Backup Central

Here are some very unscientific numbers from
time htparm -T -t /dev/device
on a 2.4 Ghz P4 connected to a Western Digital WD2500J on a
fedora core1 system. (Only the -t output and 'sys' time are shown)

Direct IDE (UDMA100):
Timing buffered disk reads: 162 MB in 3.00 seconds = 54.00 MB/sec
sys 0m2.700s

Connected by firewire:
Timing buffered disk reads: 64 MB in 3.05 seconds = 20.98 MB/sec
sys 0m2.140s

Connected by USB 2.0:
Timing buffered disk reads: 4 MB in 5.39 seconds = 759.93 kB/sec
sys 0m1.820s

Maybe it is just my super-cheap combo enclosure, but this looks like
the USB connection is too slow and I didn't even try to mirror with
it. It would might be reasonable to pull a few files off if
needed, though - I'll probably set up my laptop for that possibility.

I am currently running the internal IDE and external fireware
combination as a raid1 mirror and it does not seem to have any
impact on operation speed.

---
Les Mikesell
les < at > futuresource.com




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I wouldn't believe the results you're getting from hdparm, particularly for
buffered disk reads. UDMA100 can't go 54Mb/sec - I believe it maxes out
around 30Mb/sec

Try using something like bonnie++ to get a real indication of how well your
disk / filesystem performs.

Regards,
Josh.

On Tue, 10 Aug 2004 04:06, Les Mikesell wrote:
Here are some very unscientific numbers from
time htparm -T -t /dev/device
on a 2.4 Ghz P4 connected to a Western Digital WD2500J on a
fedora core1 system. (Only the -t output and 'sys' time are shown)

Direct IDE (UDMA100):
Timing buffered disk reads: 162 MB in 3.00 seconds = 54.00 MB/sec
sys 0m2.700s


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On 10 Aug 2004, Les Mikesell wrote:
Here are some very unscientific numbers from
time htparm -T -t /dev/device
on a 2.4 Ghz P4 connected to a Western Digital WD2500J on a
fedora core1 system. (Only the -t output and 'sys' time are shown)

[...]

Connected by USB 2.0:
Timing buffered disk reads: 4 MB in 5.39 seconds = 759.93 kB/sec
sys 0m1.820s

That is USB 1.1 or 1.0 speed, not USB 2.0 speed; the later should be
comparable to firewire in most cases. If your performance were not dead
on the best 1.1 performance it would be less suspicious.

Maybe it is just my super-cheap combo enclosure, but this looks like
the USB connection is too slow and I didn't even try to mirror with
it.

Probably your host hardware is only 1.1, or you only have a 1.1 driver
compiled (or loaded) into the kernel.

Regards,
Daniel
--
There's real teaching: taking the risk and telling people what
you really think, why you think it, and what difference it makes.
-- Prof. Jacob Neusner, commencement address, 1991



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