Re: [ovirt-devel] VDSM changes Linux memory dirty ratios - why?

On 30/11/16 09:13, Yaniv Kaul wrote: > Thanks, but it really makes no sense to me. The direct IO by the VMs is > going to a different storage than what the host is writing to, in most > cases. > The host would write to the local disk, the VMs - to a shared storage, > across NFS or block layer or so. Moreover, their IO is not buffered. > There is very little IO coming from the host itself, generally (I hope > so!). > > Partially unrelated - the trend today is actually to put NOOP on the VMs - > the deadline is quite meaningless, as the host scheduler will reschedule > anyway as it see fits. > Most likely it is also a deadline scheduler (but could be NOOP as well if > it's an all flash array, for example). Therefore there is no reason for > anything but simple NOOP on the VMs themselves. > > In short, I think it's an outdated decision that perhaps should be > revisited. Not urgent, though. > Y. I know it's not the most cared about usecase but I'd like to add that this might affect local storage domains, which I happen to use a lot, and maybe others too.

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