It's a reasonable limitation stated by NetApp after thoroughly testing the overall throughput capabilities of a fibre channel interface. They found that on busy systems, with a reasonably distributed I/O (WAFL) mix, the FC-AL will become saturated or incurred extended wait states as more disks are added to the FC. They picked an even interval, based on shelf size, closest to the maximums. They also addressed reliability and processor performance concerns. Too many disks on one link will increase the probability of a single point of failure. On NetApp's larger systems separate fast PCI busses support multiple FC interfaces. This architecture and set limitation assures that disks don't have wait on a FC and FC interfaces, running at max speed, don't end up waiting PCI buss throughput. As FC, disk transfer speeds and buss architectures change these recommended limits (54) may change again too.
Hunter .
Hunter M. Wylie 21193 French Prairie Rd St. Paul, Oregon 97137 Bus: 503-633-8900 FAX: 503-633-8901 Cell: 503-880-1947
-----Original Message----- From: owner-toasters@mathworks.com [mailto:owner-toasters@mathworks.com] On Behalf Of Waters, G Scott (DSTI) Sent: Friday, April 25, 2003 12:09 PM To: 'Clawson, Simon'; jeff.mery@ni.com; toasters@mathworks.com Subject: RE: FC9 & DS14 on same FC-AL adapter...
I am curious about the 56 disk rule. To what does it apply. I ask that because I currently have a filer with 63 disk in one loop and no *known* problems.
Please enlighten me.
Thanks.
- Scott W. -----Original Message----- From: Clawson, Simon [mailto:simon_clawson@mentorg.com] Sent: Wednesday, April 16, 2003 11:26 AM To: 'jeff.mery@ni.com'; toasters@mathworks.com Subject: RE: FC9 & DS14 on same FC-AL adapter... Yes. We have FC7, FC9 and DS14 on the same loop.
The rules are - the shelves must be linked in order of oldest to newest - FC7 -> FC9 -> DS14. You cannot have more than 56 disks on one loop.
Simon -----Original Message----- From: jeff.mery@ni.com [mailto:jeff.mery@ni.com] Sent: 16 April 2003 16:16 To: toasters@mathworks.com Subject: FC9 & DS14 on same FC-AL adapter...
Fellow Toasters, Does anyone know if FC9 and DS14 shelves can co-exist on the same FC-AL adapter? If so, are there any special rules that must be followed (i.e. DS14s at beginning/end/certain shelf IDs etc.)?
Thanks in advance, Jeff Mery, MCP National Instruments
------------------------------------------------------------------------ - "Allow me to extol the virtues of the Net Fairy, and of all the fantastic dorks that make the nice packets go from here to there. Amen." TB - Penny Arcade ------------------------------------------------------------------------ -
