HP 3000 Manuals HP 3000 Manuals
Dump Performance and Disk Space Requirements
by Amy Blocher
Commercial Systems Division
This article describes the estimated disk space requirements for remote
dump analysis on MPE XL systems. Ensuring disk space is available for
dump storage continues to be a requirement for remote dump analysis. To
help plan for enough disk space to restore dump files or to dump to disks
via AutoRestart/XL (refer to note), estimated maximum disk space for
various system configurations are provided in the following table. This
article also provides estimated dump performance figures.
Dump disk space is determined by the amount of main memory, the number of
active processes, the amount of dump worthy data per process, and the
dump compression rate. The amount of dump worthy data per process and
the dump compression rate vary depending on system activity. The dump
compression rate can vary between 30% and 70%. However, an average rate
of 40% has been observed and is used to approximate the disk space
requirements in the following table. The dump time performances and
sizes included in the table are estimates.
For dumps which span multiple tapes, a tape rewind and change time of 4
minutes per reel is included in the Dump Time to Tape. For calculating
the number of tapes needed to dump to tape, it is assumed that we are
dumping 150 Mbytes per reel at 6250 bpi on a 7980A tape drive (without
hardware compression). By dividing the average number of tapes created
on a 7980A tape drive by two, one can approximate the number of dump
tapes if a 7980XC tape drive was used instead of a 7980A.
To use this table, locate the approximate total number of processes and
the amount of main memory corresponding to your system. For example, to
dump a system with 75 processes and 96 megabytes of main memory requires
at most an estimated 10 minutes and 150 megabytes of disk space.
You may approximate the number of processes on your system by multiplying
the total number of jobs and sessions by 3. The actual number of
processes per job or session may actually be larger depending on the type
of applications on the system.
Estimated Estimated
Maximum Max Auto- Estimated
DUMP/XL Restart/XL Maximum
Dump Time Dump Time Avg # Disk Space
# Active Main Memory to Tape to Disk Tapes @ Requirement
Processes Size (Mb) (min) (min) 6250 bpi (sectors)
--------- ---------- -------- -------- --------- ------------
24 16 5 5 1 205,000
24 5 5 1 205,000
96 5 5 1 410,000
75 16 5 5 1 410,000
24 5 5 1 410,000
96 10 5 1 615,000
150 16 10 5 1 615,000
24 10 5 1 615,000
96 10 5 1 615,000
300 16 10 5 1 615,000
24 10 5 1 615,000
96 15 10 2 820,000
600 128 20 10 2 1,230,000
256 25 15 3 1,640,000
512 35 15 4 2,255,000
1200 128 35 15 4 2,255,000
256 40 20 4 2,460,000
512 50 25 5 3,075,000
1024 70 30 7 4,510,000
1800 128 50 25 5 3,075,000
256 55 25 6 3,485,000
512 65 30 7 4,100,000
1024 90 40 9 5,325,000
2400 128 65 30 7 4,100,000
256 70 30 7 4,305,000
512 80 35 8 4,920,000
1024 100 45 10 6,145,000
If improved dump performance is desired, AutoRestart/XL (HP36375A) may be
purchased (refer to note). Aside from dump performance, HP recommends
that a non-system doma in volume set be dedicated for remote dump
analysis. Potentially, the non-system domain volume set may not only be
used for dump storage, but also for other HP support files. Depending on
the environment, ad ditional disks may need to be purchased for this dump
volume set.
NOTE AutoRestart/XL (HP3637 5A), a component of the HP high availability
architecture, facilitates an operato rless environment in the event
of a syst em failure. The product automatically invokes du mp to
disk and system startup after a failure. With AutoRestart/XL, dump
performance is improved by approximat ely 35% over dump to tape
because of the faster disk data transfer speed.