From mboxrd@z Thu Jan 1 00:00:00 1970 From: Nicholas Henke Date: Wed, 25 Mar 2009 15:15:59 -0500 Subject: [Lustre-devel] Start the MGS first? In-Reply-To: <49CA8A73.9080103@sun.com> References: <49CA8A73.9080103@sun.com> Message-ID: <49CA90FF.1070801@cray.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: lustre-devel@lists.lustre.org Nathaniel Rutman wrote: > As of Lustre 1.6, servers can be started in any order (after the initial > registration at first startup). Internally, this required significant > bending of our connection rules, and with a move toward ZFS becomes even > more burdensome. So my question to the Lustre community is this: would > anyone strenuously object to a startup ordering requirement that the MGS > must be started before any other servers? This would probably be in the > Lustre 3.0 timeframe. It is also likely that we will have to divorce > the MGS and MDT onto separate devices -- no more "combo" MDT/MGSes. >> > NR> I think the only reason to have a local config file is to be >> able to >> > NR> start a server in the absence of the MGS. How much effort do >> we want >> > NR> to expend to be able to keep that ability? I don't think it's >> a huge >> > NR> burden to say "MGS must be started first". > This is virtually ensured today due to how the timeouts and ordering works. 1) It is a real PITA to script up different server start orders to deal with reformat and write_conf. It is easier to just script one correct way of doing this - KISS if you will. 2) At large scale, the timeout cascading on the OSTs (many OSTs per OSS) from a missing MGS requires it be started first. 3) With bug 14134 and --nomgs and --nosvc options for starting, it makes starting a combo MGS and MDS "correctly" much easier. Nic