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Real aggregate using built-in Mac Pro ethernet?

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Shane Winter
Real aggregate using built-in Mac Pro ethernet?
on Dec 15, 2010 at 10:04:53 pm

One other thing I'm hoping to clear up;

I have 3 Mac pros Connected to xserve-based RAID via 2 ethernet (cat5) links, aggregated with a managed switch. I have conflicting info about whether this setup is using BOTH links at the same time. It hasn't been a real issue as our storage hasn't been fast enough to push it, but with significantly faster arrays on the way, I'm wondering:

A. Are the built-in ethernet ports capable of a real 2Gbps aggregated link for a single program (FCP), or is this effectively just dual channel gigabit, helping with multiple transfers?

B. Will a dual port card like Small Tree's offer a real benefit if the internal ports cannot?

C. Will a software solution like metaLAN help with either hardware approach? Their site mentions support for increased bandwidth via 802.11ad and sounds promising

If anyone's got any test numbers/experience here, i'd love to hear


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Bob Zelin
Re: Real aggregate using built-in Mac Pro ethernet?
on Dec 15, 2010 at 11:09:41 pm

A. Are the built-in ethernet ports capable of a real 2Gbps aggregated link for a single program (FCP), or is this effectively just dual channel gigabit, helping with multiple transfers?

REPLY - no, who told you that? Why do you assume that. You can't link aggregate the client end, just the server end to the managed switch. You are not going to get over 90MB/sec per client, if you put 2 or 4 or 6 ports in the client - you are stuck with the bandwidth of the ethernet protocol, and only jumbo frames will help you.


B. Will a dual port card like Small Tree's offer a real benefit if the internal ports cannot?

REPLY - not on the client end .


C. Will a software solution like metaLAN help with either hardware approach? Their site mentions support for increased bandwidth via 802.11ad and sounds promising

REPLY - no, MetaLAN, and every other product follows the same rules. There are no magic tricks. You want faster than 90MB/sec (peaking over 100Mb/sec) with standard Gig E - move to another protocol, like FCoE, fibre, 10Gig ethernet, or Infiniband. And iSCSI is not faster either.

Bob Zelin



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Shane Winter
Re: Real aggregate using built-in Mac Pro ethernet?
on Dec 16, 2010 at 1:05:05 am

Brilliant...that's the definitive I needed.

To Confirm: Bandwidth is capped per Client-server connection. Server sees >90Mbps only by connection to several machines

So then...the only real benefit I have for my aggregated workstation links is fail-over


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Bob Zelin
Re: Real aggregate using built-in Mac Pro ethernet?
on Dec 17, 2010 at 3:47:04 am

confirmed.

Bob Zelin



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Steve Modica
Re: Real aggregate using built-in Mac Pro ethernet?
on Dec 30, 2010 at 3:36:06 pm

Link aggregation is socket balancing. It's 802.3ad (there are both static and dynamic variants and apple is dynamic only. Cheap switches are often static only).

Clients only use a single socket to connect to the server. The spec requires that each "conversation" (aka socket) must stay on a single port for its lifetime unless there's a failover event. So when you connect to the server, the socket is going to use one port.
The socket coming back from the server may use the other port. So in some instances when you have bidirectional traffic (like during a render with source and destination on the server) you *may* see traffic going on both ports. however I can't guarantee this since Apple has a frustratingly random 802.3ad assignment algorithm. if they offered more flexibility there, we could lock it down and use this effect.

Under "normal" circumstances, you might see traffic on one port going out and the acks (lots of tiny packets) coming back on the second port.

I haven't spent any time looking at the 10.6 802.3ad driver. Perhaps I can hack that to offer a way to lock in unidirectional traffic on each port with our edge-core switches. I'll check.

Jumbo frames are obviously a good thing to use.
Also, with our new 10Gb cards we have RSC supported. So we can aggregate incoming frames to the server. That's a nice feature that helps performance (especially with the imacs that don't do jumbo frames)

Steve


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