[pve-devel] pve-manager and disk IO monitoring

[Dmitry Petuhov]

29.09.2016 09:05, Michael Rasmussen wrote:
> On Thu, 29 Sep 2016 07:38:09 +0200 (CEST)
> Alexandre DERUMIER <aderumier at odiso.com> wrote:
>
>> iostats are coming from qemu.
>>
>> what is the output of monitor "info blockstats" for the vm where you don't have stats ?
>>
>>
> Two examples below:
> # info blockstats
> drive-ide2: rd_bytes=0 wr_bytes=0 rd_operations=0 wr_operations=0 flush_operations=0 wr_total_time_ns=0 rd_total_time_ns=0 flush_total_time_ns=0 rd_merged=0 wr_merged=0 idle_time_ns=0
> drive-scsi0: rd_bytes=0 wr_bytes=0 rd_operations=0 wr_operations=0 flush_operations=0 wr_total_time_ns=0 rd_total_time_ns=0 flush_total_time_ns=0 rd_merged=0 wr_merged=0 idle_time_ns=0
> drive-scsi1: rd_bytes=0 wr_bytes=0 rd_operations=0 wr_operations=0 flush_operations=0 wr_total_time_ns=0 rd_total_time_ns=0 flush_total_time_ns=0 rd_merged=0 wr_merged=0 idle_time_ns=0
> # info blockstats
> drive-ide2: rd_bytes=0 wr_bytes=0 rd_operations=0 wr_operations=0 flush_operations=0 wr_total_time_ns=0 rd_total_time_ns=0 flush_total_time_ns=0 rd_merged=0 wr_merged=0 idle_time_ns=0
> drive-scsi0: rd_bytes=0 wr_bytes=0 rd_operations=0 wr_operations=0 flush_operations=0 wr_total_time_ns=0 rd_total_time_ns=0 flush_total_time_ns=0 rd_merged=0 wr_merged=0 idle_time_ns=0
It's side effect of scsi pass-through, which is being used by default 
for [libi]scsi volumes with scsi VM disk interface. QEMU is just not 
aware of VM block IO in that case. Also, cache settings for volumes are 
ineffective, because qemu is just proxying raw scsi commands to backing 
storage, so caching is impossible.

Do you use PVE backups (vzdump)? Is it works for machines without stats? 
I think it's also shall not work with pass-through.