On Fri, Sep 14, 2007 at 08:31:03AM +0100 or so it is rumoured hereabouts,
Michael Watterson thought:
> It's a crossover cable so switches, network etc don't matter.
>> How fast does it go if the destination is disk? (40MBps ?)
Yep. That was an scp of a 7Gb file.
> What sort of tape unit?
It's an SDLT320 drive in a Dell PV122T autoloader connected via an Adaptec
AHA-3960D card using the aic7xxx driver. Its host is a DELL 2850 running
RHEL 3.
> How fast is the tape unit backup from the local disk?
200Gb took just under 3.5 hours last night. Dump reports:
DUMP: Volume 1 completed at: Fri Sep 14 05:21:16 2007
DUMP: Volume 1 208819200 blocks (203925.00MB)
DUMP: Volume 1 took 3:33:34
DUMP: Volume 1 transfer rate: 16296 kB/s
This is about 10 times the rate reported by dump on the source machine.
> How fast is the source machine copying to itself via loopback "localhost"?
Dunno yet, backup is still running. Will check soon.
> It sounds more like a tape drive issue. How is it connected and what
> else is on its bus?
Nothing else on its bus, just tape autoloader and the tape drive itself.
> David Wilson wrote:
> >What kernels are the machines running? Recent 2.6 kernels had improved
> >sliding window algorithms merged for high speed/high latency links
> >(Google about it, I know little off the top of my head). Try tweaking
> >/proc/sys/net/ipv4 tunables regarding window size (I believe the
> >defaults are fairly useless on high speed links).
tape host is running RHEL3 2.4.21-37.ELsmp
client is running RHEL5 2.6.18-8.el5PAE
> >Also consider playing with ssh, for instance, blowfish encryption can
> >be faster on certain processors compared to the default (I forget what
> >the default is).
> >
> >David.
> >
--
Conor Daly <conor.daly at cod.homelinux.org>
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