From owner-freebsd-virtualization@freebsd.org Thu Aug 27 17:51:38 2015 Return-Path: Delivered-To: freebsd-virtualization@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id C34B09C229E for ; Thu, 27 Aug 2015 17:51:38 +0000 (UTC) (envelope-from vivek@khera.org) Received: from mail-wi0-x22f.google.com (mail-wi0-x22f.google.com [IPv6:2a00:1450:400c:c05::22f]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G2" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 582F29BE for ; Thu, 27 Aug 2015 17:51:38 +0000 (UTC) (envelope-from vivek@khera.org) Received: by wicgk12 with SMTP id gk12so16591145wic.1 for ; Thu, 27 Aug 2015 10:51:36 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=khera.org; s=google11; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=luzyKxd8uLeAKwq868zsbYuAFaS3CB6R5yAtcSvVLcE=; b=UiwJ/fNPYNyLq/OW3HQ4KMuknt363fehQg2GfScucLvjDS3OcmcckZ7Uco5KveoojN sjU1N/1zzjoR+1j398a71/8psdc1sPI6TMYc+HqL7az5jl+jgYgt/p9JYvc26dOa1+B4 9ndPLPx6BotsaDa5g3615sX1MyJM7dhf2CNJM= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:date :message-id:subject:from:to:cc:content-type; bh=luzyKxd8uLeAKwq868zsbYuAFaS3CB6R5yAtcSvVLcE=; b=gAFrXcSuFBjryQAGbPyTtrnv8Js+THWSvGgc8MjZRVLEPRVvSolWz3d+1/T1eC5oxv CDxIIDdnm3jOHb/3DWbxaysS83xUX9k34Mo9Pa01gQenuJ/gsa/ztVxhL33E9bvYDBza 39jOI/c7Dz1TpI4wKQ3GeNVHOJnkd6KKi+WZNZhv76q4lbuDV4gyktTPa6e8MA+LbtEn HEukZnwvNXRhpypqfsaRfXjpHe6KILNO8Eh2MPVdSQQdiLXunVrBr+cyS3aVlxohjMUn pW7IUt69TXCFOMvEG32p/frV5ObGtBZOQb6lCYnhVQOj2v0E+4VZ+YKI3ikv+Qdfgufi roSg== X-Gm-Message-State: ALoCoQknYT+wrHwm4zVpDoGH322yW8icueD2UDe7zuac5YcKz2Rxj4NhK/YwTMfy/mQR4ZB2EDPn MIME-Version: 1.0 X-Received: by 10.180.23.33 with SMTP id j1mr11713213wif.44.1440697896531; Thu, 27 Aug 2015 10:51:36 -0700 (PDT) Received: by 10.28.188.132 with HTTP; Thu, 27 Aug 2015 10:51:36 -0700 (PDT) In-Reply-To: References: <20150827061044.GA10221@blazingdot.com> <20150827062015.GA10272@blazingdot.com> <1a6745e27d184bb99eca7fdbdc90c8b5@SERVER.ad.usd-group.com> Date: Thu, 27 Aug 2015 13:51:36 -0400 Message-ID: Subject: Re: Options for zfs inside a VM backed by zfs on the host From: Vick Khera To: Marie Cc: Matt Churchyard , Marcus Reid , "freebsd-virtualization@freebsd.org" Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable X-Content-Filtered-By: Mailman/MimeDel 2.1.20 X-BeenThere: freebsd-virtualization@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: "Discussion of various virtualization techniques FreeBSD supports." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 27 Aug 2015 17:51:39 -0000 On Thu, Aug 27, 2015 at 6:10 AM, Marie 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.