Same for KVM zones, due to the kernel wanting to have every bit of memory allocated also backed by swap. It will also reserve resize the same amount as the ram parameter (with a bit of overhead actually)
On 2016-10-03 09:22, Len Weincier wrote: > Hi > > Thanks for the responses. Of course the LX machines will need the zones/swap > which I did not realize. > > cheers > Len > > On Sun, 2 Oct 2016 at 23:42 Nigel W <[email protected]> wrote: > >> On Sep 29, 2016 2:03 PM, "Len Weincier" <[email protected]> wrote: >>> >>> Hi >> Hi >> >>> >>> We have some new hosts with 1.5T memory and this causes a zones/swap of >>> 1.5T to be created. >>> Is this necessary in the GZ ? Each VM gets its own swap so just not sure >>> what would be running in the GZ that would end u using that swap ? >>> >> >> Yes, it could be a good idea depending on your use case. >> >> If you are using LX or joyent zones, they are assigned out of the GZ's >> resources and the since the illumos kernel does not over commit memory, all >> memory allocated by a process must be backed in the GZ in either RAM or >> swap, so having 0.5x to 1x "max_physical_mem" in "swap". >> >> KVM zones are a bit different because they will have their own swap as part >> of the allocated zvol using whatever mechanism the guest OS uses. However, >> even heavy KVM zone hosts benefit from a lot of swap because they need to >> allocate all of the guests memory up front so having a large swap helps deal >> the memory fragmentation as the host gets to capacity. >> >> Of couse because the swap is just a zvol, you can reduce the swap dataset if >> you like using using the normal zvol commands: >> >> zfs set volsize=<size> zones/swap >> >> I don't recall if shrinking zones/swap needs to be done while the host is in >> noimport mode though. > > SMARTOS-DISCUSS | Archives [1] [2] | Modify [3] Your Subscription > [4] Links: ------ [1] https://www.listbox.com/member/archive/184463/=now [2] https://www.listbox.com/member/archive/rss/184463/26452851-88b650c7 [3] https://www.listbox.com/member/?& [4] http://www.listbox.com ------------------------------------------- smartos-discuss Archives: https://www.listbox.com/member/archive/184463/=now RSS Feed: https://www.listbox.com/member/archive/rss/184463/25769125-55cfbc00 Modify Your Subscription: https://www.listbox.com/member/?member_id=25769125&id_secret=25769125-7688e9fb Powered by Listbox: http://www.listbox.com
