Re: [Xen-users] disk backend performance

[Thomas Halinka <lists@xxxxxxxxx>]

Am Freitag, den 28.11.2008, 16:22 +0100 schrieb Stefan de Konink:
> On Fri, 28 Nov 2008, Thomas Halinka wrote:
> 
> > i do not need any benchmarks. i measured that iscsi could saturate a
> > GB-Link with about 55-60% - AoE was about 80-85% at less CPU-Usage!
> 
> My benchmarks for iSCSI vs NFS performance tests both saturate the links
> 10GE ->  1GE, while the first has a bit better < 10% performance.

A GBit-Link has a maximum throughput of 110 MB/s and you really got
about 100 MB/s? ;)

i think it was about maybe 65 MB/s

> 
> > Why is FC faster than iSCSI? Ah, it s because of the protocol.
> 
> Non-sence.

Nope.

Waht is a SAN? It s a bunch of disk, some intelligence (striping,
mirroring,caching...) and a connection to servers.

It doesn't matter which protocol you 're using: FC, FCoE, AoE or iSCSI
to connect.

All of them implement a SAN for you.

The difference between those techniques is how data is transferred.

and in fc and aoe you only have 2 layers, which to have to be passed.
iscsi has more layers, that are passed and every layer which is passed
produces overhead.

so: less layers = less overhead = more performance.

> 
> > >  and preferably stability comparisons.
> >
> > open-iscsi has no stable releases yet. aoetools do have. There are also
> > many users complaining about iscsi-kernel-issues....
> 
> ...there is more than open-iscsi, in targets and initiators. (+ OS'es)

you're right, 
.....
Linux seems to have better support for AoE than for iSCSI, which is
probably because AoE is simpler and has less peculiar bits. (There is a
certain enterprisey smell about iSCSI.)

http://utcc.utoronto.ca/~cks/space/blog/tech/FCvsiSCSIvsAOE

> 
> 
> Stefan
> 
Thomas


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