Hello guys, I've been playing around with disk QOS on ACS 4.2.1 and KVM and noticed several issues.
The first issue that I've discovered is that if you attach a QOS enabled disk to a _running_ vm the QOS settings on the disk are not passed on to the hypervisor. Example of the xml file using virsh dumpxml: <disk type='network' device='disk'> <driver name='qemu' type='raw' cache='none'/> <auth username='admin'> <secret type='ceph' uuid='cf771bc7-8998-354d-8e10-5564585a3c20'/> </auth> <source protocol='rbd' name='Primary-ubuntu-1/ee1551bc-50ce-42b1-85a3-9441ac43e1b0'> <host name='ceph-mon' port='6789'/> </source> <target dev='vde' bus='virtio'/> <alias name='virtio-disk4'/> <address type='pci' domain='0x0000' bus='0x00' slot='0x08' function='0x0'/> </disk> where as it should have an <iotune> block like this: <iotune> <read_bytes_sec>100000000</read_bytes_sec> <write_bytes_sec>100000000</write_bytes_sec> <read_iops_sec>100</read_iops_sec> <write_iops_sec>100</write_iops_sec> </iotune> However, if you stop and start the guest vm, the <iotune> blocked is passed on like it should. Has anyone noticed this behaviour? Second issue that i've discovered (and it is likely an issue with KVM itself) is that the QOS limitation for the read throughput seems to be 4 times lower in benchmarks than what is shown in iotune block. For example, i've limited the read and write throughput to 100,000,000 bytes. The benchmarks are showing me correct throughput for the write benchmarks, but the read benchmarks are giving me about 25-26MB/s instead of around 100MB/s. Has anyone seen this behaviour? Cheers Andrei -- Andrei Mikhailovsky Director Arhont Information Security Web: http://www.arhont.com http://www.wi-foo.com Tel: +44 (0)870 4431337 Fax: +44 (0)208 429 3111 PGP: Key ID - 0x2B3438DE PGP: Server - keyserver.pgp.com DISCLAIMER The information contained in this email is intended only for the use of the person(s) to whom it is addressed and may be confidential or contain legally privileged information. If you are not the intended recipient you are hereby notified that any perusal, use, distribution, copying or disclosure is strictly prohibited. If you have received this email in error please immediately advise us by return email at and...@arhont.com and delete and purge the email and any attachments without making a copy.
