On Fri, Jun 20, 2003 at 04:29:54PM +0100, Geoff Dolman wrote: > On Fri, 2003-06-20 at 12:02, Heinz J . Mauelshagen wrote: > > On Fri, Jun 20, 2003 at 10:50:32AM +0100, Geoff Dolman wrote: > > > Hi > > > > > > I am soon to take delivery of a new Server: It's configuration is to be > > > > > > 584GB disk (hardware raid5) 4 cpu (with Intel hyperthreading) > > > > > > 32 GB RAM > > > > > > > > > I intend to use RH Advanced Server 2.1 (whatever the latest kernel is at > > > time of install). > > > > > > I would ideally like to be able to snapshot dump this machine (the > > > largest partition will use most of the available disk space (4-500GB)). > > > > > > Is there any caveat or issue that I should be aware of with lvm in this > > > configuration? > > > > Snapshots trigger a virtual memory problem with highmem enabled in kernel 2.4 :( > > > > The snapshot exception tables hold in RAM can grow quite big in case > > of large snapshot sizes (which you might not need in case your filesystem(s) > > are not heavily updated during the lifetime of the snapshot). > > > > Hi Heinz > > What do you recommend I do? Because of the highmem problems which are not fixed in 2.4.21 TTBOMK (and I am afraid they wonÄt be before 2.6), you can run snapshots without highmem enabled only, which for obvious reasons can't be an option you prefer ;) > What is (if any) the largest filesystem I > can snapshot in this set-up? Depends on your memory load and fs update ratio during a snapshots lifetime. With 1GB of RAM used only, that would be up to ~512GB snapshot size (roughly calculated) presuming you could use have of your RAM for the memory resident snapshot excpetion table and go with 32k snapshot chunk size. The ~512GB are the upper limit of changes to the original LV (which is a lot). As a rule of thumb, you can calculate with ~5% changes to your original LV, which means you'ld need a ~100GB snapshot for a 2TB original LV. > > -- > Geoff Dolman <geoff.dolman@cimr.cam.ac.uk> > > _______________________________________________ > linux-lvm mailing list > linux-lvm@sistina.com > http://lists.sistina.com/mailman/listinfo/linux-lvm > read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/ -- Regards, Heinz -- The LVM Guy -- *** Software bugs are stupid. Nevertheless it needs not so stupid people to solve them *** =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- Heinz Mauelshagen Sistina Software Inc. Senior Consultant/Developer Am Sonnenhang 11 56242 Marienrachdorf Germany Mauelshagen@Sistina.com +49 2626 141200 FAX 924446 =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=- _______________________________________________ linux-lvm mailing list linux-lvm@sistina.com http://lists.sistina.com/mailman/listinfo/linux-lvm read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
