Bruce is right... the quote as outlined in the e-mail below is incorrect. The exact quote from the Advanced Administration and Troubleshooting "202" Student Guide Dated April 2000 (Page 8 of the performance tuning section) is:
"There is an approximate 10% decrease in write performance when the filer attempts to write to a RAID group spanning two adapters. This is due to inherent limitations in the PCI bus."
Page 41 of the Performance Tuning Section does not specifically say WRITE performance but page 47 does. I'm sure this issue will be addressed in the next version of the course.
Please note... the statement above may no longer apply to the F840 filer (or later filers) or later releases of Data ONTAP. That statement addresses a specific limitation of the PCI bus on Pre-F800 series filers.
As always .... YMMV.
-----Original Message----- From: Bruce Sterling Woodcock [mailto:sirbruce@ix.netcom.com] Sent: Tuesday, September 12, 2000 4:14 PM To: Todd C. Merrill; Chris Lamb Cc: toasters@mathworks.com Subject: Re: 2 volumes or 1
----- Original Message ----- From: "Todd C. Merrill" tmerrill@mathworks.com To: "Chris Lamb" skeezics@measurecast.com Cc: toasters@mathworks.com Sent: Tuesday, September 12, 2000 10:09 AM Subject: Re: 2 volumes or 1
On Mon, 11 Sep 2000, Bruce Sterling Woodcock wrote:
From: "Chris Lamb" skeezics@measurecast.com
But to turn this thread on a slight tangent, I was curious about the performance advantages of spreading drives within a RAID group across multiple controllers.
[...]
interested too. :-) Given that More Disks Is Bettah, the question
becomes
whether or not it's worth the trouble (on a filer) to try to optimize
the
physical placement of those drives.
Worth the trouble? No.
Worth the trouble? Yes IMHO. The NetApp 202 class notes state:
"A RAID group that spans two different controllers shows a 10% performance degradation."
We've been over this before. This note, as written, is grossly false. The penalty is only on writes, and only noticeable if you're already saturating your NVRAM such that you are writing all the time. There is no constant 10% performance penalty.
Bruce