Archive for January 6th, 2009

Network Hard Drives: Why Not

The question came up as to whether an external hard drive with a network interface was a Good Thing for backups and suchlike.

For humongous drives, a 100 Mbit/s network tap is painfully slow. In round numbers, on a good day you’ll get 80 Mbit/s throughput; call it 10 MBytes/s.

Transferring 1 TB at 10 MB/s requires a bit over a day: 28-ish hours. Streaming media will work fine, but filling up the drive in the first place will be tedious.

I was reminded of this the hard way when I had to do a full-drive backup to the file server in the basement. Seemed to take forever, but when I ran the numbers it was ticking along just about as fast as it could possibly go…

A USB local drive is better: 40 MB/s, more or less, if the software stack can keep up with it. I eventually pulled the drive, popped it on a USB-IDE adapter, jacked it into the server, and got it done that way.

Now, if you have gigabit Ethernet everywhere, things might be faster, but the limiting factor then becomes the drive’s sustained rate, which is probably a tad over 100 MB/s if you’re transferring large files.

Fancy eSATA drives have a higher burst rate, but the bits just don’t come off the platters all that much faster.

I’d be astounded if a consumer-grade network drive came anywhere close to those numbers. I have an IOmega 500 GB drive that’s an absolute piece of crap…

Feed the obvious keywords into Wikipedia and get all the numbers.

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