Re: [Xen-users] RAID10 Array

[Adi Kriegisch <kriegisch@xxxxxxxx>]

Hi!

> > Some people mention problems with bonding more than two NICs for iSCSI as
> > the reordering of the commands/packets adds tremendously to latency and 
> > load.
> > If you want high performance and avoid latency issues you might want to
> > choose ATA-over-Ethernet.
> 
> Interesting. I always imagined that iSCSI was going to be the clear
> winner in the case of one NIC as the hardware offloading should more
> than compensate for the overhead of TCP, but I guess you lose all of
> that when you start bonding links together, especially on the receive
> side of things.
The charme of ATA-over-Ethernet is that bonding isn't needed at all for
using multiple links. You even don't need HSRP and stuff like that for
redundancy. The "Ethernet" part in AoE means that ATA commands are embedded
in ethernet frames. Load balancing happens just automagically by using all
available interfaces; no special configuration is needed for this.

> Some adapters have iSCSI specific acceleration, but I don't know if that
> works with bonding at any level.
It will not as bonding normally isn't supported by NICs. To support such a
thing, NICs would need shared memory and a shared dedicated processor that
is able to handle this -- which in practice is the CPU and memory of the
host operating system.

-- Adi

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