From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stefan Richter Subject: Re: [PATCH] USB: storage: add "no SYNCHRONIZE CACHE" quirk Date: Fri, 26 Jun 2015 13:05:05 +0200 Message-ID: <20150626130505.3918c5a9@kant> References: <1434994588.2237.90.camel@HansenPartnership.com> <20150626114308.7b5b8006@kant> <1435313657.2211.70.camel@HansenPartnership.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Return-path: Received: from einhorn.in-berlin.de ([192.109.42.8]:55437 "EHLO einhorn.in-berlin.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751680AbbFZLGB (ORCPT ); Fri, 26 Jun 2015 07:06:01 -0400 In-Reply-To: <1435313657.2211.70.camel@HansenPartnership.com> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: James Bottomley Cc: Alan Stern , Greg KH , James Bottomley , Jun Itou , Markus Rathgeb , Matt , SCSI development list , USB Storage list , USB list , Jens Axboe On Jun 26 James Bottomley wrote: > On Fri, 2015-06-26 at 11:43 +0200, Stefan Richter wrote: > > On Jun 22 James Bottomley wrote: [...] > > > Perhaps it might be wise to do this to every USB device ... for external > > > devices, the small performance gain doesn't really make up for the > > > potential data loss. > > > > Just a small note on the assumption of externally (and in extension, > > temporarily) attached devices: Not all USB-attached devices are external, > > and not all external devices are used as removable devices. > > The problems don't depend on the connection type: internal devices which > have a writeback cache and don't accept flush commands have data > integrity problems too. I can't really think of many situations where > you'd be willing to sacrifice data integrity for performance. Sure; writeback caches are prone to more issues besides sudden connection loss. (E.g. sudden power loss is but one of several more potential issues of course.) I merely wanted to remind that the bus type of a device (USB or whatever) does not say much about the risk of sudden connection loss to that device, since such devices may have physical protection against sudden connection loss too. I was not particularly commenting on the topic at hand, i.e. on presence of writeback cache without working flush command. -- Stefan Richter -=====-===== -==- ==-=- http://arcgraph.de/sr/