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From Leif Hedstrom <zw...@apache.org>
Subject Re: proxy.config.cache.ram_cache.size query from eBay
Date Fri, 21 Nov 2014 16:45:34 GMT

> On Nov 21, 2014, at 9:31 AM, Lerner, Steve <slerner@ebay.com> wrote:
> 
> Thanks for the tips- right now with avg object size set to 32K and RAM set to 64G its
running very nicely… with 1% of the traffic we are interested in (we have to keep in test
until after retail season) we get 5% cache hit rate.
> We’ll try ramping up traffic in January after the retail season and then things will
get interesting. I’ll report in with our stats as we ramp up. We have 2x clusters at 11
machines each with URLS striped across all 22 with URL hashing.


Btw, Phil pointed out to me that I might have been confused about what you define as clustering.
ATS has its own “clustering” feature (named just that), which does basically CARP like
proxy-2-proxy sharing of the caches. What it lets you do is to increase your storage size
by only caching each URL on one box. This is the feature that is also not particularly well
understood or supported :-).

Is that what you mean when you say you have a “cluster” of ATS? Or just a cluster in general
as in 11 boxes behind some sort of load balancing mechanism? The latter is something that
is well understood and supported.

Cheers,

— Leif

>  
> -Steve
>  
> Steve Lerner | Sr. Member of Technical Staff, Network Engineering | M 212 495 9212 |
slerner@ebay.com <mailto:slerner@ebay.com> | Skype: steve.lerner
> <image001.jpg>
>  
> From: Phil Sorber [mailto:sorber@apache.org] 
> Sent: Thursday, November 20, 2014 9:11 PM
> To: users@trafficserver.apache.org
> Subject: Re: proxy.config.cache.ram_cache.size query from eBay
>  
> On Sat Nov 15 2014 at 2:23:13 PM Lerner, Steve <slerner@ebay.com <mailto:slerner@ebay.com>>
wrote:
> Leif,
>  
> Thanks for the response. What we are going for here is gazillions of tiny images- 76KB
average size.
>  
> We’ll try tweaking average object size… what we’d love to do is just have ATS read
from disk only and have minimal to zero RAM at all… with no swapping of course J
> If you want, you can set that RAM cache size setting to 0 to disable it. I think you
will see a noticeable slowdown though, unless your RAM cache has a 0% CHR.
>  
> You will still have memory usage from the directory and other objects, however.
>  
>  
> Old school CDN style- our object library is so massive that this would work for us- and
as we all know its better to serve from disk closer to user than to go over network back to
origin.
>  
> -Steve
>  
> Steve Lerner | Sr. Member of Technical Staff, Network Engineering | M 212 495 9212 |
slerner@ebay.com <mailto:slerner@ebay.com>
> | Skype: steve.lerner
> <image001.jpg>
>  
> From: Leif Hedstrom [mailto:zwoop@apache.org <mailto:zwoop@apache.org>] 
> Sent: Saturday, November 15, 2014 12:10 PM
> 
> To: users@trafficserver.apache.org <mailto:users@trafficserver.apache.org>
> Subject: Re: proxy.config.cache.ram_cache.size query from eBay
>  
>  
> On Nov 13, 2014, at 4:40 PM, Lerner, Steve <slerner@ebay.com <mailto:slerner@ebay.com>>
wrote:
> 
> Hi gang- Phil Sorber referred me to this list.
>  
> We are setting up clusters of Apache Traffic Server to beef up the front end of our image
services which are… large in terms of volume… to say the least.
> We hope to be the big users of ATS and be a strong reference customer- so any help with
is appreciated!
> Our first test cluster consistes of 23 machines, ubuntu12.04, Intel(R) 2x Xeon(R) CPU
E5-2670 v2 @ 2.50GHz, 128G ram, 95T disk
>  
>  
> That is a lot of disk :) With default settings, you would consume roughly 110GB of RAM
just for the indices. The calculation is
>  
>    (95*10^12 / 8000) * 10
>  
>  
> Take comfort that with squid, you would use 10x as much (128 bytes per index entry).
But you have three options:
>  
> 1) increase the records.config setting for average object size. That is the 8000 number
above. Doing so means you can store fewer objects in the cache.
>  
> 2) buy more RAM
>  
> 3) reduce disk capacity on each box
>  
> I thought we had a wiki entry on this subject?
>  
> Cheers,
>  
> -- Leif 
> 
>  
> Here is our query:
>  
> We are setting records.config as: CONFIG proxy.config.cache.ram_cache.size INT 64G
>  
> But we find that trafficserver ignores this limit and grows at the default rate of 1MB
RAM / 1GB disk.
>  
> Example of a current process:
>  
> traffic_line -r proxy.config.cache.ram_cache.size returns 68,719,476,736
> Which is about 64GB- correct!
> 
> But looking at the process:
>  
> 86050 nobody    20   0  108g 102g 4912 S   54 81.3   1523:33 /ebay/local/trafficserver/bin/traffic_server
-M --httpport 80:fd=7
>  
> So basically we’ve set the process to only consume 64GB but its consuming 108GB…
> 
> Does anyone have any ideas on why this happens or a way to fix it?
> We want to have constrained RAM but tons of disk- we’d much rather have the cache serve
from disk then start swapping RAM
>  
> Thanks in advance,
>  
> Steve
>  
> Steve Lerner | Sr. Member of Technical Staff, Network Engineering | M 212 495 9212 |
slerner@ebay.com <mailto:slerner@ebay.com> | Skype: steve.lerner
> <image001.jpg>


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