[Bug 212681] I/O is slow for FreeBSD DOMu on XenServer

[bugzilla-noreply at freebsd.org]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=212681

karl at pielorz.com changed:

           What    |Removed                     |Added
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                 CC|                            |karl at pielorz.com

--- Comment #1 from karl at pielorz.com ---
Hi,

We run XenServer 6.5 and 7 here - with a range of FreeBSD versions (mostly 10.x
now). We've not noticed any really low I/O performance.

How are you running dc3dd? - So I can try and install / replicate this here.

We have seen that I/O behaves differently under XenServer than it does on bare
metal (which is obvious - i.e. local SATA SSD vs. Multipath iSCSI [or similar])
you will see differences (even just with 'mapped through XenServer' "Local
Storage").

It could be dc3dd / the stuff you're running is a particularly 'bad case' for
the I/O. e.g. In an equally 'synthetic' test - a regular "dd if=/dev/zero
of=test.dat bs=64k count=10240" on our our test pool here (which has two paths
iSCSI over Gigabit) we get around 220Mbyte/sec to a FreeBSD DomU.

That may well be a best case - and you may well have hit some worst cases.

-Karl

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