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Kevin Hanson <tuxpert@×××××××.net> posted 45C92BFC.2020503@×××××××.net, |
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excerpted below, on Tue, 06 Feb 2007 19:31:40 -0600: |
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|
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>> Did you look in to EVMS at all. I am setting up a similar system to |
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>> yours...4 stat disk, linux raid, etc. However, I really wanted to use |
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>> EVMS and am only partially successful. I have, as of now, been able |
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>> to get the EVMS stuff correctly in initrd such that I can complete a |
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>> boot. |
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>> |
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>> Just curious if you'd looked into EVMS at all and if you had any |
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>> thoughts. |
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|
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> Wow...I didn't type well in the above message...it's supposed to be |
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> 'sata' not 'stat' disk... |
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> And I was trying to say "I have, as of now, NOT been able...." |
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|
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It seems to be going around. =8^( |
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|
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[I'm adding this after typing the below. It occurs to me I might be |
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discussing everything /except/ what you need. If so, I'm sorry. I'm |
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posting this however, in case it can do /someone/ some good, even if |
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that's not you. Hopefully it helps you too, but if not, after putting all |
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this effort into it, I hope it helps /someone/. =8^) ] |
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|
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I haven't looked into EVMS, no. However, as I understand it, while EVMS |
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and LVM2 were at one time built on different kernel mechanisms, when LVM2 |
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was selected for merging into the mainline kernel (2.5 era I believe, |
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2002), EVMS decided rather than fight it, to take their already great |
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management tools and make them work with the LVM2 framework as it was |
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merged into the kernel. =8^) Thus, I believe EVMS is now simply what |
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amounts to a GUI front-end to the LVM2 system as it exists in the kernel |
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and lower level command-line tools. |
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|
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If it's not working for you, presumably the issue is that something isn't |
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configured right in the lower level LVM2 layer. Sometimes you just gotta |
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dive in and get your hands dirty at the command line level to most |
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efficiently figure out what's going wrong, and this would appear to be one |
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of those times. You may or may not eventually figure out the issue at the |
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higher level, but once you understand what's going on at the lower level |
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and fix the problem, I'm guessing you should be able to go right back to |
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using your higher level interface for routine work, if so desired. |
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|
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My approach was to take one thing at a time. First I studied RAID and |
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mdadm and got how it worked figured out at least enough to design the |
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system I wanted at that level. Then I did the same with LVM2. Honestly, |
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I was aware of the EVMS thing, but had forgotten the details, and it never |
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occurred to me to try it since I was under the impression that they had |
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lost out (they did with their lower layers, but just took their strengths, |
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the upper layers, and refitted them to the LVM2 framework, actually a |
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rather cool thing to do IMO) and were no longer a mainline Linux project |
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(I was wrong there, since they continued with their GUI front-end, just |
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built on LVM). |
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|
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Actually, I had another thing to learn as well. When I started on Linux |
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using Mandrake, GRUB was far less mature and I learned LILO. When I |
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transferred to Gentoo, I just continued using LILO, for awhile just using |
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the Mandrake executable on Gentoo, even. Since I was setting up an |
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entirely new RAID system anyway, and already learning it and LVM2, I |
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decided it was time to bite the bullet and learn and switch to GRUB as |
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well, so I learned it too. =8^) |
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|
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Then after I actually got an overview of how it all fit together, and had |
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designed my system at that level so I could actually start working with |
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it, I retraced the same steps only this time actually getting the |
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operational detail and putting it into practice as I went. Partitioned |
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RAID in particular, however, never /was/ entirely clear to me, until I |
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started actually doing it. That was mainly because it was new enough that |
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there were tantalizing mentions of it, but not the direct coverage of |
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every aspect of it, both theory and step-by-step, that I was able to get |
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with RAID and LVM2 in general, using mainly the three sources of each ones |
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HOWTO, together with the Gentoo LVM and RAID documentation. |
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|
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Since I already knew I didn't want LVM2 on my root partitions, because |
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that would require the additional complexity of an initramfs and I wanted |
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to retain direct-kernel-boot, I was able to (1) do the physical drive |
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partitioning (no problem, I'd done that many times over the years), (2) |
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create and assemble the RAID-1 for /boot, (3) while still booting from my |
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separate single drive (legacy PATA), play with that until I got the |
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practical knowledge of how to actually get the kernel to see and assemble |
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the RAID, (4) while still booting from the separate disk, figure out how |
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to mkfs the assembled RAID-1, (5) still booting from the separate disk, |
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install the kernel and grub to the new RAID-1, (6) still booting the |
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separate disk, figure out how to get GRUB installed on the physical boot |
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sectors of ALL FOUR physical disks, (7) NOW figure out how to actually |
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boot grub from any of the four, and verify that it actually worked as I |
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intended, (8) get the GRUB config and kernel command line correct to |
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actually get from GRUB into a kernel installed on that RAID-1 /boot. (9) |
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NOW with the RAID-1 working and actually booting to the root on my |
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existing single drive, figure out the partitioned RAID-6 for the root |
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filesystems and LVM2 partition (this started to get easier since now I |
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only had to learn the difference between RAID-1 and RAID-6, and between |
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partitioned and non-partitioned RAID, I already had practical knowledge of |
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working with RAID in general using mdadm), (10) verify that there were |
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indeed no weird tricks to partitioned RAID I hadn't considered, and |
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actually partition the RAID-6 using cfdisk, (11) not yet quite believing |
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it could actually be this simple (but it was), since this hadn't been |
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covered so well in the documentation since partitioned RAID was so new, |
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mkfs the partitioned RAID-6 partitions, (12) mirror my existing root file |
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system off the legacy PATA drive onto the two RAID-6 root partitions, once |
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to each, working and backup, (13) figure out how to get GRUB to point the |
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kernel at these new partitions for its root, (14) actually boot into the |
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new partitions and see that everything so far was working. |
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|
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Only at THAT point did I even START to consider the practical knowledge of |
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the LVM2 stuff. At that point, I had verified working partitioned RAID-6, |
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as I was booting into it as my root filesystem, so I knew at least to that |
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point, everything HAD to be working, since I'd not be able to boot into it |
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if not! Again, the lower complexity of the partitioned RAID for my root |
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filesystems paid off, as I was able to learn, create, and test the |
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individual components to that point, before I even /began/ worrying about |
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how LVM2 fit into all of this. |
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|
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Since I knew I had a basically working RAID system by then, not only was I |
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able to learn and test LVM2 as an entirely separate from the actual |
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boot kernel and the RAID component, but I was under MUCH less stress while |
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doing so, since even if LVM2 didn't work at that point, I knew I could |
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simply fall back to the old partitioning methods I knew so well, and that |
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it couldn't be an issue keeping me from completing setup of a working |
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system. Under those conditions, I reviewed the LVM2 HOWTO I had studied |
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earlier in ordered to figure out how to actually design the thing I had in |
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mind, this time actually doing the physical setup in practice. Again, by |
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this time it was surprisingly easy, as it was just one more layer added to |
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a system I already knew was working, and the HOWTO and Gentoo |
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documentation, both at the Gentoo site and in the sample config file as |
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merged, was actually quite good and very clear. |
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|
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So... if you are having problems, contrasting your approach with mine, I'd |
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have a couple suggestions. (1) Get the EVMS layer out of the way until |
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you actually get the LVM2 layer beneath it working, groking the LVM2 layer |
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better as you go as an added benefit. (2) Even if it's temporary, just |
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to familiarize yourself with how things actually work, consider breaking |
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down the components as I did, separating the RAID from the LVM2, and |
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learning one at a time. Once you know your RAID is working and are |
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at least working comfortable with mdadm or raidtools, /then/ add in the |
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LVM2 layer. Once you are comfortable working with it as a component at |
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that level, either add in the initramfs aspect or the EVMS aspect, but not |
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both at once, and get comfortable working with it. Then and only then, |
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throw in the other, completing the system the way you originally intended. |
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|
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It may also help to get familiar with initramfs on its own, quite apart |
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from the whole RAID/LVM2/EVMS thing. However you are running now, try it |
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there and figure out how the whole initramfs thing works at least to the |
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level you can be fairly confident of tracking down the problem to it if |
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that's where it is, before you worry about the other stuff. That way, you |
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can throw that knowledge you already have into the RAID/LVM2/EVMS mix at |
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the proper time. Of course, if you do this, you'll have already gone |
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where I've not yet tread, since I do NOT have that practical level of |
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knowledge of how initramfs actually works, altho I've read enough to know |
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a bit of the theory. |
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|
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-- |
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Duncan - List replies preferred. No HTML msgs. |
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"Every nonfree program has a lord, a master -- |
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and if you use the program, he is your master." Richard Stallman |
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|
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-- |
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