Hello Mahesh,
We are in the process moving other way, OS/390 to AIX. The reasons we are
making the move are for performance and to avoid a mainframe upgrade due to
high third party software costs.
Some things to consider based on my experience running TSM on OS/390 / MVS
since 1996.
1. Since you are using a G3 mainframe, your only option for attaching your
S/390 to the LAN/WAN network is via some ESCON attached box. This includes
using an OSA-2 card which has ESCON on-board. Simply put, when sending
your IP traffic over an ESCON channel, the best throughput you can expect
is an aggregate rate of 7MB/Second per ESCON channel. We've been able to
achieve 12MB/Sec to the AIX TSM server during a backup of large files over
the ATM pipe.
2. We used to backup about 350GB per day to our MVS TSM server. This
amounted to about 30%(TSM and TCPIP combined) of our 9672-R55 CPU resources
during the 6pm to 6am time frame. Managements view was that S/390 CPU
cycles we too expensive and 30% was too much for a backup server function.
3. How do most S/390 shops manage their workload? Give priority to online
users and lower the priority of any "less critical" workload that consumes
large amounts of CPU. Our capacity and tuning person put the priority of
out S/390 TSM at the same level as a batch job. Over time this was not
high enough for me to meet some of my backup windows.
Where are we today? A little more than half of my TSM workload has been
moved to AIX. Everything is faster, ADMIN Web Client use,
backups/restores, migrations from disk to tape, etc. We are replacing
mainframe software from vendors trying to charge us huge upgrade fee's for
capacity upgrades as well. Now that I'm off on my own RS/6000, I don't
have to fight for my priority in the workload mix, I get better performance
and am better positioned to take advantage of the industry movement towards
sending some of my backups over the SAN versus the LAN/WAN. The cost of the
entire AIX based TSM solution was less than the software costs associated
with adding capacity to our S/390.
I'm not sure what work is being done by Tivoli to reduce the amount of CPU
a S/390 TSM server consumes but I hope they can do something to reduce it.
On the network side of things, the new OSA Express, available on G5 or
higher mainframes which takes ESCON out of the picture and off the OSA,
might provide a much faster pipe into the S/390. Maybe someone else on the
LISTSERV running an OSA Express with a S/390 TSM server could share their
experiences on throughput.
You mentioned you use a VTS with your S/390. We have a VTS as well. As
you probably know, your "biggest bang for the buck" with a VTS is for
smaller tape datasets, files that are recalled frequently within a short
period of time, and for applications that don't fill tapes. Applications
that can fill a tape to capacity, like TSM, might better be sent to a
direct host attached 3590 tape drive than to your VTS. If you think about
it, TSM appends to tapes until full. If a volume is no longer in the Tape
Volume Cache, a number of back-end recalls from physical tape to the TVC
could result during backups. Or as data on your VTS TSM tapes expires,
reclaimation will cause a lot of VTS backend tape mounts and recalls to
cache as well. This would be in addition to the reclaimation peformed for
logical volumes by the VTS itself. My recommendation would be to not put
your TSM S/390 backups in the VTS and send them to S/390 direct ESCON
attached 3590's in your 3494.
I guess the bottom line is, if you have the spare cycles on your S/390 and
you have enough ESCON attached boxes between your S/390 and the network to
meet your service levels then go for it. As a mainframe person for 20
years it pains me to say it but running TSM on a RS/6000 has proved to be a
better option for me so far.
FYI - our TSM configurations look like this:
S/390
9672-R55
OS/390 V2.6
TSM for OS/390 V3.7
IBM 2216 with two ESCON and two 155mbit ATM interfaces
Two Cisco CIP in two Cisco 7513 routers with ATM and Fast Ethernet
interfaces.
300 TSM clients that include Windows NT/2000, AIX, HPUX, Solaris,
Sybase/SQL-backtrack, Lotus Domino
TSM database 35GB 62% utilized. Cache hits 98%.
TSM client and server options tuned properly.
Eight ESCON attached 3590E1A Magstar tape drives in a 3494 ATL
EMC 5930 disk for TSM database, recovery logs and disk storage pools
AIX
RS/6000 H80 two-way with 2GB memory
EMC 5430 disk for TSM database and storage pools
TSM DB 33GB cache hits 98%
Six 3590E1A Fibre Channel tape drives in same 3494 ATL as S/390 drives
Two Compaq Fibre Channel switches with two FC host adapters in the
RS/6000
TSM for AIX V4.1.2
Same client types as backed up to the S/390 TSM server
Two Fast Ethernet adapters and one ATM.
Our network consists of Fast Ethernet between servers with an ATM backbone.
All ATM adapters use Classical IP and not LAN emulation.
Hope this helps,
Jeff Connor
Niagara Mohawk Power Corp
Mahesh Tailor <MTailor AT CARILION DOT COM>@VM.MARIST.EDU> on 06/11/2001
11:01:14
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Subject: TSM on OS/390
Hello, all.
I am currently running TSM v3.7.4.0 on AIX and would like to migrate it
to OS/390.
The server currently has 200 nodes (IBM AIX, HP-UX, Novell Netware 4 & 5,
Microsoft Windows NT) registered and our schedules start at 20:00 and
finish by 06:00. The total storage is 2.8TB.
The mainframe is an ES-9000 (9672-R34) and using VTS system for storage.
What I'd like to know is what overhead to expect on the OS/390 or how to
figure out if I'm going to have to upgrade the system? Also, should we
create a new image for TSM? What are licensing issues for this
migration?
Any information would be appreciated.
TIA
Mahesh Tailor
WAN Administrator
Carilion Health System
Voice: 540-224-3929
Fax: 540-224-3954
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