From owner-freebsd-hackers@FreeBSD.ORG Wed Jan 16 07:48:26 2013 Return-Path: Delivered-To: freebsd-hackers@freebsd.org Received: from mx1.freebsd.org (mx1.FreeBSD.org [8.8.178.115]) by hub.freebsd.org (Postfix) with ESMTP id 690EFFB3 for ; Wed, 16 Jan 2013 07:48:26 +0000 (UTC) (envelope-from dieterbsd@gmail.com) Received: from mail-ia0-x231.google.com (mail-ia0-x231.google.com [IPv6:2607:f8b0:4001:c02::231]) by mx1.freebsd.org (Postfix) with ESMTP id 44BD4FD3 for ; Wed, 16 Jan 2013 07:48:26 +0000 (UTC) Received: by mail-ia0-f177.google.com with SMTP id h8so96715iaa.22 for ; Tue, 15 Jan 2013 23:48:26 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:x-received:date:message-id:subject:from:to :content-type; bh=UMWpVG3H/cYmVwNqF5ctGHSxfBri8csGcfbbvpklgz4=; b=SHBneURVTB7yV1qV8Fgp4nefGkiYRjEoy2mmo7l20GVYKVNNgSX0ULkH6jZRMkPC28 PvXJcB4VtSoswbob69YxAWs3SKUucOgoSh/myncDaX6n7gwgztnplN9VsE4Klr4h+S7E +jwo53lpA6r7vGJawMJGdOb0q0lt4LvhMTY8RMyOb3647hiTXOcHRF1cdfZYJa9aY82e 5oozb4QHkpeYBGt5l1tJR397NlIz07oFdbkMj0NCD67C6PlM7hHBEBQ3nf2qKcPKQMF2 iCh+l7vYg4AbWdMPj2Y8iCkQTD3MXs9Mf7jdezu9skdDysvvt25i2RFwZ0u+E7R31LSo vtyA== MIME-Version: 1.0 X-Received: by 10.50.159.165 with SMTP id xd5mr105010igb.82.1358322506005; Tue, 15 Jan 2013 23:48:26 -0800 (PST) Received: by 10.64.107.196 with HTTP; Tue, 15 Jan 2013 23:48:25 -0800 (PST) Date: Tue, 15 Jan 2013 23:48:25 -0800 Message-ID: Subject: Re: IBM blade server abysmal disk write performances From: Dieter BSD To: freebsd-hackers@freebsd.org Content-Type: text/plain; charset=ISO-8859-1 X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 16 Jan 2013 07:48:26 -0000 Karim writes: > It is quite obvious that something is awfully slow on SAS drives, > whatever it is and regardless of OS comparison. We swapped the SAS > drives for SATA and we're seeing much higher speeds. Basically on par > with what we were expecting (roughly 300 to 400 times faster then what > we see with SAS...). Major clue there! According to wikipedia: "Most SAS drives provide tagged command queuing, while most newer SATA drives provide native command queuing" [1] Note that the driver says "Command Queueing enabled" without specifying which. If the driver is trying to use SATA's NCQ but the drive only speaks SCSI's TCQ, that could explain it. Or if the TCQ isn't working for some other reason. See if there are any error messages in dmesg or /var/log. If not, perhaps the driver has extra debugging you could turn on. Get TCQ working and make sure your partitions are aligned on 4 KiB boundaries (in case the drive actually has 4 KiB sectors), and you should get the expected performance. [1] http://en.wikipedia.org/wiki/Serial_attached_SCSI