Mailinglist Archive: opensuse (1125 mails)

[Carl Hartung <opensuse@xxxxxxxxxxxxx>]

On Sun, 06 May 2012 22:00:59 -0400
Anton Aylward <opensuse@xxxxxxxxxxxxxxxx> wrote:

> John Andersen said the following on 05/06/2012 09:31 PM:
>
> > As for mixing and matching size with LVM, its almost always an
> > accident waiting to happen. When your partition is scattered across
> > multiple drives, a failure of any one will likely take down
> > everything.
>
> Yes, you *CAN* configure LVM that way.
> it is one of the *MANY* ways you can configure LVM and because of that
> it is a reason many people find LVM confusing and difficult to use.
> It is fraught with decision alternatives you have to make.
>
> That being said those alternative also allow you to do things like
> mirroring, yes *REAL* mirroring.  And you have the flexibility of
> doing it on a file system basis, not just a drive basis.
>
> Yes, you can also stripe across spindles and scatter-gather across
> spindles with LVM and yes that will cause a catastrophe if you loose a
> spindle.  But no-one is forcing you to use that rather than mirroring.
>
> The same applies with RAID.  There are many ways of doing it and not
> all offer reliability in the event of a loss of a spindle.
>
> The OP mentioned the need to protect the data but no the OS.
> using different strategies for different file systems is a capability
> of LVM not enjoyed by RAID.
>
>
> > LVM was not made for reliability, it was made to allow building
> > big volumes from several smaller devices.
>
> That too.  LVM has many capabilities.
> Don't focus on just one.
>
> Hmm. Some configurations of RAID can be said to allow building big
> volumes by spreading a file system across several small devices as
> well.
>
> It all depends on how to choose to configure things, doesn't it?
>
> > Its really not the right tool for the job, even if it can be
> > forced into that task.
>
> I wouldn't call it 'forcing' any more than choosing a particular RAID
> is 'forcing'.
>
>
> > http://serverfault.com/questions/279571/lvm-dangers-and-caveats
>
> Some of that is so wrong as misleading that its not worth discussing.
>
> That you can screw-up something though ignorance and inexperience
> applies just as much to RAID as LVM ... or anything else for that
> matter -- there are many examples of that in the software world!

Anton, I'd recommend you actually study the lengthy thread at John's
link. Overall, the comments there are quite positive about LVM2 in
spite of some specific caveats (see 'pvmove data loss', in
particular, plus a decidedly steep(er) learning curve, even for admins.)

I really enjoy frank discussions addressing pros and cons from
people like you two -- each with lots of contemporary hands-on
experience -- and, imho, the thread John referred us to falls into that
category.

regards,

Carl
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