[Nagiosplug-devel] check_swap on solaris with metadisk
Thomas Sluyter
nagios at kilala.nl
Tue Jun 13 11:47:51 CEST 2006
Heya...
It seems I can answer my own question :)
> On 6/13/06, Thomas Sluyter <tsluyter at kilala.nl> wrote:
>> db5# swap -l
>> swapfile dev swaplo blocks free
>> /dev/md/dsk/d20 85,20 16 2097392 0
>>
>> db5# swap -s
>> total: 3431360k bytes allocated + 34488k reserved = 3465848k used,
>> 820608k available
> From the man-page of "swap":
> > The blocks column from swap -l reports:
> > The swaplen value for the area in 512-byte blocks.
>
> Also from that man-page:
> > The allocated column from swap -s reports:
> > The total amount of swap space in bytes currently allocated
> > for use as backing store.
>
> So there's a discrepancy right there.
I found the following which provides an answer for the discrepancy
between "swap -l" and "swap -s"...
(from http://www.softpanorama.org/Solaris/Processes_and_memory/
swap_space_management.shtml)
=========
The virtual memory system maps physical copies of files on disk to
virtual addresses in memory. Physical memory pages which contain the
data for these mappings can be backed by regular files in the file
system, or by swap space. If the memory is backed by swap space it is
referred to as anonymous memory because there is no identity assigned
to the disk space backing the memory.
=========
Note - The swap -l command displays swap space in 512-byte blocks and
the swap -s command displays swap space in 1024-byte blocks. If you
add up the blocks from swap -l and convert them to Kbytes, it will be
less than used + available (in the swap -s output) because swap -l
does not include physical memory in its calculation of swap space.
=========
Tricky :) It's something you just -have- to know :)
> df -k is showing
>
> Filesystem kbytes used avail capacity Mounted on
> swap 810152 24 810128 1% /var/run
>
> Which seems to suggest swap is only 800MB with 1% used?
Which in turn is quite odd since "swap -s" reports something
completely different. Any chance of you throwing the full "df -k"
output over here?
> The source for check_swap has the following
> ...
> Which to me suggests that its using swap -s for its calculations?
Yep... Seems that you're right...
>> There's more buginess in check_swap anyway... See below:
> Hmm, maybe worth not using check_swap then!
Yeah,maybe... It would be trivial to write your own shell script
version of check_swap for Solaris :) That way you're 100% sure that
you can trust the incoming data...
Cheers!
Thomas
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