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Re: [Xen-users] AoE (Was: iscsi vs nfs for xen VMs)

Adi Kriegisch wrote:

What AoE actually does is sending a frame per block. Block size is 4K -- so
no need for fragmentation. The overhead is pretty low, because we're
talking about Ethernet frames.
Most iSCSI issues I have seen are with reordering of packages due to
transmission across several interfaces. So what most people recommend is to
keep the number of interfaces to two. To keep performance up this means you
have to use 10G, FC or similar which is quite expensive -- especially if
you'd like to have a HA SAN network (HSRP and stuff like that is required).

AoE does not suffer from those issues: Using 6 GBit interfaces is no
problem at all, load balancing will happen automatically, as the load is
distributed equally across all available interfaces. HA is very simple:
just use two switches and connect one half of the interfaces to one switch
and the other half to the other switch. (It is recommended to use switches
that can do jumbo frames and flow control)

Getting somewhat off-topic, but I'm interested to know how AoE handles network errors ? I assume there is some handshake to make sure packets were delivered, rather than just "fire and forget" !

Simon Hobson

Visit http://www.magpiesnestpublishing.co.uk/ for books by acclaimed
author Gladys Hobson. Novels - poetry - short stories - ideal as
Christmas stocking fillers. Some available as e-books.

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