[DRBD-user] Measure throughput and latency on drbd 8.4

Marco Marino marino.mrc at gmail.com
Tue Jan 24 12:08:14 CET 2017

Note: "permalinks" may not be as permanent as we would like,
direct links of old sources may well be a few messages off.


Hi, I'm trying to test drbd performance using
https://www.drbd.org/en/doc/users-guide-84/ch-benchmark#s-measure-throughput
for throughput and
https://www.drbd.org/en/doc/users-guide-84/s-measure-latency for latency

I have some questions:
I'm using 2 vms for testing purposes. Measure latency and throughput using
vms is a good idea? Should I expect valid results?

Actually when I try to use the script for throughput I have wrong values:
20MB/s when I try to write on /dev/drbd3 (obtained with drbdadm sh-dev
<resource>)


2.0GB/s when I try to write on /dev/disk/by-id/ata-QEMU_HARDDISK_QM00011
(obtained with drbdadm sh-ll-dev <resource>)
Command is:
dd if=/dev/zero of=/dev/disk/by-id/ata-QEMU_HARDDISK_QM00011 bs=512M
count=1 oflag=direct


Is there a way to do a valid test in my environment??

Furthermore, a test of this type should destroy metadata on the resource.
Is this true? How can I check if metadata are ok? it seems that drbdadm
down <resource> and drbdad up <resource> working well.... but I think this
is not correct


Thank you
Marco
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