From owner-freebsd-virtualization@freebsd.org Wed Mar 20 23:30:49 2019 Return-Path: Delivered-To: freebsd-virtualization@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id E464F153E881 for ; Wed, 20 Mar 2019 23:30:48 +0000 (UTC) (envelope-from hausen@punkt.de) Received: from kagate.punkt.de (kagate.punkt.de [217.29.33.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 81C00867B6 for ; Wed, 20 Mar 2019 23:30:47 +0000 (UTC) (envelope-from hausen@punkt.de) Received: from hugo10.ka.punkt.de (hugo10.ka.punkt.de [217.29.44.10]) by gate2.intern.punkt.de with ESMTP id x2KNUkxh042658; Thu, 21 Mar 2019 00:30:46 +0100 (CET) Received: from [217.29.46.66] (unassigned [217.29.46.66] (may be forged)) by hugo10.ka.punkt.de (8.14.2/8.14.2) with ESMTP id x2KNUA9q063833; Thu, 21 Mar 2019 00:30:46 +0100 (CET) (envelope-from hausen@punkt.de) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 12.2 \(3445.102.3\)) Subject: Re: bhyve and vfs.zfs.arc_max, and zfs tuning for a hypervisor From: "Patrick M. Hausen" In-Reply-To: <6388ebd5a12949179ff6da33eb107205@SERVER.ad.usd-group.com> Date: Thu, 21 Mar 2019 00:30:45 +0100 Cc: Victor Sudakov , "freebsd-virtualization@freebsd.org" Content-Transfer-Encoding: quoted-printable Message-Id: References: <20190319024638.GA8193@admin.sibptus.ru> <20190320015236.GA35511@admin.sibptus.ru> <6388ebd5a12949179ff6da33eb107205@SERVER.ad.usd-group.com> To: Matt Churchyard X-Mailer: Apple Mail (2.3445.102.3) X-Rspamd-Queue-Id: 81C00867B6 X-Spamd-Bar: --- Authentication-Results: mx1.freebsd.org; spf=pass (mx1.freebsd.org: domain of hausen@punkt.de designates 217.29.33.131 as permitted sender) smtp.mailfrom=hausen@punkt.de X-Spamd-Result: default: False [-3.15 / 15.00]; ARC_NA(0.00)[]; TO_DN_EQ_ADDR_SOME(0.00)[]; NEURAL_HAM_MEDIUM(-1.00)[-0.997,0]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[3]; R_SPF_ALLOW(-0.20)[+ip4:217.29.32.0/20]; MV_CASE(0.50)[]; MIME_GOOD(-0.10)[text/plain]; RCVD_TLS_LAST(0.00)[]; DMARC_NA(0.00)[punkt.de]; TO_DN_SOME(0.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; RCVD_COUNT_THREE(0.00)[3]; TO_MATCH_ENVRCPT_SOME(0.00)[]; MX_GOOD(-0.01)[cached: mailin.pluspunkthosting.de]; NEURAL_HAM_SHORT(-0.96)[-0.957,0]; RCVD_IN_DNSWL_NONE(0.00)[131.33.29.217.list.dnswl.org : 127.0.10.0]; IP_SCORE(-0.38)[ipnet: 217.29.32.0/20(-1.06), asn: 16188(-0.85), country: DE(-0.01)]; FROM_EQ_ENVFROM(0.00)[]; R_DKIM_NA(0.00)[]; MIME_TRACE(0.00)[0:+]; ASN(0.00)[asn:16188, ipnet:217.29.32.0/20, country:DE]; MID_RHS_MATCH_FROM(0.00)[] X-BeenThere: freebsd-virtualization@freebsd.org X-Mailman-Version: 2.1.29 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: Wed, 20 Mar 2019 23:30:49 -0000 Hi Matt, > Am 20.03.2019 um 10:34 schrieb Matt Churchyard = : >>> 2. If ARC does cache volumes, does this cache make sense on a=20 >>> hypervisor, because guest OSes will probably have their own disk = cache anyway. >>=20 >> IMHO not much, because the guest OS is relying on the fact that when=20= >> it writes it=E2=80=99s own cached data out to =E2=80=9Edisk=E2=80=9C, = it will be committed to=20 >> stable storage. >=20 > Maybe I've missed something but I don't quite get the link between = read cache (ARC) and guest writes here? You are correct - I confused ARC and ZIL. I still recommend to set sync=3Dalways for hypervisor =E2=80=9Edisk=E2=80=9C ZVOLs. Kind regards Patrick --=20 punkt.de GmbH Internet - Dienstleistungen - Beratung Kaiserallee 13a Tel.: 0721 9109-0 Fax: -100 76133 Karlsruhe info@punkt.de http://punkt.de AG Mannheim 108285 Gf: Juergen Egeling