FileSlinger™ Backup Reminder 8-27-04: Why Network Backup is Faster

Dear FileSlinger™ clients, colleagues, and friends:

One of the more tech-savvy readers of this newsletter asked me a question after last week’s post about network backups (slightly edited):

“How can network backups to another computer be faster than Firewire or USB2 backups to an external hard drive if network speeds are 100 MB/second, Firewire is 400 MB/second and USB2 is 480 MB/second? The numbers don’t add up.”

So I asked the Ur-Guru. After all, the network backup he’d performed had looked pretty fast to me—faster than my own backups via Firewire to my pocket-sized XHD—but I didn’t know exactly how that could be.

This was the answer (slightly edited):

“What Steve says is correct. However, Firewire and USB disks are usually slow and the slowness of the disks is the bottleneck. Ergo, you have a 400 MB/second pipe but the disk will only write (save) the data at 200-300 MB/s. Over a network the higher speed IDEs (connectors normally used for drives inside your computer) in computers will often run faster than the xHD ones.”

And, to provide us with a bit of perspective and a telling point:

“In my case when I talk to you about backup over the network I’m running it to machines one a 1000 MB/s link where the disks on the other end will easily handle a 400 MB/s full sustained transfer… that is by far faster than any xHD or USB/FW device…. but that is not the common setup.”

(It’s not common because a 1 GB/s network is amazingly expensive to install and difficult to find cables for, and most people who aren’t Ur-Gurus don’t need it anyway.)

“A network backup (100 MB and up) is faster than a CD-R or DVD-R in most cases.”

(Certainly it’s faster than my DVD-writer, which is an external Firewire device and can only handle DVD-RWs at 1x, which is slow enough to notice.)

“A gigabit (that’s 1000 MB) network will by definition be almost as fast as local IDE disks but not as fast as local SCSI arrays (just to complicate the discussion). :-)”

(For the record, SCSI is another means of connecting drives either inside or outside your computer—very fast and generally very expensive, though it’s one of our oldest technologies.)

And for those Windows XP users out there: it’s a good idea to make a full system backup before installing Service Pack 2, just in case it causes more problems than it solves. (Mac users, you can gloat. For now.)

More backup news next week,

Sallie