[plug] SAN Advice

[Adrian Woodley]

I have to disagree with you here - FC will _always_ beat NFS for speed. 
And iSCSI isn't even worth considering.

FC headers are 24bytes long. Thats it.

NFS involves many more layers, each with their own frame header, which 
reduces the data:header efficiency:

NFS (???bytes) + TCP (20bytes) + IP (20bytes) + Ethernet (14bytes) + 
checksum (4bytes) = 58bytes

FC HBAs are hardware accelerated, taking much of the load off the CPU. 
NFS relies on the system to negotiate almost every layer in the stack.

To get the same through-put as FC, you'll be spending $$$ on top-shelf 
hardware (accelerated NICs, stupidly fast switches, etc). Much more than 
you'd spend on a comparable FC system.

Thats all assuming you'd max-out any available bandwidth. If you're 
access requirements are more modest, then you can get away with NFS (or 
even iSCSI *shudder*)

I will concede that NFS is easier to implement and potentially more 
flexible. However with the advent of clustered filesystems such as GFS 
and Lustre, multiple hosts accessing the same filesystem at the block 
layer is being much easier.

Adrian

Nathan Alberti wrote:
> 
> 
> Go NAS (NFS), simpler, more flexible and typically cheaper to implement 
> than SAN, you will get as good if not better performance than ISCSI/FC 
> with the right combination of NIC's, Switches and NFS server config.
> 
> Nathan.
>