Hi,

Our setup is such that its rare that all four tape drives are going at
once.  Usually its just 2 drives that are active at any given moment.
Most of our network is Gbit fiber, so in theory we should be able to
deliver enough data to keep two drives fed properly.

The issue that caused me to look at hardware compression is that we
recently consolidated several volumes into one.  The new volume
currently contains about 160 Gbyte and will only get bigger.  The volume
is mounted on our backup server and is physically located on a EMC
Symmetrix via fiber channel, so there is no network between the volume
to be backed up and the Networker server.

Our backup server is a HP K570 with 6 CPUs.  With software compression
it was taking about 6.5 hours to backup the 160 Gbyte.  With hardware
compression enabled last night, it took 3.5 hours.  Thats about a 45%
increase in backup speed.

We do have other clients that are backed up.  Most of them are on Gbit
network, and are still configured to use software compression.  With
software compression enabled, and using the hardware-compression-enabled
devices last night, I saw about a 10% increase in overall backup time
versus what I usually see, which is acceptable.

And yes, I do know that writing software-compressed data to a
hardware-compression drive isn't going to provide any meaningful
improvement in compression versus using only one or the other
compression methods, but


On Wed, 2004-08-04 at 20:59, Yura Pismerov wrote:
>     I have a question for you. Does the hardware compression really help
> in your setup ?
>     Is your network speedy enough to provide sufficient uncompressed
> stream in order to keep the drives at their full speed ?
>     You have mentioned you have 4 AIT-3 drives. To keep them busy (with
> hardware compression on) you should feed each of them with 30-35 MB/s,
> which comes to 120-140 MB/s for all of them.
>     I remember I tested hardware compression at some point and I found
> that it increased our backup timeframe by 50%, just because the data
> stream was not sufficient to feed the drives.  So I  switched back to
> software (client side) compression.

--
Note: To sign off this list, send a "signoff networker" command via email
to listserv AT listmail.temple DOT edu or visit the list's Web site at
http://listmail.temple.edu/archives/networker.html where you can
also view and post messages to the list.
=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=*=