Linked by Thom Holwerda on Tue 10th Mar 2009 15:05 UTC, submitted by vijayd81
Linux In Linux distros, how do you know how much space to assign for each partition? And what if you do this and then later run out of room? Well you could delete data or move it off to other partitions, but there is a much more powerful and flexible way. It's called Logical Volume Management. LVM is a way to dynamically create, delete, re-size and expand partitions on your computer. It's not just for servers, it's great for desktops too! How does it work? Instead of your partition information residing on your partition table, LVM writes its own information separately and keeps track of where partitions are, what devices are a part of them and how big they are.
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Member since:

The way I understand it, the fact that LVM doesn't honour write barriers doesn't have any bearing on performance. However, it does mean that journalling filesystems aren't 100% protected from corruption after power cuts.

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ephemient Member since:

My recollection was wrong -- it seems that when barriers are turned off, Linux filesystems act unsafely instead of simulating barriers with flushes and waits. So the lack of barriers actually improves performance.

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giddie Member since:

Turning barriers off at the filesystem level will certainly improve performance. However, if barriers are enabled for a filesystem on an LVM device, you'll get the overhead of using barriers in the filesystem code (I believe), but those barriers won't be honoured by LVM.

If this is the case, when using LVM it makes sense to disable barriers on the filesystems in question, as they're not horoured and will decrease performance.

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