Miles Fidelman wrote:
> Maciej Browarski wrote:
>> Hello,
>> I read, and know, that ZFS + XEN are not works well together. (I've only
>> 512MB for Dom0).
>> How I can disable/off all ZFS stuff to have more usable memory to Dom0.
>>
>>
> Let's ask the reverse question as well: what does it take to get ZFS and
> Xen to work well together?
Ha! :-) When you talk about performance, it all
comes down what problem your trying to solve.
Having a 16-32 core, 64-128G machine what you
want to run as a dedicated VM server vs a
laptop that you want to run X and a guest or
two are very different problems..
Some general tuning hints..
o If you want to run xVM and zfs on your laptop, you
should limit the amount of memory zfs will use for
the arc. The more memory zfs gets, the better it
will perform.. I would say that 64M would probably
be the smallest I would set it to.. But the zfs folks
would probably have better guidance. The higher it
is, the better it will perform.
set zfs:zfs_arc_max = 0x4000000
o If you want to use dom0 as a normal system e.g. login,
run X, apps, and run guests, you should have at least
1G reserved for dom0. This of course depends on how
many apps you want to run and how much memory they use,
etc. Don't forget, those apps are using the same memory
HVM domains use for IO, etc. You should also make sure
you don't balloon dom0 down below 1G by setting the
following xend smf property (takes affect on next reboot).
When you shutdown guests, you can balloon your dom0
back up to max mem.
config/dom0-min-mem integer 1024
o If you are running a dedicated VM server, you should
fix how much memory dom0 has by using dom0_mem on
grub's menu.lst kernel line, and having xend's
config/dom0-min-mem SMF property match it. You should
also shut down services that you not going to use on
dom0, e.g. cde-login, etc. If your using zfs, you
need to size the dom0 mem and zfs:zfs_arc_max
according to your performance needs. I do not have
numbers for those... I would suspect it varies
on your zfs setup (number of disks, pools, raidz,
etc).
o If you are running a large memory system, e.g. 4-128G+,
you should only use NICs and storage HBAs which can
DMA to all 64-bits of IO address space. This makes a
huge difference in metal IO performance and even more
of a difference in xVM dom0 IO performance.
If anyone else has some hints, please share.
> Personally, I'm really interested in putting together a system with
> Opensolaris and XFS as dom0, supporting
> a variety of domUs. That would be a big win.
>
> Now, if one can add clustering to that, it would be a really big win.
Initially, I think clustering will be more interesting
across domUs running on separate dom0s.
MRJ
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