On 10/6/22 01:57, Dominique Bejean wrote:
One of our customer have huge servers- Bar-metal - 64 CPU - 512 Gb RAM - 6x2Tb disk in RAID 6 (so 2Tb disk space available) I think the best way to optimize resources usage of these servers is to install several Solr instances.
That is not what I would do.
Do not configure disks in RAID 6 but, leave 6 standard volumes (more space disk, more I/O available) Install 3 or 6 solr instances each one using 1 ou 2 disk volumes
RAID10 will get you the best performance. Six 2TB drives in RAID10 has 6TB of total space. The ONLY disadvantage that RAID10 has is that you pay for twice the usable storage. Disks are relatively cheap, though hard to get in quantity these days. I would recommend going with the largest stripe size your hardware can support. 1MB is typically where that maxes out.
Any use of RAID5 or RAID6 has two major issues: 1) A serious performance problem that also affects reads if there are ANY writes happening. 2) If a disk fails, performance across the board is terrible. When the bad disk is replaced, performance is REALLY terrible as long as a rebuild is happening, and I have seen a RAID5/6 rebuild take 24 to 48 hours with 2TB disks on a busy array. It would take even longer with larger disks.
What I am not sure is how MMapDirectory will work with several Solr instances. Will off heap memory correctly managed and shared between several Solr instances ?
With symlinks or multiple mount points in the solr home, you can have a single instance handle indexes on multiple storage devices. One instance has less overhead, particularly in memory, than multiple instances. Off heap memory for the disk cache should function as expected with multiple instances or one instances.
Thanks, Shawn
