Matthias> At $work we've been having a discussion about what the right Matthias> amount of swap is for a given amount of RAM in our standard Matthias> linux image and I'm looking for additional input.
Oh goody, fun topics on Friday! Matthias> The "old school" conventional wisdom says "swap = 2x RAM". Matthias> The more modern conventional wisdom seems to vary from "swap Matthias> = 1x RAM + 4G" to "swap = 4G regardless of RAM". Matthias> So if you're running/managing a Linux HPC cluster, or you Matthias> have strong opinions on the subject, or you just want to Matthias> comment :), I love to hear you're thoughts. Matthias> Some info about our environment... We have several HPC Matthias> clusters scattered around the globe with anywhere from 100 Matthias> to somewhat over 1000 systems in each cluster. Workload in Matthias> the clusters is managed using LSF and typically they are Matthias> configured to have one job-slot per cpu. The memory configs Matthias> in each system ranges from 4G RAM up to 512G. Not sure if Matthias> the OS version matters but in case it does, we're primarily Matthias> running RHEL4u5 and starting a migration to RHEL5u3. We're running something similiar, though smaller, 20-30 systems upto 120 or so in our biggest center. We migrated from LSF to NC (http://www.rtda.com) and it's been fairly painless. Some issues, but nothing we haven't worked around. On our systems, we tend to make a big swap partition and then mount /tmp on top of it. So we use swap (and VM) to cache /tmp usage as needed. We've got mostly dual CPU Opterons with 16Gb RAM, plus more dual/quad core, dual and quad CPU systems with 32 to 256Gb of RAM. Mostly Opterons, but the newer stuff is all Xeons. I agree with all the comments which state if you swap, your dead. No arguement there. But what about when you have a small or medium memory job which writes a bunch of /tmp files? Do people have /tmp local, or do they write over the network via NFS? John _______________________________________________ Tech mailing list [email protected] http://lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
