Re: [Xen-users] iscsi vs nfs for xen VMs

[Pasi Kärkkäinen <pasik@xxxxxx>]

On Wed, Jan 26, 2011 at 11:10:12PM +0100, Christian Zoffoli wrote:
> Il 26/01/2011 22:24, James Harper ha scritto:
> >>
> >> iSCSI tipically has a quite big overhead due to the protocol, FC, SAS,
> >> native infiniband, AoE have very low overhead.
> >>
> > 
> > For iSCSI vs AoE, that isn't as true as you might think. TCP offload can
> > take care of a lot of the overhead. Any server class network adapter
> > these days should allow you to send 60kb packets to the network adapter
> > and it will take care of the segmentation, while AoE would be limited to
> > MTU sized packets. With AoE you need to checksum every packet yourself
> > while with iSCSI it is taken care of by the network adapter.
> 
> the overhead is 10% on a gigabit link and when you speak about resources
> overhead you have mention also the CPU overhead on the storage side.
> 
> If you check the datasheets of brands like emc you can see that the same
> storage platform is sold in iSCSI and FC version ...on the first one you
> can use less than half the servers you can use with the last one.
> 

This is mostly because of:
        - EMC's crappy iSCSI implementation.
        - EMC wants to sell you legacy FC stuff they've invested a lot in.


See dedicated iSCSI enterprise storage like Equallogic.. the way it's meant to 
be.

Microsoft and Intel had some press releases around one year ago
demonstrating over one *million* IOPS using a single 10gbit Intel NIC,
on a *single* x86 box, using *software* iSCSI.

> Every new entry level storage is based on std hardware without any hw
> acceleration ...for example EMC AX storages are simply xeon servers.
> 

Many of the highend enterprise storage boxes are just normal (x86) hardware.
Check for example NetApp.

The magic is all in *software*.

-- Pasi


_______________________________________________
Xen-users mailing list
Xen-users@xxxxxxxxxxxxxxxxxxx
http://lists.xensource.com/xen-users