[OmniOS-discuss] Upgrade from 151022 to CE bootadm error

[Chris Siebenmann]

> Yes I saw that too, but I'm not sure why 12GB is being taken up by
> rpool/dump.  And there's really not that much used by BEs.  Is there a
> reason that dumps has to be so large or should I allocate more space
> to rpool?  Thanks!

 If I remember correctly, by default rpool/dump is sized during install
based on the machine's physical memory. On machines with any decent
amount of memory this can wind up using up an annoying amount of space,
especially if you're installing on to not-that-huge system SSDs.  My
further understanding is that during crash dumps the kernel will use
whatever free space is available in the rpool (in addition to whatever
is reserved for rpool/dump), so that if you have the free space at the
time you can capture even relatively large crash dumps. All that the
rpool/dump reservation does is either guarantee or increase the chances
that you can capture such large dumps.

 Our habitual practice is to resize rpool/dump down significantly on
our OmniOS machines. I believe we reserve 4 GB by default, and even
that might be considered generous. If you're short of space I wouldn't
hesitate to either delete it entirely or shrink it drastically.

(There are environments where reliably obtaining crash dumps if your
kernel does go down is sufficiently important that it's worth paying for
the extra disk space needed. My personal suspicion is that most people
are not deploying OmniOS in such an environment.)

	- cks