote: Subject: Re: Xen FreeBSD domU block I/O problem on -current only affects reads > 1024 bytes > > With the gracious help of RVP <r...@sdf.org> I have been able to identify > better what is actually going wrong with FreeBSD's access to NetBSD dom0 > xbdback(4) storage. > > It seems that in certain circumstances (e.g. in newfs and the test > program) whenever FreeBSD issues a read of more than 1024 bytes only the > first 1024 bytes are correct -- the rest of the bytes returned come from > somewhere else on the disk, which appears to be starting at six(6) > sectors after where they were supposed to have come from. Note that > this corresponds to exactly 4096 bytes offset from the beginning of the > read.
Reviving this old thread with some new info....
It seems ZFS either doesn't issue large read requests, and/or it works
around the problem in some other way.
With the help of a custom FreeBSD kernel with ZFS compiled in, and
booting it as a PVH domU kernel, and with the new(ish) FreeBSD (14.0)
way of installing with a ZFS root, I have a couple of domUs running just
fine now, one even recovered old zpools on the machine where I first
experienced this problem!
As soon as possible, especially if I can dredge up another test server,
I'll test plain UFS again with a NetBSD 10.0_RC2 kernel as dom0.
--
Greg A. Woods <gwo...@acm.org>
Kelowna, BC +1 250 762-7675 RoboHack <wo...@robohack.ca>
Planix, Inc. <wo...@planix.com> Avoncote Farms <wo...@avoncote.ca>
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