HP-UX System Administrator's Guide: Overview
Disk Space Needs
Use this section if you have very limited disk resources for the post-crash dump and/or
the post-reboot save of the memory image to the HP-UX file system area. The factors
you have to consider here are:
• Dump Level
• Compressed Save versus Non-compressed Save
• Partial Save (savecrash -p)
Dump Level
You are reading this section because disk space is a limited resource on your server.
Obviously, the fewer pages that you have to dump, the less space is required to hold
them. Therefore, unless your server also has a small amount of physical memory, a full
dump is not recommended. If disk space is very limited, you can always choose no
dump at all.
However, there is a happy medium, and it happens to be the default dump behavior,
which is called a selective dump. HP-UX does a pretty good job of determining which
pages of memory are the most critical for a given type of crash, and saves only those.
By choosing this option, you can save a lot of disk space on your dump devices, and
again later, in your HP-UX file system area. For instructions on how to do this, see
HP-UX System Administrator’s Guide: Routine Management Tasks.
Compressed Save versus Non-compressed Save
Regardless of whether you choose to do a full or selective save, whatever is saved on
the dump devices usually needs to be copied to your HP-UX file system area before
you can use it.
If the disk space shortage on your system is in the HP-UX file system area (not in the
dump devices), you can choose to have savecrash (the boot time utility that does the
copy) compress your data as it makes the copy.
Partial Save (savecrash -p)
If you have plenty of dump device space but are limited on space in your HP-UX file
system, you can use the -p option to the savecrash command. This command copies
only those pages on dump devices that are endangered by paging activity (the pages
residing on devices that are being used for both paging and dumping). Pages that are
on dedicated dump devices are not copied.
102 Major Components of HP-UX