3490e carts hold 720 meg non compressed. If hardware compression yeilds 2:1
then getting 1.3-1.4 gig per tapes is doing well. As far as your Sterling
backup software is concerned, does it do it's own compression? What blksize
does it use? We use FDR, and not only does it do compression, it also writes
larger than 32K block sizes (not readable by anything but FDR) such that *most*
of our 3390-3 (2.7 Gig) backups will fit on 1 cart.
ADSM writes 32760 or smaller blocksizes (at least in AIX). Smaller blksizes
mean more IRGs and less data per cart.
I run with compression turned on for most clients, and I'm seeing a range of
820-905 MEG per cart with the average somewhere around 850 each. :)
-Al
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Subject: 3490E Tape Capacity
Author: Steve Fletcher <SFletcher AT GIANTOFMARYLAND DOT COM> at ~Internet
Date: 11/12/97 9:53 AM
I have a question regarding what kind of tape capacity I should be getting with
3490E tapes. We
are in the process of implementing ADSM for a variety of clients (Netware, NT,
and several flavors
of Unix). I am currently backing up about 35 gigs (during the weekly full
backups) off of six
Netware servers. The data on these servers consists of application software
(Lotus, Paradox,
WordPerfect, etc.) and the corresponding data files for these applications. The
MVS server is
installed on an IBM 9672 CMOS processor with EMC drives for disk pools and IBM
3490 C22
tape drives. We are using 3490E tapes and from what I can tell from the
documentation and
various postings on this list, I should be getting over 2 gigabytes of data on
each tape. In reality, I
am getting less than this amount with an average around 1.3 gigs. Compression
is turned off on
the client and it is activated on the device class. When I turn it off on the
devclass, the utilization
drops to about 800 megs per tape. Reclaimation is not the issue (tapes less
than 100 utilized)
since I have tapes in the storage pool which are marked as 100% utilized but
containing only
about 1.3-1.4 gigs of data.
I know the drives are capable of compressing the data more, since our mainframe
backup system
from Sterling Software, is writing around 2.4 gigs per tape. This can be viewed
through CA1 by
looking at the block count and record length.
What do I need to look at and modify to try and get the tape utilization upto
expected amounts??
Thanks!
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