[caiman-discuss] swap & dump on ZFS volume

[jan damborsky]

Hi Mike,


Mike Gerdts wrote:
> On Thu, Jun 12, 2008 at 8:55 AM, jan damborsky <Jan.Damborsky at sun.com> wrote:
>> I have gone through the specification and found that
>> following formula should be used for calculating default
>> size of swap & dump during installation:
>>
>> o size of dump: 1/4 of physical memory
>> o size of swap: max of (512MiB, 1% of rpool size)
>>
>> However, looking at the source code, SXCE installer
>> calculates default sizes using slightly different
>> algorithm:
>>
>> size_of_swap = size_of_dump = MAX(512 MiB, MIN(physical_memory/2, 32 GiB))
>>
>> Are there any preferences which one should be used or is
>> there any other possibility we might take into account ?
>
> On large systems with 300+ GB of RAM (no zfs, however) I've never seen
> a case where more than 8 GB was needed.  I typically configure such
> systems to have 16 GB dump devices just to be safe.  1/4 the size of
> RAM would be bigger than the the boot drives in some of these systems.
>  As the default memory footprint of servers gets bigger and the push
> to solid state disks (likely even smaller than 2.5" SAS disks) is
> gaining attention, I would vote for something that puts an upper bound
> on the size.

This is a good point. I agree with you that specifying some reasonable
upper limit should be incorporated in the formula.

Thank you for sharing your observations !
Jan