> > > > > In regards to setting read ahead, how is this set for nvme drives? Also, > below is our compression settings for the table… It’s the same as our tests > that we are doing against SAS SSDs so I don’t think the compression > settings would be the issue… > > >
Check blockdev --report between the old and the new servers to see if there is a difference. Are there other deltas in the disk layouts between the old and new servers (ie. LVM, mdadm, etc.)? You can control read ahead via 'blockdev --setra' or via poking the kernel: /sys/block/[YOUR DRIVE]/queue/read_ahead_kb In both cases, changes are instantaneous so you can do it on a canary and monitor for effect. Also, i'd be curious to know (since you have this benchmark setup) if you got the degradation you are currently seeing if you set concurrent_reads and concurrent_writes back to their defaults. -- ----------------- Nate McCall Wellington, NZ @zznate CTO Apache Cassandra Consulting http://www.thelastpickle.com
