From owner-freebsd-scsi@FreeBSD.ORG Thu Mar 18 16:07:31 2010 Return-Path: Delivered-To: scsi@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id 4C847106564A for ; Thu, 18 Mar 2010 16:07:31 +0000 (UTC) (envelope-from glen.j.barber@gmail.com) Received: from mail-gx0-f214.google.com (mail-gx0-f214.google.com [209.85.217.214]) by mx1.freebsd.org (Postfix) with ESMTP id 091E38FC0C for ; Thu, 18 Mar 2010 16:07:30 +0000 (UTC) Received: by gxk6 with SMTP id 6so1536055gxk.14 for ; Thu, 18 Mar 2010 09:07:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:received:received:date:from:to:subject :message-id:mime-version:content-type:content-disposition:user-agent; bh=WtO6bfDA8EvFvlLz97UNk1G/aaeJAqBWQZKyXumi3eo=; b=BZaTlWFVkwtwXcqkmy4UJwqRVo+o6FaW6miuKR1A2CK2hh1PYB2VN9WWJq4jQlngXf ig1FcE8kqgqbWwtj6eROnjTeRl5+7VEH7zPjSvi2Z6XoeiMEZBtQlxjDJnozFgmq4sMf mVIy1kYWGCumrZTsOO6bdxg+6fzJk8IpnpX8c= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=date:from:to:subject:message-id:mime-version:content-type :content-disposition:user-agent; b=sNqu8VFCrr7UPj6Pto83fG567xFclQ/hUjHRoqosd1JPecJHypNOGLe6XuVYW4kl8w vzlU6mJyvCbGC8UuV89ZqbgdhFqy/yGZjTKdXJZ+/qqNvojCEMh6ghoTTCimfCQAOOUv SYnWhYzgXHSDoFkvytXCOTYGnAqx3C0PypdGk= Received: by 10.102.169.39 with SMTP id r39mr9213815mue.126.1268927101386; Thu, 18 Mar 2010 08:45:01 -0700 (PDT) Received: from orion.hsd1.pa.comcast.net (c-71-230-240-241.hsd1.pa.comcast.net [71.230.240.241]) by mx.google.com with ESMTPS id 12sm518232muq.31.2010.03.18.08.44.59 (version=SSLv3 cipher=RC4-MD5); Thu, 18 Mar 2010 08:45:00 -0700 (PDT) Date: Thu, 18 Mar 2010 11:41:38 -0400 From: Glen Barber To: scsi@freebsd.org Message-ID: <20100318154138.GA30096@orion.hsd1.pa.comcast.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline User-Agent: Mutt/1.5.20 (2009-06-14) Cc: Subject: Optimum dev_openings value X-BeenThere: freebsd-scsi@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: SCSI subsystem List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 18 Mar 2010 16:07:31 -0000 Hi, I have three machines running 8.0-RELEASE, each with two mirrored Seagate SCSI disks using ZFS. In making sure these machines are performing as best as possible, I'm trying to find what the best practices are with regards to dev_openings values, and what determines the default dev_openings value. Two machines have identical ahc(4) Adaptec AIC7899 Ultra160 SCSI adapters, but display different defaults, which I have not had luck finding an explanation: h04# camcontrol tags da0 -v (pass0:ahc1:0:0:0): dev_openings 33 (pass0:ahc1:0:0:0): dev_active 0 (pass0:ahc1:0:0:0): devq_openings 33 (pass0:ahc1:0:0:0): devq_queued 0 (pass0:ahc1:0:0:0): held 0 (pass0:ahc1:0:0:0): mintags 2 (pass0:ahc1:0:0:0): maxtags 255 h21# camcontrol tags da0 -v (pass0:ahc0:0:0:0): dev_openings 64 (pass0:ahc0:0:0:0): dev_active 0 (pass0:ahc0:0:0:0): devq_openings 64 (pass0:ahc0:0:0:0): devq_queued 0 (pass0:ahc0:0:0:0): held 0 (pass0:ahc0:0:0:0): mintags 2 (pass0:ahc0:0:0:0): maxtags 255 h04# camcontrol devlist at scbus1 target 0 lun 0 (pass0,da0) at scbus1 target 1 lun 0 (pass1,da1) h21# camcontrol devlist at scbus0 target 0 lun 0 (pass0,da0) at scbus0 target 1 lun 0 (pass1,da1) Is there an obvious explanation for the difference here? The third machine uses sym(4), which I expect would cause a different default dev_openings (currently defaulted to 44). Is there a general rule to adjusting this value? -- Glen Barber