This "extra" 1GB is for the qemu process itself and the KVM zone overhead.
-- Brian Bennett Systems Engineer, Cloud Operations Joyent, Inc. | www.joyent.com <http://www.joyent.com/> > On Jul 7, 2015, at 5:26 AM, Schmurfy <[email protected]> wrote: > > Thanks, this explains everything xD > > is there a way to tweak this 1GB number ? I don't get what this reserve is > actually used for since from inside the VM I only see what I allocated, is it > for the qemu process itself ? > > For ZFS how much memory should I give it and what it depends on ? I tried to > find more information on this but I have yet to find a useable formula to > give me a precise idea. > > On 7 July 2015 at 12:38, David Finster <[email protected] > <mailto:[email protected]>> wrote: > For KVM based virtual machines, SmartOS will reserve <ram amount> + 1GB as > soon as the VM is started. The additional 1GB is to manage any potential > temporary overruns inside QEMU/KVM. > > So based on that, you actually created 4 x 3.5GB VMs which would require > 14GB. Keep in mind that ZFS relies on having a decent amount of RAM available > for it to function correctly - you don’t want to get into a situation where a > system has no free RAM (RAM used for ARC cache is free-able). > > You can normally see if your hitting RAM availability problems by starting > the VM and going into /zones/<uuid>/root/tmp/vm.startvm.log. There you will > likely see the progress of locking memory. > > To make the best use of your resources, you should look towards either native > ‘joyent’ brand or ‘LX’ brand zones instead of KVM. Joyent zones are the > SmartMachines you get on Joyent Public Cloud and are a pretty friendly UNIX > environment to work with. LX zones on the other hand emulate a Linux kernel, > are newish and are quite a significant development focus at the moment. > > - Dave > >> On 7 Jul 2015, at 7:55 PM, Schmurfy <[email protected] >> <mailto:[email protected]>> wrote: >> >> Hi, >> >> I was wondering if there is a way to know how much memory I can use for my >> VMs, until now I am almost blind and sometimes it work sometimes it doesn't. >> >> Yesterday I tried to create 4 VMs with each 2.5 GB on a 16GB host and the >> last one failed to provision, I had to reduce its memory to 2GB to make it >> work, without that the VM was shown as runnning but was really not: "vmadm >> info" hanged, no network up, "vmadm console "did nothing. >> >> In this case sometimes I see the provisioning of the VM failed (as shown in >> vmadm list) and other times it appears to work but the VM is in a hald dead >> state like above. >> >> We are a small company and we would really like to use as much as possible >> our current hardware resources, that's why I am looking for a way to >> estimate what ZFS and the host need/use. > > > smartos-discuss | Archives > <https://www.listbox.com/member/archive/184463/=now> > <https://www.listbox.com/member/archive/rss/184463/26986985-d0246faa> | > Modify <https://www.listbox.com/member/?&;> Your Subscription > <http://www.listbox.com/>
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