Adding physical volumes to LVM partitions - what happens to existing files? And general SSD optimization

Question

I've got two drives in my laptop, a 120GB SSD and a 320GB hard drive. Ubuntu (11.04 amd64) is on the hard drive, set up using LVM. Now, I got this SSD recently, and I want to put Ubuntu on it for faster boot times and such. What exactly happens if, say, I create a new physical volume on the SSD, and add new physical extents to my existing logical volumes (say, / and /home)? Will files be moved over to the SSD at all? Is there striping that goes on? The goal is for my sytem to be faster, so I want to make sure that important files are on the SSD but it would be nice if I could avoid reinstalling completely. I'm still not that comfortable with LVM. I actually tried doing a fresh install to my SSD but for some reason it failed in the middle of installing software packages (after I set up the new physical volume and stuff for the SSD).

In general, how do people run Ubuntu on systems with a hard drive and an SSD, for best preformance? Thanks!

Edit: I should mention that 80GB of the SSD is allocated to Windows (for games) so Ubuntu only has about 35GB (random system reserved things and mistruths in advertising make up the last bit).

Answer 1

What exactly happens if, say, I create a new physical volume on the SSD, and add new physical extents to my existing logical volumes (say, / and /home)? Will files be moved over to the SSD at all?

No

Is there striping that goes on?

No. Unless you create a new 'stripped' LV. see here

In general, how do people run Ubuntu on systems with a hard drive and an SSD, for best preformance? Thanks!

I don't know, but since you have a large SSD, I guess you have three options:

1. Put most everything on the SSD. Use HDD for backups, data not used very frequently and swap space maybe. (This could bring significant speed and battery saving because the HDD will hardly be used.)
2. Create a 120GB Mirroring RAID from SSD and HDD to use with LVM for most everything. Remaining space on HDD for extra data. (Speeds up reading, not writing.)
3. Create a 120GB Stripping RAID from SSD and HDD to use with LVM for most everything or used a sripped LV. (Should speed up reading and writing significantly, but actual performance is hard to predict due to the different characteristics of HDD and SSD perfomance.)