From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mike Anderson Subject: Re: [RFC] Persistent naming of scsi devices Date: Wed, 10 Apr 2002 10:45:50 -0700 Sender: linux-scsi-owner@vger.kernel.org Message-ID: <20020410104550.A9957@beaverton.ibm.com> References: <20020410091918.C546@thunk.org> <200204101405.KAA09838@hancock.sc.steeleye.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Content-Disposition: inline In-Reply-To: <200204101405.KAA09838@hancock.sc.steeleye.com>; from Eddie.Williams@steeleye.com on Wed, Apr 10, 2002 at 10:04:01AM -0400 List-Id: linux-scsi@vger.kernel.org To: Eddie Williams Cc: Theodore Tso , "Martin K. Petersen" , linux-scsi@vger.kernel.org Eddie Williams [Eddie.Williams@steeleye.com] wrote: > On Wednesday 10 April 2002 09:19 am, Theodore Tso wrote: > > > That is indeed a hard problem, and ultimately, the thing that will > > make this easier is if there's some way we can read out a > > drive-specific serial number out of the ATAPI or SCSI interfaces. I > > don't know if disk serial numbers are commonly supported by disk > > manufacturers, but hopefully the newer disks have something like that > > we can use. Without it, though, the problem is very, very hard if you > > want to make it 100% foolproof --- and hence, something which > > civilians (i.e., stupid users) can use. > > While I enjoy bashing stupid users I would like to point out that persistent > naming, while it makes life easier for stupid users, it has tremendous > benefits for all of us. > > We (the product I work on) have used serial numbers for a long time to > uniquely identify devices and this improves the ease of use tremendously. In > a cluster this is really critical or one can easily try to bring an > application in-service on a wrong device with catestrophic results. Agreed, While the immutablity / uniqueness of uuids across different name spaces may vary depending on device capability there are still useful. Many have been obtaining IDs from devices for years using a method of obtaining the most unique ID the device can provide and then ensuring that names spaces do not collide (i.e go for page 0x83, then 0x80, vendor-product-serial, vendor unique). We have also found in the past that when users make complete copies of there volumes (for the purpose of hot-backup) that a uuid is one of the few methods that can be used to differ the clone from the original. -Mike -- Michael Anderson andmike@us.ibm.com