Expected speed of firewire-attached drive?

[Andrew Reilly]

Hi there,

I don't do a whole lot of benchmarking: mostly my computer's
speed is "perfectly adequate", and working reliably is key.

At the moment, though, I'm curious.  I'm sitting here while I
attempt to restore a file from a level-0 dump, and it's taking a
while.  The backup medium is one of those firewire-attached
Maxtor 300G drives, but to make it interesting I compress the
backup image with bzip2 (which keeps the file size down to about
16G).  Dmesg.boot says that the drive is capable of 50MB/s, the
firewire driver says nothing obvious about speed, except "invalid
speed 7 (fixed to 3)." (details below).  The motherboard is a
relatively shiny Athlon X2-4400 NVidia-4 based system, so there
ought to be oodles of compute grunt for this exercise, surely?

Anyway, systat -vmstat says that da0 is doing about 40 128KB
transfers per second, or about 5MB/s (actually a bit under), or
12% busy.  One of the CPUs is pegged.  Hmm, it's pegged running
bzcat.  That would be the bottleneck, then.

OK, so I've answered my own question.  Please consider this post
informative or noise at your discretion: I'm going to post it
anyway on the grounds that it might provoke some interesting
discussion, and perhaps a suggestion for a less cpu-hungry
compression algorithm (I guess I could try gzip for the next
backup...)

Cheers,

from dmesg.boot:
fwohci0: <Texas Instruments TSB82AA2> mem
0xf0004000-0xf00047ff,0xf0000000-0xf00 03fff irq 18 at device
10.0 on pci1 fwohci0: OHCI version 1.10 (ROM=1)
fwohci0: No. of Isochronous channels is 4.
fwohci0: EUI64 00:14:85:56:00:e6:80:b0
fwohci0: invalid speed 7 (fixed to 3).
fwohci0: Phy 1394a available S800, 3 ports.
fwohci0: Link S800, max_rec 4096 bytes.
firewire0: <IEEE1394(FireWire) bus> on fwohci0
fwe0: <Ethernet over FireWire> on firewire0
if_fwe0: Fake Ethernet address: 02:14:85:e6:80:b0
fwe0: Ethernet address: 02:14:85:e6:80:b0
fwe0: if_start running deferred for Giant
sbp0: <SBP-2/SCSI over FireWire> on firewire0
fwohci0: Initiate bus reset
fwohci0: node_id=0xc800ffc1, gen=1, CYCLEMASTER mode
firewire0: 2 nodes, maxhop <= 1, cable IRM = 1 (me)
firewire0: bus manager 1 (me)
fwohci0: phy int
...
da0 at sbp0 bus 0 target 0 lun 0
da0: <Maxtor OneTouch II 0310> Fixed Direct Access SCSI-4 device 
da0: 50.000MB/s transfers
da0: 286188MB (586114704 512 byte sectors: 255H 63S/T 36483C)


-- 
Andrew