Date: Thu, 27 Aug 2015 13:51:36 -0400 From: Vick Khera <vivek@khera.org> To: Marie <marieheleneka@gmail.com> Cc: Matt Churchyard <matt.churchyard@userve.net>, Marcus Reid <marcus@blazingdot.com>, "freebsd-virtualization@freebsd.org" <freebsd-virtualization@freebsd.org> Subject: Re: Options for zfs inside a VM backed by zfs on the host Message-ID: <CALd%2BdcfCuywjUSDU3JL=oHx2spNJPMtOM5RSs67f1eqLH-wtNA@mail.gmail.com> In-Reply-To: <CALXRTbeXMGCGVfQn3OuOzC3VM3si7RFyEZba=ww36FoKb_224g@mail.gmail.com> References: <CALd%2BdcfJ%2BT-f5gk_pim39BSF7nhBqHC3ab7dXgW8fH43VvvhvA@mail.gmail.com> <20150827061044.GA10221@blazingdot.com> <20150827062015.GA10272@blazingdot.com> <1a6745e27d184bb99eca7fdbdc90c8b5@SERVER.ad.usd-group.com> <CALXRTbeXMGCGVfQn3OuOzC3VM3si7RFyEZba=ww36FoKb_224g@mail.gmail.com>
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On Thu, Aug 27, 2015 at 6:10 AM, Marie <marieheleneka@gmail.com> wrote: > I've tried this in the past, and found the worst performance penalty was > with ARC disabled in guest. I tried with ARC enabled on host and guest, > only on host, only on guest. There was a significant performance penalty > with either ARC disabled. > > I'd still recommend to experiment with it on your own to see if the hit i= s > acceptable or not. > Thanks for all the replies. I'm going with a small-ish ARC on the VMs (about =C2=BC the allocated RAM as max, and very small amount for min) and letting the host have its substantial ARC. Since I'm running with compression=3Dlz4 on the guest, I ended up setting compression=3Dnone on the host for the backing volumes. After some testing = I found I was getting no compression on the backing volumes, so why waste the CPU overhead trying.
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