Re: LVM info - OTHER than HOWTO's
On Wed, Nov 18, 2015 at 10:02 PM, Richard Owlett <rowlett@cloud85.net> wrote:
> On 11/18/2015 4:07 AM, Joel Rees wrote:
>>
>> 2015/11/18 9:09 "Richard Owlett":
>>>
>>>
>>> In some of my reading I came across a page recommending LVM for ease
>>> of adjusting space.
>>
>>
>> Yeah. I'm not using it now, but it did come in handy when I was
>> still getting a feeling for partitioning.
>
>
> I've a machine set aside for experimenting with how an install is configured
> for a couple of personal projects. Relative space usage cannot be determined
> in advance.
Sounds like an excellent reason to at least experiment with LVM.
One reason I used it in the past was that, for some reason, I did not
want to use the so-called DOS/BIOS (or linux) extended partitions and
I needed lots of partitions. LVM is a bit more flexible. (I don't
recall trying to use more than one linux extended partition, I've only
recognized that they seem to exist lately.)
With GPT the limits on numbers of partitions, etc., are supposedly
relaxed, but I haven't done that, yet.
>>> When searching for more information all I'm finding are essentially
>>> HOWTO's
>>> with only a couple of paragraphs on "Whats" and "Whys".
>
> Essentially nothing
Uhm, no news is good news?
>>>
>>> on "Why not".
>>>
>>
>> Reasons not to use it range from laziness to not needing it after
>> all (right now) to wanting to use incompatible software. My
>> impression is that the incompatible software usually tells you
>> somewhere it's not compatible.
>
>
> I have a current possible use but want to know in advance of rough spots to
> estimate if the effort is likely to be productive.
Rough spots?
I never saw any in over ten years of use. That's part of the reason
you don't hear much about it.
Well, the GUI gadget is a bit slow, slower than gparted when
re-scanning your disk after an edit is applied. But that's only a
problem when you are in a rush, but you really don't want to be in
that kind of a rush when messing with your partitions.
LVM is much more flexible and less prone to do things to your data
than, say, the tools that re-size your partitions the hard way. You do
still have to exercise common sense, however.
I've lost a re-sized partition permanently using a commercial tool
whose name I refuse to remember.
I lost a bunch of LVM partitions once through pure carelessness and
used the LVM maintenance tools to recover them. Took a couple of hours
to read the manuals, recover, and be on my way. Kept using that
partition map for several years with no problems.
>>> No information on dual boot.
>>
>> That's fairly straightforward.
I think I have heard of people booting straight out of LVM partitions,
but that takes more gum tape than I like to use. I do believe grub is
able to look into LVM partitions somewhat these days, so you may want
to play with having grub on a ("BIOS/DOS" map) primary partition
booting to a boot/root partition in an LVM managed logical volume.
>>> Suggestions?
>>
>> man -k lvm ?
>
> That lead to a productive but OT rabbit trail ;)
> Man pages are by design inherently very detailed HOWTO's.
>
No, those are not rabbit trails. That's basically the stuff you need
to know when you are considering using it.
If you are worried about it, use your experimenting box first. If not,
I'm not sure why you would think twice unless your RAID docs say they
don't play nice with LVM (or LVM doesn't play nice with them) or, say,
you are using that XML file system or some other exotic file system.
your usual efs2, 3, and 4 all work fine in LVM partitions. After
adding extents to a logical partition, you may need to add inodes, and
you do want to be careful when shrinking a partitition with live data
in it. (Common sense, right? Back-up the data, etc.)
Oh, use the GUI at first. It helps you visualize what you are doing.
Other than being slow, it works well for initial partitioning, adding
extents, and reminding yourself where the spare physical partitions
are, etc.
--
Joel Rees
Be careful when you look at conspiracy.
Arm yourself with knowledge of yourself, as well:
http://reiisi.blogspot.jp/2011/10/conspiracy-theories.html
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