# Re: [squid-users] cache_dir ... plz help

From: Scott Anderson <sda@dont-contact.us>
Date: Thu, 01 Nov 2001 15:41:41 -0500

please walk me through the math.

Assuming a average_object_size of 13kb and a L2 value of 256. How do you
get 416?

13 * 256 = 3328
3328 * 256 = 851968

What is wrong with my math?

Henrik Nordstrom wrote:
>
> Right. I must have been seriously sleep deprevated when I wrote the
> message below.. but I wasn't that far off, only 2^2.
>
>
> L1 = cache_dir_size * 2 * 1024 / (average_object_size * L2 * L2)
>
> which when simplified equals to
>
> L1 = cache_dir_size / 416
>
> Regards
> Henrik
>
> Scott Anderson wrote:
> >
> > That does not explain the number 416. If i take 2 * 13 * 256 * 256 this
> > equals 1703936 which is a far cry from 416
> >
> > Henrik Nordstrom wrote:
> > >
> > > timo.dudziak@student.uni-siegen.de wrote:
> > >
> > > > cache_dir [ufs | asyncufs] dir MB L1 L2
> > > > perfect for ext2:
> > > > L2 := 256
> > > > L1 := ceil( MB / 416 )
> > > > so why / 416 ?
> > >
> > > Because someone simplified the calcuation for you by eleminating all
> > > constants.
> > >
> > > L2 = 256 (there is generally no reason to change this on
> > > ext2/ext3/ufs/whatever with a similar directory structure)
> > >
> > > L1 = ceil( MB * 1024 / (2 * average_object_size * L2 * L2))
> > >
> > > MB = size of the cache in MB
> > > 2 = a safety margin
> > > 1024 = conversion factor from MB to KB
> > > average_object_size = 13 KB (farily standard)
> > >
> > > For reiserfs there MAY be a slight benefit in increasing L2 somewhat,
> > > but not too much. There is only marginal differences in tuning this
> > > parameter.
> > >
> > > Regards
> > > Henrik Nordström
> > > Squid Hacker
> >
> > --
> > It is by caffeine alone I set my mind in motion,
> > It is by the Beans of Java that thoughts acquire speed,
> > The hands acquire shaking, the shaking becomes a warning,
> > It is by caffeine alone I set my mind in motion.
> >
> > Scott Anderson

```--
It is by caffeine alone I set my mind in motion,
It is by the Beans of Java that thoughts acquire speed,
The hands acquire shaking, the shaking becomes a warning,
It is by caffeine alone I set my mind in motion.
Scott Anderson
```
Received on Thu Nov 01 2001 - 13:41:44 MST

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