topic Re: CRC errors on 2910al with ISCSI in Switches, Hubs, and Modems

CRC errors on 2910al with ISCSI

Tijl van der Steeg — Tue, 29 Sep 2009 10:31:56 GMT

Situation 2 2910al's connected to a "that other vendor" equallogic. Jumbo frames and flow control are enabled. ISCSI and LAN are separated.

Whenever some load is generated, I get an excessive amount of crc errors on the port connected to the equallogic. Performance drops to a few kb/s.

Dell blames the limited buffer(6mb) on the 2910al, and say only a 3500/5400 is supported.
I'd say the 2910al is fast enough for this. anyone that had a similar issue?

Re: CRC errors on 2910al with ISCSI

Bruce Campbell_3 — Sun, 04 Oct 2009 11:24:23 GMT

We haven't tried ISCSI on the 2910al, but
I have some suggestions:

- try turning off jumbo frames on the
switches and equallogics. I've heard
jumbo frames place a bigger load on
packet buffers, and the main performance
improvements people see come from flow
control, not jumbo frames.

- try changing your qos config to
"2-queues" which may increase the
per port buffer size available.

Notes: It is the per port buffer size
that would be useful to know for the
2910al. That 6MB must be a total. The
5400zl has 200-600KB per port, depending
on qos queue configuration. (page 51 at:

http://www.procurve.com/docs/products/techoverview/Technicaloverview4AA0-5388ENWRev3.pdf

). I haven't seen similar specs for the
2910al.

Note that HP doesn't seem to claim that
even the 5400zl will do media speed
with jumbo frames. See:

http://www.hp.com/rnd/pdfs/TollyProCurve5406zlAugust2006.pdf

The published results are for up to 1500
byte packets, and regarding jumbo,
they only say:

"The Procurve 540zl handled the jumbo
frames load delivered by engineers..."

and they don't say what that was.

Re: CRC errors on 2910al with ISCSI

Tijl van der Steeg — Mon, 05 Oct 2009 06:31:21 GMT

Cheers, we disabled jumbo last week. Yeah it's a 5% gain max, and it does give problems in this config.

I came across the qos command before, haven't tried it though, although it is supported on 2910AL.
Unfortunately I can no longer make changes to the switches as the migration is tomorrow night.

Run into a lot of trouble with equallogic, we switched controllers on the SAN machine, and went to a single switch config, and no problems anymore. Their support is lacking they say the 2910AL is not supported while their "ISCSI Optimized" is.

Look at the specs, it's clear that this switch is not half as fast as the 2910

Dell Powerconnect Procurve 2910 AL
Switch Fabric 48 GBPS 128GBPS
Forwarding rate 35.6Mpps 95.6Mpps
CPU SDram 64mb 512mb
Packet buffer size 6MB 6MB
Mac address table size 8000 16.000

Re: CRC errors on 2910al with ISCSI

jacobsstcg — Thu, 19 Nov 2009 01:26:48 GMT

How is the performance on your Equallogic iSCSI? We have a LeftHand SAN connected to two 2610-48 switches and are seeing lots of resends and packet fragmentation which is resulting is very poor throughput. We're going to upgrade to the 2910 so we can turn on both flow control and jumbo. Have you had good luck with the 2910al units or do you wish you would have gone with something bigger, like the 3500?

-Jake-

Re: CRC errors on 2910al with ISCSI

Tijl van der Steeg — Mon, 23 Nov 2009 15:48:11 GMT

Well it turned out to be a faulty controller. We did switch to a 3500yl we had still in stock, and achieved better performance.

Although it says in the manual both flow control Ã¡nd jumbo frames at the same time are supported, we did suffer some retransmits with that setting enabled.

Also, the port buffer of the 2900 is only 6MB, which is OK, but the 3500 has 36mb at least I think. IMO it would be worth the money to opt for the 3500