[ovirt-users] VSDM Hosts Swapspace

[Doron Fediuck]

----- Original Message -----
> From: "Matt ." <yamakasi.014 at gmail.com>
> To: "users" <users at ovirt.org>
> Sent: Saturday, October 18, 2014 6:33:54 PM
> Subject: [ovirt-users] VSDM Hosts Swapspace
> 
> Hi All,
> 
> As I'm not a big fan of swapping, as most people don't I think, I
> wonder why the following calculation is made:
> 
> The default overcommit ratio is 0.5.
> 
> The recommended size of the swap partition can be determined by:
> 
> Multiplying the amount of system RAM by the expected overcommit ratio,
> and adding
> 2 GB of swap space for systems with 4 GB of RAM or less, or
> 4 GB of swap space for systems with between 4 GB and 16 GB of RAM, or
> 8 GB of swap space for systems with between 16 GB and 64 GB of RAM, or
> 16 GB of swap space for systems with between 64 GB and 256 GB of RAM.
> 
> Example recommended SWAP calculation for a machine with 16 GB of RAM:
> 
> (16 GB x 0.5) + 8 GB = 16 GB
> 
> 
> Would VM's make the Host swap that fast when the mem is overcommitted
> ? I have tested this and don't see much more than 1,5GB of swap usage.
> 
> I hope someone can tell me how they see/use this.
> 
> Matt

Hi Matt,
just a general headsup;
The engine is getting reports on swap usage in the hosts, and by default
will not allow it. This means that no VM will be allowed to start or migrate
to a host actively swapping. It is possible to change it, but highly unwanted
based on past experience.

Doron