y need is more physmem. Don’t >> provision any swap at all. This isn’t 1985. > > Well. Why keep lot of boot-time-only code sitting in RAM instead > of having it gradually paged out? > > https://chrisdown.name/2018/01/02/in-defence-of-swap.html
Note that this is from 2018. I'm skeptical that the amount of boot-time-only usage is nontrivial. Swap also confounds expanding filesystems on the boot device, which many people under provision and/or over partition. >"swap should be double your physical memory size ><https://superuser.com/a/111510/98210>" That smells like an idea from the days of BSD-style swap, where swap backed rather than extended physmem. > _Some_ swap space is a nice bonus. Of course, when it gets used > for page-ins as well as page-outs during regular use, more RAM > is needed instead. Exactly. > >>> Then I created a partition covering the rest of the free space on >> each NVMe >>> and used both of them as physical volumes for a single LVM volume >> group: >> >> Sharing the boot volume with data is not an ideal strategy. I have >> a customer who got themselves into an outage doing that. You have a >> zillion SAS/SATA slots empty, put a pair of SSDs into each system for >> boot/OS, mirror them with MD, and don’t use them for data. > > For my workload, the bottleneck (if any) are the HDDs, so NVMes have lots > of idle time, even with some WAL and OMAP traffic hitting them. Note that instate %util has little meaning on any OSD. And there's more to the equation than "idle time". > On one of my clusters, the nodes are used both as Ceph OSDs _and_ > as KVM hosts running many instances (with volumes on Ceph RBD > on the very same cluster). No problem with that. Converged architecture, Proxmox-style. Nothing wrong with that if there are sufficient resources and osd_memory_target is managed appropriately. > Even small servers these days have insane amounts of CPU power > (especially relative to what is needed for HDD-based RGW traffic), > so why keep them idle and consuming electricity most of the time? That's a common assertion, and in some cases it's quite valid. It does mean, however, that compute and storage have to scale together. _______________________________________________ ceph-users mailing list -- [email protected] To unsubscribe send an email to [email protected]
