From owner-freebsd-questions@FreeBSD.ORG Wed Jun 3 08:58:28 2015 Return-Path: Delivered-To: freebsd-questions@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:1900:2254:206a::19:1]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTPS id 79671A7F for ; Wed, 3 Jun 2015 08:58:28 +0000 (UTC) (envelope-from kraduk@gmail.com) Received: from mail-wi0-x235.google.com (mail-wi0-x235.google.com [IPv6:2a00:1450:400c:c05::235]) (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 0DD0C135F for ; Wed, 3 Jun 2015 08:58:28 +0000 (UTC) (envelope-from kraduk@gmail.com) Received: by wibut5 with SMTP id ut5so94930740wib.1 for ; Wed, 03 Jun 2015 01:58:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type; bh=4eojEij7fPtSfq9J2+9v5WNayifSxEzuNYeHgDWm1Jg=; b=JXg+4bcX2pKw3a4l8Qh8dYkSyUu8vyHUMHl80dnbvUx/WzrKcfvLi7Um+iY+kSx0IR Cv+f9uDm+w3rqnalZXmORI0A3HNMrb7ifVIWnoKkgT7N4MFKE4AUU4EJDF5tXpjxWGeZ k60JLPq6ABVJfJvZdkVg0kmsBSZea4/qhXxUBPCIfLl1kcgCJRcji8DRdjU/NS1eMJ1r HUp+SQ9QyEGOnapUVConBNVPfo3RDUMAgzNeemkmVDSG4mUHwDxQEQSnB6KEj299E4An T5j2Cuc+R4ngB80Fqj9uayis7089av7gB1V3wf10OJ/DKFk+nYUFCfXMGHEOw+xxzrkO TJTA== MIME-Version: 1.0 X-Received: by 10.194.62.132 with SMTP id y4mr59474596wjr.91.1433321906327; Wed, 03 Jun 2015 01:58:26 -0700 (PDT) Received: by 10.28.210.149 with HTTP; Wed, 3 Jun 2015 01:58:26 -0700 (PDT) In-Reply-To: <20150529133653.GA94981@neutralgood.org> References: <20150529092600.GA32731@ozzmosis.com> <20150529133653.GA94981@neutralgood.org> Date: Wed, 3 Jun 2015 09:58:26 +0100 Message-ID: Subject: Re: ZFS in a VM? From: krad To: kpneal@pobox.com Cc: andrew clarke , "freebsd-questions@freebsd.org" , Jaime Kikpole Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.20 X-BeenThere: freebsd-questions@freebsd.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: User questions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 03 Jun 2015 08:58:28 -0000 Strictly speaking its the online dedup that is expensive. Depending on your data sets and work patterns you can dedup a pool by doing things intelligently. eg use snap shots and clones where ever possible, if you have any out of hour periods, turn dedup on and rewrite all new data on the pool since the last dedup run (not a scrub). This is all getting off topic though. On 29 May 2015 at 14:36, wrote: > On Fri, May 29, 2015 at 07:26:01PM +1000, andrew clarke wrote: > > On Wed 2015-05-27 13:31:05 UTC-0400, Jaime Kikpole ( > jkikpole@cairodurham.org) wrote: > > > > > Can I run a FreeBSD system in a virtual machine and use ZFS? The VM > > > environment is a commercial system based on Linux's KVM, if that > > > matters. > > > > ZFS works better if it has "raw" access to the hard drive, in terms of > > performance and error detection, but will still work fine without it. > > Either way you'll still get all the usual features ZFS provides, such > > as snapshots, dedup, compression, etc. > > Strictly speaking, error detection itself doesn't work better with raw > disks. Error _correction_ works better with raw disks. Then again, this > is what the "copies=2" or "copies=3" option is for: to be able to correct > errors when ZFS is not handling the RAID or mirroring itself. > > > Keep in mind that large capacity ZFS datasets can require several GBs > > of memory to work well, particularly if you're using dedup, so you'll > > need to adjust your VM guest's memory appropriately. > > Be careful with dedup. The memory requirements are so large that with > large amounts of data is is easy to get into a situation that takes days > to recover from. > > When not using dedup: There are reports that ZFS can be used in as little > as 4GB of memory -- in the i386 FreeBSD at that! I've got a small setup > with 8GB of memory that works well for me, but I'm not using dedup until > I can put a lot more memory in this machine. > -- > "A method for inducing cats to exercise consists of directing a beam of > invisible light produced by a hand-held laser apparatus onto the floor ... > in the vicinity of the cat, then moving the laser ... in an irregular way > fascinating to cats,..." -- US patent 5443036, "Method of exercising a cat" > _______________________________________________ > freebsd-questions@freebsd.org mailing list > http://lists.freebsd.org/mailman/listinfo/freebsd-questions > To unsubscribe, send any mail to " > freebsd-questions-unsubscribe@freebsd.org" >