At Wed, 21 Jan 2026 15:45:40 -0800, "Greg A. Woods" <[email protected]> wrote: Subject: Re: Xen storage for NetBSD guests: performance vs. consistent backups (sanity check) > > In any case I've been using LVM LVs in my dom0s to host raw partitions > for domUs since day one of using Xen, so since NetBSD-5 I think. I find > them to be the most performant and, perhaps more importantly, the most > flexible solution overall. I can easily extend an LVM if more space is > necessary somewhere and then just resize the FFS for the domU, and > they're very easy to configure and manipulate at any time.
This isn't a real benchmark, but here's the results of a simple test:
Simple file I/O performance test from dom0
# dd if=/dev/zero of=testfile bs=1m count=4096
4096+0 records in
4096+0 records out
4294967296 bytes transferred in 18.033 secs (238172644 bytes/sec)
# dd if=testfile of=/dev/zero bs=1m
4096+0 records in
4096+0 records out
4294967296 bytes transferred in 13.247 secs (324221883 bytes/sec)
and from a domU with LVM LV back-end storage:
# dd if=/dev/zero of=testfile bs=1m count=4096
4096+0 records in
4096+0 records out
4294967296 bytes transferred in 14.750 secs (291184223 bytes/sec)
# dd if=testfile of=/dev/zero bs=1m
4096+0 records in
4096+0 records out
4294967296 bytes transferred in 13.381 secs (320975061 bytes/sec)
bonnie-2.06nb3 runs (with "-s 4000"):
-------Sequential Output-------- ---Sequential Input-- --Random--
-Per Char- --Block--- -Rewrite-- -Per Char- --Block---
--Seeks---
Machine MB K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU K/sec %CPU /sec
%CPU
dom0-raw 4000 156980 91.9 268640 87.8 90492 62.1 159257 73.1 265574 51.6 844.5
11.4
dom0-lvm 4000 148048 84.8 269226 89.9 87670 60.3 155711 72.1 258751 51.6 781.0
10.1
domU 4000 196809 95.6 352908 89.3 95027 48.6 183517 82.3 315754 64.2 695.3
10.0
I don't really understand the bonnie numbers vs. the dd numbers.
Both dom0 and domU systems are the same NetBSD/amd64 9.99.81 version.
Both have 4096M of RAM allocated, but the domU can balloon to 12000M.
The dom0 is more or less idle beyond running NTP and whatever demand the
domUs put on it for storage I/O. That domU is running SMTP, IMAP, HTTP,
and nsd, etc.
So I don't think I'm seeing very much of a performance hit from LVM.
--
Greg A. Woods <[email protected]>
Kelowna, BC +1 250 762-7675 RoboHack <[email protected]>
Planix, Inc. <[email protected]> Avoncote Farms <[email protected]>
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