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

[Christian Zoffoli <czoffoli@xxxxxxxxxxx>]

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.

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

Christian

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