Hello,
Not all tapes are created equal in length, so if you see couple of GB less 
or more then advertised capacity that should be OK.Once the networker 
reaches the end of tape it will mark  it full, even when full capacity is 
not reached due to tape length variations.
HTH



Paula Ehn <pehn AT CC.UMANITOBA DOT CA> 
Sent by: EMC NetWorker discussion <NETWORKER AT LISTSERV.TEMPLE DOT EDU>
03/06/2008 12:03 PM
Please respond to
EMC NetWorker discussion <NETWORKER AT LISTSERV.TEMPLE DOT EDU>; Please respond 
to
Paula Ehn <pehn AT CC.UMANITOBA DOT CA>


To
NETWORKER AT LISTSERV.TEMPLE DOT EDU
cc

Subject
Re: [Networker] compression or lack there of






I've added up size reported from the savesets on a tape and it still 
adds up to 792-793GB not something more than that.

Like I said before our old AIT-3 tapes were set the same and showed a 
vast difference in how much Networker put on the tapes, from 
150GB-350GB.  It's for the most part the same data so it should compress 
the same. It's just not writing more than 792-794GB to a LTO-4 tape.

Paula

Howard Martin wrote:
> I think the hbn device will still compress you might get a bit more on 
> using just bn.
> 
> A 800 GB native tape when not using compression won't show a lot 
different 
> to 800 GB on it under Networker as it reporting how many bytes were sent 

> to the drive. Networker doesn't say the the 792GB represents say 3TB of 
> data and therefore the tape contains 3TB.
> 
> Hope that makes sense.
> 
> On Thu, 6 Mar 2008 12:04:39 -0500, Paula Ehn <pehn AT CC.UMANITOBA DOT CA> 
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
>> --
>> -----------------------------------------------------------------
>> | 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  |
>>
>> To sign off this list, send email to listserv AT listserv.temple DOT edu and 
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=========================================================================
> 
> 
> 

-- 
  -----------------------------------------------------------------
| 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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