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Re: Linux domU disk questions

On Sun,  2 Jan 2011 09:18:19 +0100
"Niels Dettenbach" <> wrote:

> > is LVM backed DomU as fast as DomU on physical disk?
> LVM is typicaly faster then a file based disk image in XEN backend.
> Comparing phys and lvm is not a xen related question as this is not
> part of xen / there is no real difference in how XEN handles it (both
> handled by the phys: driver).
> As afaik lvm backends are the widest spreaden in productive XEN usage
> and even typical in enterprise products i would assume that it is the
> most tested constellation.
> Comparing LVM and physical performance of NetBSD is a thing byself
> and there is no general answer in practice as it depends from a wide
> range of factors i.e. underlying hardware (I/O-sys /
> RAID-controller), the LVM-configuration, the "overlying" fs and - not
> at least - your applications above.
> There are a lot of discussions around this topic in the net.
> Even if LVM could be thought as an additional "layer" between
> filesystem and hardware most practical experiments or tests shown no
> or a minimal only performance impact of LVM compared to a "straight"
> hard disk.
> In case you run a high level storage system LVM might be not a help
> in your situation anymore - so it might be that the possibly but
> minimal impact of LVM weights harder then a null weighted comfort of
> LVM in your situation.
> For reasons of comfortability LVM often should be the first choice -
> especially (but not only) in the server area.

Thank you for your detailed reply Niels. I was in two minds about LVM
but you have persuaded me! However, it appears it's not in 5.1 so I
will wait until 6.0 comes out. I am too new with NetBSD to try -current.


Gerard Lally

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