[PVE-User] Slow speeds when KVM guest is on NFS

Mikhail m at plus-plus.su
Tue Nov 15 23:59:15 CET 2016


Here's a clean "dd" test of two identical KVM guests that shows how
results differ (NFS vs LVM):

1) First guest inside qcow2 image, located on NFS share (via 10gbit
ethernet), cache settings "Default (No cache)":

$ dd if=/dev/zero of=test bs=64k count=150k conv=fdatasync
153600+0 records in
153600+0 records out
10066329600 bytes (10 GB) copied, 196.993 s, 51.1 MB/s



2) Second guest runs inside LVM-over-iSCSI logical volume, from the same
storage server, via same as first guest 10gbit ethernet, cache settings
"Default (No cache)":

$ dd if=/dev/zero of=test bs=64k count=150k conv=fdatasync
153600+0 records in
153600+0 records out
10066329600 bytes (10 GB) copied, 58.474 s, 172 MB/s

Mikhail.


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