On 17 Mar, Jeff Waugh wrote: > <quote who="[EMAIL PROTECTED]"> > > > 1) Why do you need a ram disk if raid1 and ext3 are not modules, but > > actually compiled into the kernel? > > You don't. :)
Ah, good. > > 2) If you have a separate ext2 partition for /boot, do the modules have > > to be there too? (Or are you expected to use an initrd then?) > > No on both counts. Okay. > > 3) What is /initrd for, anyway? Why does that empty directory exist at > > all? > > It's there if you want to move the initrd's root somewhere after you mount > the new (real) root filesystem. Generally you just unmount it anyway. So it's a mount point for it, just in case for some reason you still wanted it around. Okay, makes sense. > > 4) Where did Red Hat get there jbd.o module from? My 2.4.17 kernel > > source doesn't have that as an option. It's either built in, or not > > there at all. > > No idea what Red Hat do with their kernels. :-) > > > Mirroring root is OK. You just need to put /boot somewhere else. > > > > It still seems strange that using RAID to mirror root is a bad idea, > > since it seems to me that raid1 was designed for mirroring file systems > > in the first place (especially root)! And it seems even stranger to > > recommend that mirroring it manually, on the other hand, is good. > > Not really; this is software RAID, and you're competing with a different > class of problems to hardware RAID. Especially when you start bringing > modules loaded from "a filesystem" (could be initrd, could be root) into the > equation. > > Herbert is right, but I'm slightly more conservative, so I keep a minimal > root/boot partition, and have everything elsewhere. Basically, my data > matters, my software doesn't. I can rebuild or mirror it easily enough. Ah, okay. I have a bigger / file system, so consequently I really don't want to lose that, nor all the configuration that I've done, and all the extra rpm file installed, etc. When I smashed my system with Ximian recently, it took me many nights to get everything set up the way I like it again, after the 7.2 install. > > I'd honestly like to know more details about why some people recommend > > against using raid on the root file system. > > What does it gain you? What pain do you have to go through to use it > (barring nice RAID installers like Red Hat's)? Not pain, but some confusion maybe? But I'm happy to learn about setting up raid devices, and turning them off, etc. > What pain do you have to go > through to recover or fix it? Well, if one disk fries one day, then I guess I'll find out. > Why expend these resources on something far > less critical (and simpler to replace) than your data? See above. Basically, lots of configuration is so smeared out that it's a laborious process to recover it all. > > Do I need to have /lib/modules on the same /boot partition? (If I > > don't, aren't I going to have just the same problem with finding the > > modules before the filesystem is mounted?) > > No. /boot holds your kernels. If those kernels have RAID built in, or > include initrd images, they will let you use RAID on any subsequent mounts. Right. So I should change /boot to be on my new samll ext2 file system. > I always set my software RAID paritions up to autodetect, and have RAID > stuff built into the kernel. So much hassle avoided. That's basically what I have too. Funnily enough, I discovered that the RAID autodetect is almost too good. I was stunned to see the /dev/md1 I was using for swap come back into existence after a reboot. It was because I hadn't written the partition table out before exiting fdisk. Fortunately the /etc/raidtab and /etc/fstab were correct, so nothing crazy happened. I just had to break it up again. > > Fortunately, juggling kernel configs is trivial with the Tk/Tcl mods to > > the xconfig's scripts that I mailed a while back. > > "cp <blah> .config" works pretty well too. :) Yeah, but when you have 20 or 30 configs, with long meaningful names, so that you know what each one is, and what you were experimenting with, it can be a lot of typing. :-) > G'luck! > > - Jeff Thanks for all that good info and advice, Jeff. Everything seems well now, so I think I'll call it a night. I strongly suspect that the mistake I was making all along was not compiling in ext3 filesystem support at all! I guess I misread "ext3 journalling filesystem EXPERIMENTAL" as `ext3-journalling filesystem' instead of `ext3 journalling-filesystem', and I assumed that ext3 was so like ext2, it was just always built in, and didn't even appear anywhere as an option. (At least, that's how I reconstruct my strange mental processes in this case. D'oh!) luke -- SLUG - Sydney Linux User Group Mailing List - http://slug.org.au/ More Info: http://lists.slug.org.au/listinfo/slug
