On Aug 05, Brian Tao wrote:
On Wed, 4 Aug 1999, Matt Harrington wrote:
These NFS vendors speak about benchmarks in ops/sec. It's more intuitive for me to think of benchmarks in terms of MB/sec throughputs for a large file write or read.
This is because local storage will always be faster than NAS ifthe only thing you look at is raw sequential throughput.
...
[But for file system operations, sometimes] NFS will seem faster despite a raw bandwidth disadvantage.
Always is a long time!
Historically, the wires to disk drives (e.g. SCSI) have always been faster than the wires to networks (e.g. Ethernet), but networking wires have been gaining ground. Gigabit Ethernet has the same raw bandwidth as Fibrechannel. And if you look at the next generation, networking folks are talking about 10 Gb Ethernet, while the storage folks are talking about 2 Gb and 4 Gb Fibrechannel. I admit that TCP/IP imposes an overhead on Gb Ethernet, even though Gb Ether and Fibrechannel have the same raw bandwidth, but when you look at the trend lines, you have to admit that network performance has made amazing gains.
Plus, the raw bandwidth of disk drives is not improving as quickly as either type of wire. So increasingly, the bottleneck is moving out of the wires, and into the disk drive itself. This is especially true if any seeking is involved, but I believe it's even true of raw disk head bandwidth.
I don't want to get in a fight about when exactly the cross-over will occur, or even if it definitely will occur, but given the different trend lines, I think it's worth considering the possibility that NAS really could match local storage, even just in terms of raw disk performance, as opposed to file system ops, and maybe even surpass it.
Amazing and counter-intuitive things can happen when different technologies improve at different rates. When you finally reach a cross over point, as seems to be happening now with networking and storage wires, it can really turn the world upsidedown.
Dave