From owner-freebsd-fs@FreeBSD.ORG Tue Oct 16 11:25:59 2012 Return-Path: Delivered-To: freebsd-fs@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id E0A5A9AD for ; Tue, 16 Oct 2012 11:25:59 +0000 (UTC) (envelope-from olivier@gid0.org) Received: from mail-lb0-f182.google.com (mail-lb0-f182.google.com [209.85.217.182]) by mx1.freebsd.org (Postfix) with ESMTP id 5D1AB8FC1B for ; Tue, 16 Oct 2012 11:25:58 +0000 (UTC) Received: by mail-lb0-f182.google.com with SMTP id b5so5131043lbd.13 for ; Tue, 16 Oct 2012 04:25:57 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20120113; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding:x-gm-message-state; bh=JWS/1ekXrQFiJnhTiHCvBmdmKhEoOjmikFgVYfQtHgw=; b=EVt1SGcubsOIe+8uCk6oEqAlhqOdZ/qSs8VPUDrXX6nF93RvKZlR9fyrZRwoe7G1OS GcOjLpm2aFkq2MQLib/RFkrg0+6od1kpUvcPkEWe3MqnzDTKH0k0HuVLuurRSjhGYFDe ZOr8PuW26kr/Z2MpnsX/Kg8GYAHEGM90X1fWWA6vOCnF64fYU6mm8UPkv9UC3EGSGHWo m3O3bj3fLAxM8GLhY/FHSPcIdHWRcPPqrhQQZG/vhm14uxJu1tk3CaFmL+XzIPtGMVqM rfPGoHSOaFeBDZrpUcaAZcr/jWe1FyynxVD7UtSF9Dqs7+adXvBJmi5OFe9U262SLq9A A8PQ== MIME-Version: 1.0 Received: by 10.112.45.231 with SMTP id q7mr5380448lbm.133.1350386757796; Tue, 16 Oct 2012 04:25:57 -0700 (PDT) Received: by 10.112.87.202 with HTTP; Tue, 16 Oct 2012 04:25:57 -0700 (PDT) In-Reply-To: <6116A56E-4565-4485-887E-46E3ED231606@ebureau.com> References: <6116A56E-4565-4485-887E-46E3ED231606@ebureau.com> Date: Tue, 16 Oct 2012 13:25:57 +0200 Message-ID: Subject: Re: Imposing ZFS latency limits From: Olivier Smedts To: Dustin Wenz Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable X-Gm-Message-State: ALoCoQl0YmwBT3v/aWwKEcjlgApltKCn7FHI2iWdE4F1Zq5BFw5B/BqIPPVNswO8BshZGSKjBr4s Cc: freebsd-fs@freebsd.org 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: Tue, 16 Oct 2012 11:25:59 -0000 2012/10/8 Dustin Wenz : > I'm trying to find a way to get lower read latency in ZFS when there is a= failing disk in a mirror. The specific failure mode that I'm trying to han= dle is when a disk takes significantly longer than usual to respond to read= requests, but is not so far gone that the OS drops it from the bus. In tha= t case, the whole pool can become much less responsive than I think it need= s to be. > > Since ZFS has access to the data I'm reading through other members in a m= irror, I would like ZFS to defer to the redundant disks when individual dis= k latency exceeds some threshold that I would define. Is there any provisio= n for this in the FreeBSD ZFS implementation? That would be great - no need for TLER drives. But if you want to "drop" the drive from the bus, that would be a GEOM thing. Don't know if that's possible to implement. --=20 Olivier Smedts _ ASCII ribbon campaign ( ) e-mail: olivier@gid0.org - against HTML email & vCards X www: http://www.gid0.org - against proprietary attachments / \ "Il y a seulement 10 sortes de gens dans le monde : ceux qui comprennent le binaire, et ceux qui ne le comprennent pas."