On 2022-07-06 2:59 PM, Shawn Heisey wrote:
If the mounted filesystem is one that the OS can cache, and there is enough spare memory, then a lot of the mmap requests that Lucene makes won't ever hit the actual disk. Most block devices can be cached. I would expect that to be the case for iSCSI, because it should be a block device from the OS perspective. I think most network filesystems (NFS, SMB, etc) cannot be locally cached. They are probably cached on the server side, but then you'd be limited by network bandwidth and latency. The transfer rate of most 7200RPM SATA disks is a little bit faster than gigabit ethernet.
This way lieth dark magick and madness, of course, but I'm curious what the optimal config would be for a container infra. For bare metal a large PCIe SSD should be the best bang for the buck, but on kube the "disk" is probably iSCSI volumes and you may not have much control over any OS buffering that may exist. Or not.
Dima
