> -----Original Message-----
> From: Denys Beauchemin
[...]
>
> However, there are some things that simply cannot be
> compressed.  [...] we amassed multiple gigabytes of data we know to be
> incompressible so we can test the real speed of a device.  [...]  This
> incompressible data is made up of JPEGs, TIFF files saved
> with LZI, and ZIP files. [...]
> I believe video data from a MiniDV camera is highly
> compressed data, which is decoded with some form of MPEG decoder.

That seems to ring a bell -- I've noticed while doing video editing that
some functions work better/faster if the camera is hooked up; seems Adobe
uses the hardware "codec" to deal with video data in real time instead of
using the CPU to decompress it for display...  (and firewire is fast enough
to send a compressed frame to the camera, decompress it on the camera, and
return an uncompressed frame for display at 30fps!)

> If you are experiencing
> higher throughput on this type of LAN without compression
> turned on, rest
> assured that your backup product is attempting the impossible
> and wasting a lot of time doing it.

actually, I noticed that "without compression", the tape "streamed" more
data; with compression caused more "jitter" -- I don't know if that implies
the "client" was taking "too long" to [attempt] to compress the data, thus
leading to a constant "underrun" condition, or if the drive was taking too
long to attempt to re-compress the data, thus having a constant overrun
condition...

> I would suggest 2 things.  First, if there is enough storage
> capacity on your Linux server [...]

Nope.  The linux server was a hacked-together "old" system basically
dedicated to this task -- it has (maybe) a 1gb drive, no "X" window support,
(no monitor for that matter), and a dedicated SCSI controller for the tape
drive

> Second, Hicomp also has a free Linux backup server.
> [...] I would expect no performance difference [...]
> On the other hand, you can control the compression on
> Hiback very easily and there are other advantages.

I'll take a look at it -- Arkeia's method of naming/labelling tapes is a
little awkward [however it appears they will append (daily) backups to the
same tape until the tape is "full" before moving on to the next tape in a
set -- in some instances, this is probably a good thing, but in reality it
just gets in the way...]

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