From owner-freebsd-fs@FreeBSD.ORG Thu Aug 29 21:56:46 2013 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [8.8.178.115]) (using TLSv1 with cipher ADH-AES256-SHA (256/256 bits)) (No client certificate requested) by hub.freebsd.org (Postfix) with ESMTP id 00CD764E for ; Thu, 29 Aug 2013 21:56:45 +0000 (UTC) (envelope-from fjwcash@gmail.com) Received: from mail-qc0-x234.google.com (mail-qc0-x234.google.com [IPv6:2607:f8b0:400d:c01::234]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by mx1.freebsd.org (Postfix) with ESMTPS id B56DA2D3A for ; Thu, 29 Aug 2013 21:56:45 +0000 (UTC) Received: by mail-qc0-f180.google.com with SMTP id l13so481293qcy.25 for ; Thu, 29 Aug 2013 14:56:44 -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=58BZGNunMJEKjfb5xK0lllAZdFvBhXjKVRPuGmSCOmY=; b=zNx2C2LhjJpbWWtGy8cogpDw/5Cv6fQPUo7QbFobpTzstjDJ7KAbNthPsvWKYp1CJi TRdCLDC3BDemEsvYEJoAW6wXkQF2HMmNGMEKjfTd+irfG7G4+2p/dneLrw9mnE/4NZvv qDW3s22GpAIeQGoLMl1poCr/mNOascy2zp3yJdienBZM+5vv4zkPmfi4E5Oy99C+q1AF hTl7GZ+CDsJg7fkyDyT1K+R3FJYxAyIJ1A7RjPsaDu3DUmO6JiNV2XXJ0luSTvL5FVsf 0GT5OW5/8lSWyijk4WXWf9Q4pduEhUcJ5xZ2ckIgWrzY9L8CTMSPpDIKtqMim/Wtx6vr Rs4w== MIME-Version: 1.0 X-Received: by 10.49.6.99 with SMTP id z3mr6658524qez.27.1377813404857; Thu, 29 Aug 2013 14:56:44 -0700 (PDT) Received: by 10.49.1.98 with HTTP; Thu, 29 Aug 2013 14:56:44 -0700 (PDT) In-Reply-To: <877gf4cj7o.wl%berend@pobox.com> References: <1079189088.15197172.1377784177805.JavaMail.root@uoguelph.ca> <877gf4cj7o.wl%berend@pobox.com> Date: Thu, 29 Aug 2013 14:56:44 -0700 Message-ID: Subject: Re: NFS on ZFS pure SSD pool From: Freddie Cash To: Berend de Boer Content-Type: text/plain; charset=UTF-8 X-Content-Filtered-By: Mailman/MimeDel 2.1.14 Cc: FreeBSD FS X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 29 Aug 2013 21:56:46 -0000 On Thu, Aug 29, 2013 at 1:53 PM, Berend de Boer wrote: > >>>>> "Freddie" == Freddie Cash writes: > > Freddie> This will show you how many bytes of the ARC are being > Freddie> used by metadata: sysctl vfs.zfs.arc_meta_used > > Freddie> You can tune what the max is via: sysctl > Freddie> vfs.zfs.arc_meta_limit > > Strangely enough on my system arc_meta_used = 2GB, while > arc_meta_limit = 1.5G. > > Wouldn't you expect that arc_meta_used would be lower than this limit? > You would think so. Maybe this is not a hard limit, but a high-water mark that leads to an eviction process running? Don't know, I'm not at all versed in the inner workings of ZFS. :) I do know other vfs.zfs.*limit tunables were high-water marks and work was underway to turn them into hard limits. Maybe this needs to be added to that list? Maybe it's not worth worrying about? -- Freddie Cash fjwcash@gmail.com