LVM gives you the option of swapping around the device numbers transparently too. It will alway be able to build the volumes, even if the nodes change. Red Hat also, by convention, sets up everything to mount by label, giving the same flexibility to non-LVM devices. The only one that NEEDS to be on a particular address is the one you boot from.
-----Original Message----- From: Linux on 390 Port [mailto:linux-...@vm.marist.edu] On Behalf Of Scott Rohling Sent: Monday, February 23, 2009 9:31 AM To: LINUX-390@VM.MARIST.EDU Subject: Re: [LINUX-390] Why does one need to mkinitrd/zipl ? (WAS : Broken logical volume group) Good point.. I've always advised giving ranges in modprobe.conf and allowing for growth so you don't have to worry about initrd in most cases. Also - use the ranges as an indicator of what's there.. example: 100 -- /boot 101-110 -- swap 120-130 -- OS disks ( / ) - LVMs for the base OS 200-21F -- Application code LVMs, config, etc (often mounted /opt) 300-31F -- Data (database LVMs, whatever) Things often don't break down in such clean lines - but you get the idea. One advantage is that if you are dealing with LVMs -- and need to do some recovery -- you know by the ranges which disks you'll need to get to make sure you have all the disks for the Linux system LVMs you're trying to fix. I'm sure there are similar schemes buried in the archives, too ;-) Scott On Mon, Feb 23, 2009 at 7:11 AM, Hall, Ken (GTS) <ken_h...@ml.com> wrote: > If this was covered in previous notes, sorry, but I didn't see it, and > I've been out for a few days so I didn't get into this at the beginning. > > In Red Hat (and probably Suse too), there's a chicken-egg problem. The > DASD driver gets its list of valid devices from a parm that's passed to > the driver in /etc/modprobe.conf. But at the time the module is loaded, > the running root filesystem is the initrd. The regular root filesystem > can't be mounted till AFTER the dasd driver is loaded. You only need to > make the initrd if you change the list of devices. > > We coded a list of placeholder device numbers in our base configuration > going out to dasdzz, so we don't have to fiddle going forward. Note > that this list is ONLY devices that are visible automatically at boot > time, and reserves the device node assignments for them. Additional > devices outside the range can be added later via attach and chccwdev, > and device nodes will be built starting after the list built from the > parameter. (i.e., if modprobe.conf contains 100-10F, that reserves > dasda-dasdp, even if some of them don't exist, and the first dynamically > added disk will be dasdq.) > > As far as bare metal goes, we did try some tests in a bare LPAR, and it > works fine with thousands of devices visible, but it takes a LONG time > to scan them all. Also, at the time we tested, there was some quirk > with coding the actual devices in modprobe.conf, and filtering that way > caused the system to hang coming up. It might have been an error in > configuration somewhere, we were on a schedule, so we simply removed the > filter, and brought it up seeing all devices. > > -----Original Message----- > From: Linux on 390 Port [mailto:linux-...@vm.marist.edu] On Behalf Of > Ivan Warren > Sent: Thursday, February 19, 2009 9:37 AM > To: LINUX-390@VM.MARIST.EDU > Subject: Re: [LINUX-390] Why does one need to mkinitrd/zipl ? (WAS : > Broken logical volume group) > > Richard Troth wrote: > > Ivan ... hear this: > > With SLES10, unless you are changing something about the root FS, you > > do not need to re-stamp your INITRD. It is exactly as you say it > > should be. > > > > > > -- R; <>< > > > > > That's good enough for me ;) > > At least the idea that I would have gave me fodder for a tantrum :P > > --Ivan > > ---------------------------------------------------------------------- > For LINUX-390 subscribe / signoff / archive access instructions, > send email to lists...@vm.marist.edu with the message: INFO LINUX-390 or > visit > http://www.marist.edu/htbin/wlvindex?LINUX-390 > > ------------------------------------------------------------------------ -- > This message w/attachments (message) may be privileged, confidential or > proprietary, and if you are not an intended recipient, please notify the > sender, do not use or share it and delete it. Unless specifically indicated, > this message is not an offer to sell or a solicitation of any investment > products or other financial product or service, an official confirmation of > any transaction, or an official statement of Merrill Lynch. 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