>I also strongly second the comments made about VM vs large quantities of >IOPs. We're debating virtualization of servers here (umich) and the jury >is still out. Thomas Kula has more to say on that topic in his note, but >in general I have strong doubts about any file server that runs in >anything except a one-server-per-phyisical-host model.
I'd modify that comment to include the words "on Intel hardware." Largely, we're discussing the defects in current Intel virtualization. I would have zero hesitation to deploy file servers on virtual machines on Power or s390x virtual machines -- this is really a case of right tool, right job; not all virtualization solutions are created equal. A suggestion: Even on Intel, if you do go VM-based, start at half the RAM size as on physical hardware and measure performance, then increase the size of the VM by 32M and retest until you reach a steady-state with 1-2% swapping inside the VM at a maximum. Unless your OS supports controlling the size of the disk cache, as the working set of the guest OS increases and more of the guest RAM is consumed with I/O buffer cache, it becomes harder to schedule the guest, which hurts the performance of the guest. Often a 256M guest outperforms a 2G guest in a VM environment -- it's less difficult to schedule a 256M guest than bigger guests. _______________________________________________ OpenAFS-info mailing list [email protected] https://lists.openafs.org/mailman/listinfo/openafs-info
