On Saturday 10 June 2006 01:30pm, Nicolas Mailhot wrote: > Le samedi 10 juin 2006 à 11:08 -0600, Lamont R. Peterson a écrit : > > Swap works best when you don't have extra layers of abstraction and when > > the swap device is contiguous storage. I know; LVM only adds a tiny bit > > of overhead, but when you start hammering on swap, every last ounce > > helps. > > When you have multi-disk systems an LVM swap can be faster than a > separate swap, it only has to extend through several disks. And even the > rest of the time, the ease of administration LVM brings justifies swap > LVM nowadays IMHO. Dedicated swap partitions are pretty much a PITA when > the hardware (disks) changes - either you systematically add a swap > partition to every single disk, or you pray the one your swap is on will > never be pulled from the box. I don't see where the benefits of LVM enhance the use of swap, other than the example you gave of spanning multiple disks. But, you can get that benefit by creating swap partitions of the same priority (depending on the speed variations in your disks, of course) and allowing the swap code to use them all. IIRC (someone feel free to correct me on this if I'm wrong), the kernel swap code will distribute swapped pages amongst all available swap devices at the same priority level, when that level is the one it's currently working with. Simply put, LVM doesn't bring any benefit to the use of swap, because we don't care what's on swap (other than, perhaps, for security reasons, that is). Besides suspend-to-disk/hibernate software that uses a swap partition to get the job done, any data stored on swap is completely abandoned from session to session. Let's say I'm upgrading my system to a new disk. LVMs pvmove is great and takes care of anything on LVM. If swap is separate, then I simply have to run this series of commands: # fdisk /dev/sdb # assuming the new disk is /dev/sdb, create the swap partition and the rest of the disk can be LVM # mkswap /dev/sdb2 # assuming /dev/sdb2 is the new swap partition # swapon /dev/sdb2 # swapoff /dev/sda2 # assuming that /dev/sda2 is the old swap partition; you reall don't *have* to do this step At this point, the system is using the new swap device. I don't see why you would say that a swap partition is a PITA. The only other thing you might need to do is to edit /etc/fstab and change the entry for the old swap to the new one. What if I decide later on that my one swap partition isn't big enough? I'll create a swap file or a swap LV (probably making it a lower swap priority) and use that until I upgrade the hard drive again. Easy. What it I find myself having to regularly increase (or otherwise alter) the size of my swap device(s)? Well, then I've got bigger problems, probably, and should most likely be looking at more RAM rather than or in conjunction with reorganizing swap. Or perhaps, I should be adding a dedicated swap disk. -- Lamont R. Peterson <lamont@xxxxxxxxxxxx> Senior Instructor Guru Labs, L.C. [ http://www.GuruLabs.com/ ] GPG Key fingerprint: F98C E31A 5C4C 834A BCAB 8CB3 F980 6C97 DC0D D409
Attachment:
pgpiRgyGmn8nz.pgp
Description: PGP signature
-- fedora-devel-list mailing list fedora-devel-list@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/fedora-devel-list
