From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: util-linux-owner@vger.kernel.org Received: from aserp1040.oracle.com ([141.146.126.69]:44131 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751091AbbFRVB3 (ORCPT ); Thu, 18 Jun 2015 17:01:29 -0400 To: Tom Yan Cc: "Martin K. Petersen" , linux-scsi@vger.kernel.org, Karel Zak , util-linux@vger.kernel.org, linux-usb@vger.kernel.org Subject: Re: optimal io size / custom alignment From: "Martin K. Petersen" References: <20150615133154.GV1992@ws.net.home> Date: Thu, 18 Jun 2015 17:01:19 -0400 In-Reply-To: (Tom Yan's message of "Wed, 17 Jun 2015 17:49:51 +0800") Message-ID: MIME-Version: 1.0 Content-Type: text/plain Sender: util-linux-owner@vger.kernel.org List-ID: >>>>> "Tom" == Tom Yan writes: Tom> No I put it in the wrong way. What I meant was "sd vs md". For Tom> example, couldn't the scsi disk driver bind the value it reads from Tom> the VPD to another variable instead of "optimal i/o size", so that Tom> this value would be exclusively for RAID (and other virtual Tom> devices)? Who says that RAID is a virtual device? Hardware RAID controllers as well as SAS, iSCSI and Fibre Channel disk arrays all use the Block Limits VPD to communicate their preferred I/O size and alignment to us. As do enterprise disk drives. We deal with broken devices by blacklisting them. I suggest you try to find a way we can reliably identify your UAS devices. If there is a common pattern, we can entertain adding a workaround. -- Martin K. Petersen Oracle Linux Engineering