Re: [Xen-users] tap:aio not working...

[Marcel Ritter <Marcel.Ritter@xxxxxxxxxxxxxxxxxxxx>]

Marcel Ritter schrieb:
> Hi again,
...
> If also found this behaviour when using sparse qcow files:
>
> qcow-create -r 20480 /proj.stand/image.qcow
> xm block-attach 0 tap:qcow:/proj.stand/image.qcow xvda w 0
> ... <insert test above here> ...
>
> works fine, but without "-r (reserve)" flag, it fails miserably:
>
> qcow-create 20480 /proj.stand/image.qcow
> xm block-attach 0 tap:qcow:/proj.stand/image.qcow xvda w 0
> ... <insert test above here> ...
> .... < this takes hours ... or more? Never finished for me)
Update on that (qcow, without reserve):
I was too impatient on that, after waiting quite some time I got this:

while true; do time dd if=/dev/zero of=dummy bs=1M count=10240; done
10240+0 records in
10240+0 records out
10737418240 bytes (11 GB) copied, 3851,42 seconds, 2,8 MB/s

real    64m11.684s         <- took over 1 hour!!!
user    0m0.032s
sys     0m12.569s
10240+0 records in
10240+0 records out
10737418240 bytes (11 GB) copied, 3928,04 seconds, 2,7 MB/s

real    69m0.305s
user    0m0.040s
sys     0m14.485s
10240+0 records in
10240+0 records out
10737418240 bytes (11 GB) copied, 336,601 seconds, 31,9 MB/s

real    5m44.421s
user    0m0.012s
sys     0m14.021s
10240+0 records in
10240+0 records out
10737418240 bytes (11 GB) copied, 111,804 seconds, 96,0 MB/s

real    1m54.282s          <- now, less than 2 minutes
user    0m0.032s
sys     0m13.189s
10240+0 records in
10240+0 records out

Looks like expanding the qcow file the first time takes *very* long, after
that it speeds up considerably (2,8 MB/s -> 96 MB/s), so my next try will be
to run that test again on tap:aio: with sparse file ....

Currently running the same test for tap:aio: again ... running for more 
than 3 hours now ...
> So this is (in short) what works (and what not):
>
> type:      sparse:      works:
> file:/             no               yes
> file:/             yes             yes
> tap:aio:/      no               yes
> tap:aio:/      yes             no
> tap:qcow:/   no              yes
So this should read:
- tap:qcow:/   yes            no
+tap:qcow:/   yes            yes
> So for me it looks like blktap (or some other component) gets into 
> trouble when
> sparse files are used...
>
> Any idea what's the cause of that?
>
> BTW: The system I'm currently testing on is SLES 10 SP2.
Bye,
  Marcel

--
----
Dipl.-Inf. Marcel Ritter
Linux/Novell
Regionales Rechenzentrum Erlangen
Tel: 09131 / 85-27808
E-Mail: Marcel.Ritter@xxxxxxxxxxxxxxxxxxxx
----
Unix _IS_ user friendly... It's just selective about who its friends are.



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