I decided that the next time I reformatted my main desktop computer (this one) I would have a ssd installed in it to use for the boot drive. Now that Centos 7 is on the horizon, I'm thinking that the time is approaching when I'll want to do that.
The last time I set up a computer with a ssd in it, that was the only drive that it had. I changed issue_discards=0 to issue_discards=1 into the /etc/lvm/lvm.conf file, set up cron to run fstrim on that drive on a weekly basis, and that was it.
Since this next setup will have both a ssd and a regular hard drive in it, is there some way that I should specify that issue_discards=1 applies only to the ssd or does that matter? I see that the explanation in the lvm.conf file says "If set to 1, discards will only be issued if both the storage and kernel provide support." so I'm left with the impression that the issue_discards setting won't affect a regular hard drive even if it is set to 1.