[mdlug] External Hard Drive as Backup

[Dan Pritts]

> Does firewire offer higher speeds than usb

Firewire does most of the work for you, but USB requires your CPU
to do most of the heavy lifting.  This along with some architectural
details which i don't know much about makes Firewire faster.  

whether you care or not is another question - for occasional use
running backups, USB is probably plenty fast.

i didn't check the methodology of the two tests below but they are
interesting.  The thing that's really notable is the speed of esata
vs. usb or firewire on the second link.   If you really want fast,
go esata.

Firewire 800 would be better but esata is cheaper and potentially
faster.

  http://www.usb-ware.com/firewire-vs-usb.htm
    Read Test:
    * 5000 files (300 MB total) FireWire was 33% faster than USB 2.0
    * 160 files (650MB total) FireWire was 70% faster than USB 2.0

    Write Test:
    * 5000 files (300 MB total) FireWire was 16% faster than USB 2.0
    * 160 files (650MB total) FireWire was 48% faster than USB 2.0


  http://www.everythingusb.com/seagate_freeagent_pro_750gb_hard_drive_12613.html
    Speed: 30-33MB/s (USB 2.0), 31-37MB/s (FireWire 400), 49-57MB/s (eSATA)


> or can I open my options a little by dispensing with
> firewire? Should I consider paying a little more and getting a NAS with
> ethernet?

A NAS system will almost certainly be a lot slower than any of the
other options.  

You might say, hey, 1G ethernet is 125MB/sec, that should be plenty
fast enough that it shouldn't be the bottleneck.  You'd be right -
the bottleneck is the file sharing protocols.  Your PC likely doesn't
have a good enough ethernet card to get full line rate, either.
"server" ethernet cards like the intel e1000 really are better.

that said, nas is a lot more flexible.

i bet it would be hard to make it be bootable even if it has
some sort of USB mode.  


>     Once I get one, how should I format it so I would be able to sync
> two notebooks with /root, /boot, /usr, /swap, /var, /tmp, /opt
> and /home partitions. Just two ext3 partitions, one for each notebook?

I'd do one big filesystem.  
Consider this:

  http://www.mikerubel.org/computers/rsync_snapshots/

> It would also be nice to be able to boot directly from the
> 'backup' drive via usb or other, must I do something special for that to
> happen?

if you just do a mirror of your boot drive, you probably will be OK
but make sure your kernel and/or initrd has all the USB-storage support
you will need to boot from usb.  You would have to install a bootloader
on the external drive too.  (grub or lilo)

random hint - if you do buy a firewire drive, get one that also has
USB so you can use it on some firewire-less computer in the future
if you want it.  says the guy who decided to save a few bucks by
dropping the USB support and wishes he didn't.

danno
--
dan pritts
danno at umich.edu
734-929-9770