vn(4) performance on 4.11 versus md(4) on 5.4

[scuba at centroin.com.br]

Hi Glenn,

	Have already fixed that problem?
	Your tests were on the same hardware?
	I´ve tested two of my boxes one with, FBSD 4.9 and another with
the latest cvs 5.4.
	They´re not the same hardware but the performance with md drive
was MUCH faster with 5.4.

	TEsted with 'dd':
	4.9:
dd if=/dev/zero of=TESTE count=1000 bs=64k
1000+0 records in
1000+0 records out
65536000 bytes transferred in 1.005721 secs (65163195 bytes/sec)

	5.4:
dd if=/dev/zero of=TESTE count=1000 bs=64k
1000+0 records in
1000+0 records out
65536000 bytes transferred in 0.241217 secs (271688824 bytes/sec)

- Marcelo Souza

On Sat, 4 Jun 2005, Glenn Dawson wrote:

|
|
|
|I have a number of systems running 4.11 that have file backed virtual
|disks, each of which contains a jail.  I need to start using 5.4 for new
|servers.  The catch is, file backed virtual disks using md(4) seem to be
|much slower than similar virtual disks on 4.11 using vn(4).  vn(4) on 4.11
|is about 2.24 times faster than the equivalent setup using md(4) on 5.4.
|
|I've posted the results of some tests that I ran at
|http://www.antimatter.net/md-versus-vn.txt
|
|Is this decrease in performance known?  Is there something I can do in
|order to come close to the performance that 4.11 has?  I've tried changing
|some of the parameters of the filesystem on the virtual disk, but the
|performance didn't change.
|
|I can supply more info than what the link above has, if needed.
|If I should post this to another list please let me know. (I started here
|in order to avoid cross posting.
|
|-Glenn
|
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- Marcelo