topic Re: Data Transfer rates in Operating System - HP-UX

Data Transfer rates

David Muise — Fri, 19 Dec 2003 11:11:34 GMT

I have an N4000 with an A6795A Fibre card connected to a 2Gbs McData switch port, connected to an EMC Clariion CX600. The whole pipeline is 2Gbs. Clariion has Fibre drives and ATA drives. Drive specifications indicate that average transfer rates should be in the 60 MB/sec range. H.P. Performance Assessment tools and sar output indicate I'm only getting @14-15 MB/sec. Any ideas on why this is and where to look for increasing these performance figures. Using LVM, VxFS in filesystem mode.

Re: Data Transfer rates

Steven E. Protter — Fri, 19 Dec 2003 11:23:26 GMT

You will never get the full 60 MB/sec

There is OS overhead, router/switch overhead and other tasks that impede actual performance.

The speeds you are getting are about twice what I"m getting on the 1 GB network cards(Cat 5) I just installed on my L class servers.

So, you are actually doing pretty well. We have a much faster core switch than you do, top of the line Cisco equipment.

I ran an scp test for this reply and am getting 9.3 MB/s on our core switch.

There may be some mounting options that help in /etc/fstab but you'll have to get them from other replies.

SEP

Re: Data Transfer rates

Paula J Frazer-Campbell — Fri, 19 Dec 2003 12:05:25 GMT

David

The manufature will always rate the equipment he/she are producing tested in the optimum of conditions, a card rated at 2Gbs will on a good day with a following wind using real world data be very lucky to hit 60% of its rated value.

Each device in the chain running at 60% will pass data at 60% of what it receives so:-

2Gbs Lan card circa = 1.2 gig
router receives 1.2 gbs sends at 0.72 gig
switch receives this 0.72 gig - sends at 0.432 gig and so on.

So fairly quickly the data rate is decremented.

HTH

Paula

Re: Data Transfer rates

Leif Halvarsson_2 — Fri, 19 Dec 2003 12:30:26 GMT

Hi,
The 60MB/s is (as I think) raw performance, perhaps what you get if you read/write direct to the raw device file. With a filesystem involved there is much more overhead, how much depends on the average filesize. If you have (for example) Data Protector you can try a disk image backup to /dev/null. I think you will get a very good transfer rate.

There is another factor, perhaps more interesting then the raw performance with filesystem and database usage, IOPS (I/O per second).