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Re: [Networker] compression or lack there of
2008-03-07 11:40:14
I have a hard time believing this as I did (at least for the AIT-3
tapes) go back and map the reported saveset sizes to the file systems
sizes and they were not much different. We do about 90% fulls and 10%
incremental backups per tape volume. So I had to conclude that the size
Networker was reporting both for a given saveset and the total on a
given tape was indeed correct or at least close enough to not matter.
I've not yet done the same exercise for the LTO-4 tapes but I suspect
the answer will be the same, Networker is reporting the sizes correctly.
So There is not greater than 793GB on a tape on average.
That being said, perhaps there is little to no client compression going
on but it sure looked like it by the AIT-3 tape numbers we were seeing.
I'll have to dig further here.
Much to my disappointment, it was decided to not use hardware
compression. I'm working on changing that slowly.
Obviously, the tape drives do work and are acting normal as the majority
here see it, so I guess I'll just go buy some more tapes because even
using the LTO-4 at native capacity, it's a far better than the amount we
were getting on the AIT-3's. And boy are those LTO-4 tape drives FAST!
Thanks to all who responded!
Paula
Date: Thu, 6 Mar 2008 12:27:56 -0500 From: Howard_Martin t
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
--
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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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