[rabbitmq-discuss] RabbitMQ writes non stop to disk

Thu Oct 27 02:29:55 BST 2011

Raphael,

On 27/10/11 01:47, Matthias Radestock wrote:
> Can you find out what files the 6k/s writes are going to? It can't be
> just the persistent message store since, as you observed, that's only
> writing 16M about every couple of minutes. And while I would expect to
> see some writes to the queue index journal files, these shouldn't add up
> to anywhere near 6k/s with the traffic levels you are reporting.

Btw, are you definitely looking at the correct column in the iostat output?

As a test I ran 'MulticastMain -f persistent -q 1 -r 17 -s 50000' (i.e. 
17msg/s, persistent, qos=1, 50k message size), and the same with "-r 8" 
- which roughly corresponds to the rates I saw reported on the two 
queues in the system with non-negligible traffic. I adjusted rabbit's 
memory thresholds s.t. the target_ram_count of the queues dropped to 
zero but w/o raising the memory alarm. 'iostat -d -x 10' shows:

Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s 
avgrq-sz avgqu-sz   await  svctm  %util
sda               0.00   219.70    0.00   57.70     0.00  2219.20 
38.46     0.61   10.57  10.55  60.90

So that's just 57.70 writes/s.

Matthias.