[SunHELP] Swap Memory

[Greg]

On 10/20/2002 12:38 AM, Frank-Christian Kruegel wrote:
>>It sun recommends to have swap less than my memory??
> 
> In case of a kernel panic the system dumps its memory to the swap slice for
> later investigation, and it will be unable to do so with less swap than
> physical memory.

Only kernel memory is dumped by default and that tends to be a small 
fraction of all available physical memory.  Modern versions of SunOS also 
compress the memory pages written to the swap device which further reduces 
the size of the total crash dump.  Even if you use dumpadm to specify that 
all memory pages are to be written to crash dumps, you still won't need 1x 
physical memory for the swap device in order to obtain a successful crash 
dump.  Modern versions of SunOS also allow you to specify a separate crash 
dump device so if you really want zero swap you can still obtain crash 
dumps.  See dumpadm(1m) for all of the details.

A nice feature: savecore -L.  If there's something wrong with a machine 
(eg, hung serial device) but you aren't able to schedule a reboot then you 
can take a crash dump "on the fly" if you use a dedicated dump device.  A 
kernel developer can then analyze the minor problem while your system 
remains operational.

-greg