The following was just a short note I wrote in an internal discussion about FCoE vs. iSCSI vs. NFS – and spurred by Tony Bourke’s discussion about methods for implementing FCoE.
This wasn’t intended to be a detailed analysis, just a couple of random musings. Comments as always are welcome.
While NFS and iSCSI are completely different approaches to accessing
storage, they both “suffer” from the same ailment – TCP. Remember folks,
TCP was developed in the 70’s for the express purpose of connecting
disparate networks over long, latent, and likely unreliable links. The
overheads placed onto communication solely to address these criteria
simply aren’t appropriate in the datacenter. We’re talking about a
protocol written to support links slower than your Bluetooth headset. 🙂
iSCSI is a hack, plain and simple. It solves a cost problem, not a
technology one. Even its name is misleading – iSCSI. It isn’t SCSI over
IP – it’s SCSI over TCP over IP. So call it tSCSI or tiSCSI.
I’m not saying they’re not “good enough”, but why do “good enough” now
that “better” is getting much closer in price? On the array side, I
expect more and more vendors to go the NetApp route – all protocols in one
box – just turn on which ones you want to use (via appropriate licensing,
of course). 10G DCB makes this even easier and more attractive – one
port, you pick the protocol you’re comfortable with.
As one of my coworkers points out, FCoE is a bit of a cannon – and for many customers,
their storage challenges are more in mosquito scale.
Fibre Channel was developed with storage in mind as a datacenter protocol,
I haven’t seen one yet I like better for moving SCSI commands around *in
the datacenter*. I’m sure someone will develop a new protocol at some
point that utilizes DCB-specific architectures to replace iSCSI and
FCoE… but why? If you want a high performance, low latency,
made-for-storage protocol, run FC over whatever wire you feel like. If
you want a low-cost solution utilizing commodity
hardware/switching/routing, use iSCSI and/or NFS. I don’t know that
there’s a new problem to solve here.
For customers that already have and know FC, FCoE is a no-brainer.
Nothing new to learn about how to control access, you’re just replacing
the wires. iSCSI and NFS introduce whole new mechanisms and mindsets into
accessing storage if you’re not used to them.
I saw a quote the other day that said that Fibre Channel is like smoking –
if you’re not already doing it, there’s no reason to start now. I get
the sentiment, but I don’t agree. FC as a protocol is the right tool for
a lot of jobs – but it’s not the right tool for every job.