[ovirt-users] info on performance of cloning a snapshot

[Gianluca Cecchi]

Hello,
I'm on 4.1.1 environment.
Storage domain is iSCSI (with multipath) and able to write at about 200
MBytes/s when making a test inside a VM (100MB x 2)

While cloning a snapshot it seems the performace is quite lower...
It begins at about 12MB/s (6 x 2) then increases at about 30MB/s (15 x 2)
with maximum of 50MB/s (25 x 2), all balanced across the two iSCSI network
adapters

The related process on hypervisor
vdsm      2772  3701  4 15:47 ?        00:00:08 /usr/bin/qemu-img convert
-p -t none -T none -f qcow2
/rhev/data-center/ef17cad6-7724-4cd8-96e3-9af6e529db51/94795322-92a7-4904-80c1-83d6b629d38a/images/073519dc-440d-418d-9e0c-a7ac4812ea82/845a9008-8ece-4cf2-9828-f286640b5f0e
-O qcow2 -o compat=1.1
/rhev/data-center/mnt/blockSD/94795322-92a7-4904-80c1-83d6b629d38a/images/54c40b95-c0e5-42db-a6ba-c00f8d337fdc/5987e84f-28be-46c4-bc3a-688d5f7fd025

Not a big problem, only to know: is there any limiting/tunable factor in
any vdsm/engine parameter?
Or is it related to the command "qemu-img convert" itself or anything else?
Thanks,
Gianluca
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