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Re: [Networker] compression or lack there of
2008-03-09 19:40:37
Hi,
I also am not surprised.
I have LTO-1, LTO-2 and LTO-3 drives. We also use client side
compression
to save LAN traffic, disk space (on advanced file devices) and data
passing
trough the hosts and SAN while cloning.
One thing that these drives do to keep streaming, is to write some
filler
in if the in-coming data is not fast enough. I do not know what the
parameters
of this process, but it causes more tape to be used while writing the
same
amount of data.
Another thing is that the file separators (EOF marks) do not count as
data, but
do count for tape usage.
I do not get 400GB on my LTO-3s but I get 395-397GB. I get 201-207GB
on my LTO-2s.
On 07/03/2008, at 4:04 AM, Paula Ehn wrote:
Hi gang!
Is anyone out there using LTO-4 tape drives without hardware
compression?
I'm trying to figure out if I have a problem with the tape drives,
Networker
or the drivers/patch in Solaris.
We use Networker's compression on the client side so that we are
transferring a smaller amount of
data over our LAN to the backup server. To avoid compressing the
data twice,
we have compression turned
off on our LTO-4 tape drives. For expample, we use /dev/rmt2hbn
instead
Problem is I'm seeing
consistantly that only 792-794GB are being put onto each tape.
We use to use this same configuration when we used AIT-1 then later
AIT-3
tape drives and saw a wild spread in the amount of data being put
onto a
given tape. For AIT-3 it was anywhere from 120-320GB depending on how
compressable the data was.
For LTO-4 I'm expecting a similar spread but not less than the native
capacity on the tape which is 800GB. I expect it to
read better then 1TB on a tape at least.
Any ideas?
Networker 7.2.2 Jumbo (server and client)
Solaris 9
STK SL500 library with 4 HP FC LTO-4 tape drives.
Devices in Networker set to LTO-3 (LTO-4 option not available in
7.2.2) and
default capacity set to 1600GB.
We are planning to upgrade first the server this year to Solaris 10
and then
Networker to 7.4.x but not until summer.
Thanks!
Paula
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