Uplink ports used for iSCSI?

November 15, 2012 at 19:05:13
Specs: N/A

We have a single HP 2810 switch being used for an iSCSI SAN.
We want to replace it with dual higher end switches.
But we've got another SAN to also setup now - Dell Equallogic PS6010E - that has 10gb iSCSI SFP+ ports.
Can the 4 x SFP+ uplink ports on the Dell PowerConnect PCT5548 or the HP 3800-48G-4SFP+ switch be used for just the 10gb iSCSI, while the other 48 handle the 1gb iSCSI?
We were told the uplink ports don't have buffering, making them bad ports for iSCSI traffic and only useful as uplinks to another switch.
We only need 8 x 10gb ports (4 for 2 servers, and 4 for the Equallogic SAN), so if the above would work, it would probably save us $10,000 from having to buy a separate 24 port dedicated 10gb switch to handle it.

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#1
November 15, 2012 at 21:27:28

I'm not familiar with any of the equipment you mention and have no interest in looking up the spec's of said equipment for you in order to answer your question. If you were asking about equipment I'm familiar with I would be able to answer your questions off the top of my head. But I have no interest in looking up equipment I'll never use. I'm sure you understand.

The information you seek should be in the manual for said equipment. If it's not there, contact the manufacturer and ask them. But I suspect you will be able to find it in the manual.

It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.

***William Henley***


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#2
November 17, 2012 at 05:45:24

Thank you Curt

I probably didn't ask the question in the right way with my specifying specific switch brands/models. I wasn't looking for you to do my due diligence, I can do that.

Based on the equipment you do work with, have you worked with switches that have 10gb uplink ports that work well as dedicated 10gb iSCSI ports instead, rather than uplink ports, and has packet buffer memory been an issue in those that you've worked with?


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#3
November 17, 2012 at 07:10:33

Our 10 GB switches don't have iSCI connections. Our SAN/NAS is rather a large one and it uses FiberChannel connectors between the SAN/NAS heads and the units themselves and have dedicated fiberchannel switches built into the racks.

As far as I know, our switches don't use "packet buffer memory" but each manufacturer has a tendency to reinvent the wheel when it comes to naming things so I could be familiar with this under another name.

Our 10 GB switches are non-blocking so we get the full 10 GB across all connectors.

I would say you need to compare throughput on the two different connectors and go with whatever is going to give you what you the best throughput.

It matters not how straight the gate,
How charged with punishments the scroll,
I am the master of my fate;
I am the captain of my soul.

***William Henley***


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#4
November 17, 2012 at 12:58:37

Thanks Curt, that helps a bit.
Me and my boss just inherited this whole setup - HP2000 SAN, HP4000 SAN, Dell Equallogic SAN, a couple EMC SANs (300 and 320), a single iSCSI switch and a couple fiber channel Brocade switches for the EMCs, and no 10gb switches to even make use of the Equallogic. It's kind of all over the place.
I'd probably say I have about 2 or 3 month's experience with this stuff now. 25 years in tech, but not with SANs, and little with switches.
And the budget axe is falling again (K-12 school district.)
So we're trying to make sense of what we have, and how to go forward with it, so all input and experienced knowledge is appreciated.
And if I sound ignorant, please forgive me on that - trying to keep 6 plates spinning, and we've only got 5 sticks to spin them on.

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#5
November 17, 2012 at 13:10:04

I also don't know the translation yet of 'packet buffer memory' to other vendor's setups.
But I believe it's probably needed in some way even on fiber channel switches.
It's a buffer on the switch, sometimes per port, sometimes per port group, that helps alleviate the dropping/re-sending of packets in case one side is overloaded at the moment and needs a little more time to finish before it gets more packets.
That buffer, or cache, or page file, or swap file, or maybe other terms as well, is a really short term temp storage place in case of packet backup on the reciever end I believe - a way to buffer what's going through - like the 7 second delay on TV when they have to bleep things, I guess. I don't know if that makes sense, but that's my understanding of it at this point.

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