AW: Re: Linux domU disk questions

["Niels Dettenbach" <nd%syndicat.com@localhost>]

> 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.

hth a little
cheers and good luck,

Niels.
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