On 08/09/2011 12:38 PM, Karri Vrkreddy wrote:
Hi,
We are using ATS as reverse proxy.
In our use case most of the data is dynamic ( responses from the backend hosts ) and need not be cached for more than 5-10 mins.
We currently configured it to have a disk cache size of 10 GB and we left
the proxy.config.cache.ram_cache.size as -1. So that would give us a ram cache
size of 10 MB.
Here are my questions :
1. Since the ram cache size is very small, does a TCP_HIT mean a disk
access ? ( this is a 16 GB node and lots of free memory, so I mostly buffer
cache plays a
I don't think we distinguish between RAM vs disk cache in the squid
logs, I'm not even sure it's possible to configure a log that does it
either. In fact, I think there was an RFE to add such log data.
However, you can certainly see how much RAM cache hit ratio vs disk
cache hit ratio you get, in the stats. That's not per request though.
10MB seems like an *incredibly* small RAM cache. Make it bigger ;).
significant role )
2. Given the nature of the data ( not required to cache for more than 10
min ), any specific suggestions to make ATS more efficient ?
Well, with such a small cache, 10GB, I'd spend a few hundred $'s and put
it on SSD. It'll make it wicked fast. To use the cache efficiently, tune
the minimum object size setting (in records.config) to be close to your
average / typical size. The default is 8K, which is fairly reasonable,
but if your objects are significantly bigger (or smaller) than this,
you'll use the cache more efficiently by tuning it.
3. As far as I can understand from the documentation, it looks like only
highly used objects will go to Ram Cache. According to that in our use case
only few will
it there. Any tweaks or change in algorithms to move as much as
possible to Ram Cache.
It will only keep the "most used" objects in RAM cache. With such a
small RAM cache as yours, that's probably very few objects, and you are
more likely to suffer from cache evictions happening much more frequent
than you'd want. Again, you ought to have a bigger RAM cache, I mean, a
couple of gig RAM today is like 50 bucks.
If memory is truly a scarce resource, you can try to enable the
compression feature on the RAM. It can save some memory on objects that
are not already gzip'ed.
Cheers,
-- Leif
