[Discuss] Home backup disks: USB vs NAS

[jarod at wilsonet.com (Jarod Wilson)]

On Jun 1, 2011, at 11:09 PM, Doug wrote:

> I was looking into setting up a time machine backup disk for the macs
> in the house. There appear to be hundreds of USB2.0 external devices
> which transfer at a rate of ...
> 
> USB 1.0 2mbps

USB 1.0 was 1.5Mbps.

> USB 2.0 Full Speed 12mbps

The 12Mbps standard is USB 1.1.

> USB 2.0 High Speed 480mbps
> USB 3.0 5 gbps
> 
> I am seeing USB 2.0 all over the place, but few references to Full
> versus High Speed. I don't know how common one is versus the other.

If they say USB 2.0, they mean High Speed.

> If one wants the ethernet port, the device becomes a Network Attached
> Storage (NAS). I have 100base-T Ethernet in the house, along with
> 802.11n. Those should provide 100mbps connections to a NAS.
> 
> Western Digital My Book Live sells a 1TB for $130 or 2TB for $150. I
> would think that when you wanted to get something off these disks, NAS
> might make a significant difference if it is 12 versus 100, unless one
> has the High Speed USB which would win in that case (unless the disk
> is limiting somewhere in this range).
> 
> One thing that bothers me about either setup is having these things on
> all the time. Does anyone sell a device that wakes up when needed?

Most NAS devices run a very low-power energy-efficient ARM chip, and
chunks of the device do power down when not needed. The disks likely
spin down as well.

> If you had the choice between a USB backup or NAS at home, which would
> you prefer? Should I even worry about the speed differences for this one
> kind of task?

Personally, I despise USB. I use esata or firewire wherever I can for
external storage devices, both of which are faster than USB 2. I haven't
got a USB3 drive to play with yet, but its just a sata drive behind a
USB3 bridge anyway, so esata is actually likely still faster (no protocol
translation overhead), at least for single disks.

Anyway, both direct-attached and network-attached storage have their pros
and cons, obviously. With network-attached, you aren't reliant on one
host to always be available, and you may even be able to run a number of
services on the NAS (dns, dhcp, file server, etc). But if your network
goes away, you can't get at your data. And if the NAS uses some custom
internal format, it may be hard to get at your data in the event the NAS
hardware croaks. Bus-powered usb/firewire drives can be handy if you want
to make your external storage mobile though.

-- 
Jarod Wilson
jarod at wilsonet.com