In <1994Mar23.195127.22131 AT draper DOT com>, zzgcp AT mgh DOT com (Greg
Piney) writes:
>Subject: AdStar/DSM VM CPU utilization
>
>I have just received a preliminary accounting report for AdStar/DSM.
>Boy is this disturbing. We run on a 9221-130, TCP/IP, 3172 Ethernet
>bridge. All backups to 3480 Carts.
>
>OS/2 Backups are the least expensive
>
There are 2 kinds of ADSM clients - those which don't have reliable
swapping and those that do. The developers coded the incremental
baackup process differently for each kind. For OS/2 AIX, SUN, etc
when a client connects and indicates to the server the an incremental
backup (IB) is do be done, the server makes a list of the current
folders and files that IT knows about and sends it to the client, one
FILESPACE at a time. Then the client compares this list to the
current hard disk and sends the new files, changed files and deletion
signals. Since a filespace can be pretty big, a lot of client storage
is required, thus the need for reliable swapping.
For Macs (my particular problem), DOS, Windows, and netware IBM took
theconservative approach to getting an incremental done. Send from
the server the minimum sensible unit of work, name current server
knowledge by FOLDER, thereby minimizing the requirement for client
RAM. All would be well except that the server doesn't 'put its
finger' on the position within the filespace (which is the basic unit
of file organization in the server). When the client says 'get next
foldere' the server goes back to the top and works its way down.
Imagine the processing on 500 folders! It goes up geometrically.
The current CSD's for mac and windows support the option -
slowincremental on/off
The default is on which eats the cpu. Set it to off to save cpu.
besure to give the client enough ram or swap space to hold all the
data sent from the server for the largest FILESPACE on the client.
DOS will probably not be fixed. The default for netware is OFF. See
if your users have changed it to on to save ram. The documentation
only discusses the effect of this option on the client - no mention of
high cpu in the server.
We are 75% Macs. At one time ADSM took 6 hrs a day. Today with this
fix plus the latest server fix which implements 'expire inventory' it
take 1.5 hrs while doing 1/3 more work.
These fixes will reduce the cpu for a 'null incremental', that is the
amount of cpu you will always spend. Measure it by doing another IB
right after one that sent files.
AIX will appear to be piggier than OS/2 because the filespaces are
typically much bigger as is the case for most unix boxes and probably
netware servers (I don't have any).
[tooting my own horn - I have signed up to give and ADSM user exp
talk at Share 83 in Boston. This will be one of the subjects.]
>Windows Backups use 50-300% more CPU
>
>AIX is a Real Dog
>
>NetWare -- 900 cpu seconds to backup 400 meg/8000 objects
>
>This will cause us to do some serious re-thinking about offering the
>service to our user community. If just every LAN server wanted the
>service, I would need a 5 day weekend to back them all up.
>At the miniscule prices we charge our users, that Netware Backup
>would cost $200. It should cost no more than $40. Believe me, we have
>trouble getting them to spend $40 of funny money on a regular basis.
>
>I would love to see AdStar/DSM be a success. At the prices I would have
>to charge, it would be cheaper for each LAN server to purchase
>a PC tape drive and a couple cases of tapes.
>
>Something has to give.
>
>Speaking only for myself,
>
>Greg Piney
>Sr. Systems Engineer
>My opinions only, not those of
>McGraw-Hill Inc.
>ZZGCP AT mgh DOT com
Bill Colwell
C. S. Draper Lab
Email: BColwell AT draper DOT com
Voice: 617-258-1550
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