Gentoo Archives: gentoo-desktop

From: Duncan <1i5t5.duncan@×××.net>
To: gentoo-desktop@l.g.o
Subject: [gentoo-desktop] Re: disk partitioning
Date: Wed, 07 Feb 2007 10:44:17
Message-Id: eqc9vp$it1$3@sea.gmane.org
In Reply to: Re: [gentoo-desktop] Re: disk partitioning by Kevin Hanson
1 Kevin Hanson <tuxpert@×××××××.net> posted 45C92BFC.2020503@×××××××.net,
2 excerpted below, on Tue, 06 Feb 2007 19:31:40 -0600:
3
4 >> Did you look in to EVMS at all. I am setting up a similar system to
5 >> yours...4 stat disk, linux raid, etc. However, I really wanted to use
6 >> EVMS and am only partially successful. I have, as of now, been able
7 >> to get the EVMS stuff correctly in initrd such that I can complete a
8 >> boot.
9 >>
10 >> Just curious if you'd looked into EVMS at all and if you had any
11 >> thoughts.
12
13 > Wow...I didn't type well in the above message...it's supposed to be
14 > 'sata' not 'stat' disk...
15 > And I was trying to say "I have, as of now, NOT been able...."
16
17 It seems to be going around. =8^(
18
19 [I'm adding this after typing the below. It occurs to me I might be
20 discussing everything /except/ what you need. If so, I'm sorry. I'm
21 posting this however, in case it can do /someone/ some good, even if
22 that's not you. Hopefully it helps you too, but if not, after putting all
23 this effort into it, I hope it helps /someone/. =8^) ]
24
25 I haven't looked into EVMS, no. However, as I understand it, while EVMS
26 and LVM2 were at one time built on different kernel mechanisms, when LVM2
27 was selected for merging into the mainline kernel (2.5 era I believe,
28 2002), EVMS decided rather than fight it, to take their already great
29 management tools and make them work with the LVM2 framework as it was
30 merged into the kernel. =8^) Thus, I believe EVMS is now simply what
31 amounts to a GUI front-end to the LVM2 system as it exists in the kernel
32 and lower level command-line tools.
33
34 If it's not working for you, presumably the issue is that something isn't
35 configured right in the lower level LVM2 layer. Sometimes you just gotta
36 dive in and get your hands dirty at the command line level to most
37 efficiently figure out what's going wrong, and this would appear to be one
38 of those times. You may or may not eventually figure out the issue at the
39 higher level, but once you understand what's going on at the lower level
40 and fix the problem, I'm guessing you should be able to go right back to
41 using your higher level interface for routine work, if so desired.
42
43 My approach was to take one thing at a time. First I studied RAID and
44 mdadm and got how it worked figured out at least enough to design the
45 system I wanted at that level. Then I did the same with LVM2. Honestly,
46 I was aware of the EVMS thing, but had forgotten the details, and it never
47 occurred to me to try it since I was under the impression that they had
48 lost out (they did with their lower layers, but just took their strengths,
49 the upper layers, and refitted them to the LVM2 framework, actually a
50 rather cool thing to do IMO) and were no longer a mainline Linux project
51 (I was wrong there, since they continued with their GUI front-end, just
52 built on LVM).
53
54 Actually, I had another thing to learn as well. When I started on Linux
55 using Mandrake, GRUB was far less mature and I learned LILO. When I
56 transferred to Gentoo, I just continued using LILO, for awhile just using
57 the Mandrake executable on Gentoo, even. Since I was setting up an
58 entirely new RAID system anyway, and already learning it and LVM2, I
59 decided it was time to bite the bullet and learn and switch to GRUB as
60 well, so I learned it too. =8^)
61
62 Then after I actually got an overview of how it all fit together, and had
63 designed my system at that level so I could actually start working with
64 it, I retraced the same steps only this time actually getting the
65 operational detail and putting it into practice as I went. Partitioned
66 RAID in particular, however, never /was/ entirely clear to me, until I
67 started actually doing it. That was mainly because it was new enough that
68 there were tantalizing mentions of it, but not the direct coverage of
69 every aspect of it, both theory and step-by-step, that I was able to get
70 with RAID and LVM2 in general, using mainly the three sources of each ones
71 HOWTO, together with the Gentoo LVM and RAID documentation.
72
73 Since I already knew I didn't want LVM2 on my root partitions, because
74 that would require the additional complexity of an initramfs and I wanted
75 to retain direct-kernel-boot, I was able to (1) do the physical drive
76 partitioning (no problem, I'd done that many times over the years), (2)
77 create and assemble the RAID-1 for /boot, (3) while still booting from my
78 separate single drive (legacy PATA), play with that until I got the
79 practical knowledge of how to actually get the kernel to see and assemble
80 the RAID, (4) while still booting from the separate disk, figure out how
81 to mkfs the assembled RAID-1, (5) still booting from the separate disk,
82 install the kernel and grub to the new RAID-1, (6) still booting the
83 separate disk, figure out how to get GRUB installed on the physical boot
84 sectors of ALL FOUR physical disks, (7) NOW figure out how to actually
85 boot grub from any of the four, and verify that it actually worked as I
86 intended, (8) get the GRUB config and kernel command line correct to
87 actually get from GRUB into a kernel installed on that RAID-1 /boot. (9)
88 NOW with the RAID-1 working and actually booting to the root on my
89 existing single drive, figure out the partitioned RAID-6 for the root
90 filesystems and LVM2 partition (this started to get easier since now I
91 only had to learn the difference between RAID-1 and RAID-6, and between
92 partitioned and non-partitioned RAID, I already had practical knowledge of
93 working with RAID in general using mdadm), (10) verify that there were
94 indeed no weird tricks to partitioned RAID I hadn't considered, and
95 actually partition the RAID-6 using cfdisk, (11) not yet quite believing
96 it could actually be this simple (but it was), since this hadn't been
97 covered so well in the documentation since partitioned RAID was so new,
98 mkfs the partitioned RAID-6 partitions, (12) mirror my existing root file
99 system off the legacy PATA drive onto the two RAID-6 root partitions, once
100 to each, working and backup, (13) figure out how to get GRUB to point the
101 kernel at these new partitions for its root, (14) actually boot into the
102 new partitions and see that everything so far was working.
103
104 Only at THAT point did I even START to consider the practical knowledge of
105 the LVM2 stuff. At that point, I had verified working partitioned RAID-6,
106 as I was booting into it as my root filesystem, so I knew at least to that
107 point, everything HAD to be working, since I'd not be able to boot into it
108 if not! Again, the lower complexity of the partitioned RAID for my root
109 filesystems paid off, as I was able to learn, create, and test the
110 individual components to that point, before I even /began/ worrying about
111 how LVM2 fit into all of this.
112
113 Since I knew I had a basically working RAID system by then, not only was I
114 able to learn and test LVM2 as an entirely separate from the actual
115 boot kernel and the RAID component, but I was under MUCH less stress while
116 doing so, since even if LVM2 didn't work at that point, I knew I could
117 simply fall back to the old partitioning methods I knew so well, and that
118 it couldn't be an issue keeping me from completing setup of a working
119 system. Under those conditions, I reviewed the LVM2 HOWTO I had studied
120 earlier in ordered to figure out how to actually design the thing I had in
121 mind, this time actually doing the physical setup in practice. Again, by
122 this time it was surprisingly easy, as it was just one more layer added to
123 a system I already knew was working, and the HOWTO and Gentoo
124 documentation, both at the Gentoo site and in the sample config file as
125 merged, was actually quite good and very clear.
126
127 So... if you are having problems, contrasting your approach with mine, I'd
128 have a couple suggestions. (1) Get the EVMS layer out of the way until
129 you actually get the LVM2 layer beneath it working, groking the LVM2 layer
130 better as you go as an added benefit. (2) Even if it's temporary, just
131 to familiarize yourself with how things actually work, consider breaking
132 down the components as I did, separating the RAID from the LVM2, and
133 learning one at a time. Once you know your RAID is working and are
134 at least working comfortable with mdadm or raidtools, /then/ add in the
135 LVM2 layer. Once you are comfortable working with it as a component at
136 that level, either add in the initramfs aspect or the EVMS aspect, but not
137 both at once, and get comfortable working with it. Then and only then,
138 throw in the other, completing the system the way you originally intended.
139
140 It may also help to get familiar with initramfs on its own, quite apart
141 from the whole RAID/LVM2/EVMS thing. However you are running now, try it
142 there and figure out how the whole initramfs thing works at least to the
143 level you can be fairly confident of tracking down the problem to it if
144 that's where it is, before you worry about the other stuff. That way, you
145 can throw that knowledge you already have into the RAID/LVM2/EVMS mix at
146 the proper time. Of course, if you do this, you'll have already gone
147 where I've not yet tread, since I do NOT have that practical level of
148 knowledge of how initramfs actually works, altho I've read enough to know
149 a bit of the theory.
150
151 --
152 Duncan - List replies preferred. No HTML msgs.
153 "Every nonfree program has a lord, a master --
154 and if you use the program, he is your master." Richard Stallman
155
156 --
157 gentoo-desktop@g.o mailing list

Replies

Subject Author
Re: [gentoo-desktop] Re: disk partitioning Lindsay Haisley <fmouse-gentoo@×××.com>