LTO compressions doesn't have a problem with double compression - you
should leave it in place to compress all the stuff that isnt compressed
- like the index backups, when it encounters pre-compressed data it
transparently passes it through..

The native capacity is stated as 800GB but 792 is close enough isnt it?
Might vary a few gigs depending on the tape manufacturer... If you send
compressed data to it then that's about what will fit on the tape -
seems good to me. 


-----Original Message-----
From: EMC NetWorker discussion [mailto:NETWORKER AT LISTSERV.TEMPLE DOT EDU] On
Behalf Of Paula Ehn
Sent: Friday, 7 March 2008 4:05 AM
To: NETWORKER AT LISTSERV.TEMPLE DOT EDU
Subject: [Networker] compression or lack there of

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
-- 
 -----------------------------------------------------------------
| Paula Ehn  VE4MHZ/VE4HZ                    Room E3-628 EITC     |
| Unix System Administrator             pehn AT cc.umanitoba DOT ca |
| Academic Computing and Networking          (204)474-7849        |
| University of Manitoba                    Fax: (204) 474-8534  | 

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