From mboxrd@z Thu Jan 1 00:00:00 1970 From: Luben Tuikov Subject: Re: generating a Linux WWN? Date: Mon, 8 Oct 2007 11:34:43 -0700 (PDT) Message-ID: <962818.30064.qm@web31813.mail.mud.yahoo.com> References: <47079D64.3070000@garzik.org> Reply-To: ltuikov@yahoo.com Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7BIT Return-path: Received: from web31813.mail.mud.yahoo.com ([68.142.207.76]:24433 "HELO web31813.mail.mud.yahoo.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1754793AbXJHSep (ORCPT ); Mon, 8 Oct 2007 14:34:45 -0400 In-Reply-To: <47079D64.3070000@garzik.org> Sender: linux-scsi-owner@vger.kernel.org List-Id: linux-scsi@vger.kernel.org To: Jeff Garzik , James Bottomley Cc: David Miller , ltuikov@yahoo.com, lydianconcepts@gmail.com, mdr@sgi.com, James.Smart@emulex.com, linux-scsi@vger.kernel.org --- Jeff Garzik wrote: > James Bottomley wrote: > > My problem with auto generated is that it's provably impossible to > > generate globally unique numbers for WWNs without some internal source > > of uniqueness (I know sparcs have this in their serial number, but most > > PCs unfortunately don't). > > > > I know the auto generated number can be statistically reasonably unique, > > but sysadmins are lazy people. If they run into this problem, they'll > > take the knob with the on/off switch rather than the think about the > > problem and specify the full WWN; and then, being busy people, they'll > > forget about it as "problem solved". When they do this, statistically > > (and probably years later) there will be a cluster reboot where the > > entire SAN simply collapses and no-one knows why ... the poor SAN > > administrator will likely spend weeks working out the problem is. > > Why, if we give lazy administrators root access, that's all they'll use, > and they will just think "problem solved" until a serious security issue > arises that takes down the cluster. > > See how silly and un-Linux that logic is? In Linux, the admin has the > power to make stupid decisions -- or to make informed decisions that > disagree your rigid "an admin should never do that" line of thought. > It's their hardware. > > You're also using the 1% case of a 1% case of a 1% case to argue against > a feature that is useful in making things Just Work(tm). What he's arguing about is the _capability_ for a node in a SAN to *(auto)generate* WWN and assign it to itself (at every reboot, etc). This is considered a _rogue_ node and *no* SAN architect or admin will tolerate such a node. The problem here is NOT the _capability_ to assign a WWN. Admin does have the capability to assign (if missing) and/or override (if present) a WWN currently with aic94xx driver. This is fine. The problem is "(auto)generate". Think of SANs. Luben