----- Original Message -----
From: "Fluffles" <[EMAIL PROTECTED]>
To: "Artem Kuchin" <[EMAIL PROTECTED]>
Sent: Wednesday, March 07, 2007 11:35 PM
Subject: Re: Some Unix benchmarks for those who are interesed
Artem Kuchin wrote:
Artem Kuchin wrote:
Hmm. what kind of HDD, RAID or whatever are you using?
My raid pretty much sucks. It is build it on the intel motherboard
LSI Megaraid. But i still get 81Mb/sec when doing
dd if=/dev/ar0 of=/dev/null bs=1M
How much do you get on this?
geom_mirror on 2 desktop SATA drives, but the results of dd are
pretty low:
# dd if=/dev/mirror/data of=/dev/null bs=1m count=1000
1000+0 records in
1000+0 records out
1048576000 bytes transferred in 17.817686 secs (58850290 bytes/sec)
As you can see, results with a single drive are better:
# dd if=/dev/ad4 of=/dev/null bs=1m count=1000
1000+0 records in
1000+0 records out
1048576000 bytes transferred in 16.219518 secs (64649023 bytes/sec)
How is it possible that you get 2x file copy perfomance ? What's the
matter?!
If you use dd on the raw device (meaning no UFS/VFS) there is no
read-ahead. This means that the following DD-command will give lower STR
read than the second:
no read-ahead:
dd if=/dev/mirror/data of=/dev/null bs=1m count=1000
read-ahead and multiple I/O queue depth:
dd if=/mounted/mirror/volume of=/dev/null bs=1m count=1000
You can test read STR best with bonnie (see
/usr/ports/benchmarks/bonnie); or just with DD on a mounted volume. You
should mount with -o noatime to avoid useless writes during reading, or
use soft updates to prevent meta data from taking it's toll on I/O
performance.
Totall disagree. On the following reasons:
1) Read ahead is simply useless when stream-reading (sequential) 1GB of data
2) atime is NOT updated when using dd on any device, atime is related to
file/inode
operations which are not performed by dd
3) soft update are also useless (no bad, no good) for long sequential read
basically, long sequatial reads/write ignore anything but real drive speed
(plate on
the spindle) if they are performed long enough.
I think that 2 times differences is reallty related to seek times. But on the
other
hand i am sure my HDD have very good seek times. I'll have a chance to check
it all on friday.
--
Artem
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