LVM - Any benefit of Not Using the Whole Partition?

[dman777]

I have 100gig SSD drive that I am going to use for KVM guests. At first I was going to just make one large partition for a VG and make each logical volume a KVM guest. I probably will plan on using 50% of it initially. But then I read where I should not partition all the drive and only partition what I need for LVM. Is there any real benefit to making separate partitions of the SSD drive if I am eventually going to add them to the same Volume group anyways?

[srs5694]

AFAIK, no. IMHO, the benefit to creating a smaller LVM partition (physical volume) that's only as big as you need it to be is that you can then use the unpartitioned space for something else if you decide to do so. For instance, you could install another OS entirely in that space, for a dual-boot setup. If you're 100% certain that you'll never want to do this, there's little point to creating a smaller partition (which in turn means you'd need two or more physical volumes when you get around to using the space in the LVM).

[depontius]

Please check me if I'm wrong on this...

There might actually be some good in using LVM to make sure that the entire disk isn't available for use. That gives the SSD control firmware more fodder to play with when remapping sectors to level wear.

This is dependent on the assumption that SSD firmware will take a region that has been historically read-mostly/only and swap it with a region that has been historically heavily written. I don't know that this actually happens, but I get the impression that it does.
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.sigs waste space and bandwidth

[dman777]

You are correct...this is for garbage collection. I already over provisioned and left 20 gigs of raw space for it. But as far as LVM goes, I was wondering if there is any benefit. Could the partition become messed up and having the extra partition be a benefit? I never really seen a partition get messed up before though. Would the LVM work quicker on two partitions of the same block device rather than one large partition of the same block device?

[depontius]

I actually don't like LVM after having used it,and have mostly removed it from use. It adds another level of indirection into your data storage, potentially making it harder to pick up the pieces after a problem. For what I would expect/wish out of LVM, fiddling with partition size and placement, I've been able to get that out of booting a gParted disk.

That said, I have 2 systems now (neither Gentoo) that use LVM as an encrypted container. It's the "standard deployment", so I'm using it. But in this case LVM does simplify life.

I believe the performance penalty for LVM is negligible, but neither do I envision it improving performance, either. IMHO it's pretty much for convenience.
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.sigs waste space and bandwidth

[srs5694]