On 23/07/11 00:09, Ragheb Rustom wrote:
Dear Markus and Amos,

I have done the changes you have proposed. I have dropped the max-size on COSS 
partition to 100KB so the COSS cache_dir line now reads as follows:

cache_dir coss /cache3/coss1 110000 max-size=102400 max-stripe-waste=32768 
block-size=8192 membufs=100
cache_dir aufs /cache1 115000 16 256 min-size=102401
cache_dir aufs /cache2 115000 16 256 min-size=102401
cache_dir aufs /cache4/cache1 240000 16 256 min-size=102401

After doing this I have noticed the following warnings every now and then 
(usually every 1 - 2 hours) in the cache.log file

squidaio_queue_request: WARNING - Queue congestion

What I also noticed using iostat is that the big HDD with AUFS dir is handling 
a lot of write requests while the other 2 HDDS with AUFS dirs rarely have disk 
writes. Is this normal behavior since I have 3 AUFS cache_dir shouldn't squid 
disk read and write access be somewhat equal between the 3 AUFS partitions? Do 
you think I should go for a higher max-size on the COSS partition to relieve 
the extra IO from the big AUFS cache_dir?


The default selection picks the directory with most available space. So for the first 130GB of unique cacheable objects that would be cache4.
 http://www.squid-cache.org/Doc/config/store_dir_select_algorithm/

You can set that to "round-robin" to level the writes more evenly over the AUFS disks. Wont be perfectly even balancing due to differences in object size an a few other factors.

"Queue congestion" is likely a result of everything big going to cache4 initially.
  http://wiki.squid-cache.org/KnowledgeBase/QueueCongestion

Amos
--
Please be using
  Current Stable Squid 2.7.STABLE9 or 3.1.14
  Beta testers wanted for 3.2.0.9

Reply via email to