On Sep 19, 11:35am, buh...@nfbcal.org (Brian Buhrow) wrote: -- Subject: Re: high load, no bottleneck
| Hello. the worst case scenario is when a raid set is running in | degraded mode. Greg sent me some notes on how to calculate the memory | utilization in this instance. I'll go dig them out and send them along in | a bit. In theory, if all your raid sets are in degraded mode at once, and | i/o is busy, you could be highly impacted, since you can have up to 40 | i/o's outstanding for each raid set with my configuration option. However, | even on machines with multiple raid5 sets, with 2 of them running in | degraded mode, I've not seen a memory bottleneck. I don't recommend this, | of course, but somethimes stuff happens. In any case, except for the | potential memory utilization, there's no down side to setting this number | in the kernel and not worrying about it anymore. In fact, this is what I | do for all our machines around here regardless of whether the machine is | hosting raid1 sets, raid5 sets or a combination of the two. If we are going to add a sysctl, we might also put a different value for the raid-degraded condition? Ideally I prefer if things autotuned, but that is much more difficult. christos