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I am setting up a small (1 user) email server. So far I have put in 2 x 1TB WD Red drives and set them up for LVM with RAID1 mirrored LVs.

I also picked up a 120GB Samsung 840 Evo but I can't figure out what to use it for.

I read that they recently added SSD caching to LVM in kernel mainline but I imagine it will be a year or two before that reaches Ubuntu.

What should I use it for then?

Should I get a second one for RAID so I can move the root (non-home) files to it for faster performance?

ljbade
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Well bcache is an option on 14.04.

dm-cache (for which lvmcache is apparently just a friendly frontend) seems faster according to benchmarks but seems quite painful to use directly. That should still be an option if you like, but it's a slog.

You could manually update (or find a PPA for) lvm2. This package is largely just a toolchain for exploiting Kernel features so (with a pinch of salt and many backups) should be relatively safe to run on 14.04.

Community
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Oli
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  • It looks like bcache is the one to use until lvmcache is available. Do you know if it is possible to delete the bcache superblock at a later date? – ljbade Aug 02 '14 at 01:32
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    I honestly don't know. With any of these modern approaches I would thoroughly suggest testing it before you throw any real-world data on it. That includes testing to see what happens to the RAID1 if the cache device dies. You can emulate most of these in a virtual machine fairly easily but also test on hardware. – Oli Aug 02 '14 at 13:01