Slow disk drain and create rate


Hello everyone,

I’m currently testing out couchbase enterprise edition using a single node on my local machine running ubuntu 12.04LTS.

The machine specs are:
I7 8core
750GB ATA WDC Harddrive

The cluster quota is 8gb and I have one bucket ‘users’ with 4gb assigned to it. My document sizes are on average 250bytes, I have a java application deployed onto tomcat on the same machine, when I do any number of inserts the writes to disk never exceed 100 and average 60. For example the disk write queue will be 25k and a drain rate of 60 to 100.

I have the standard disk write concurrency of 3. Any ideas or info about my problem would be greatly appreciated!





Even if this does not look like good numbers, I would like you to analyze more data, maybe it is the max that your hardware can do.

One thing you can do is to look at iostat to see what the utilization of the disk is. If it’s being heavily used, then that’s probably just as fast as it can go. If this is not used,…, we need to continue the investigation.

I would recommend first increasing the incoming writes to confirm that batching is a strong culprit. And then increasing the workers to 6 should double that rate. I wouldn’t recommend going to 8 on this system since he’s only got 8 cores and should leave ~4 of them for erlang/memcached/etc.