Le mardi 06 septembre 2011 à 16:15 +1200, Amos Jeffries a écrit : > On Mon, 05 Sep 2011 20:23:02 +0200, David Touzeau wrote: > > Dear > > > > I would like to create a kind of law calculation in order to quickly > > calculate server performances to store squid... > > > > I know there is a lot of parameters that should make e this > > calculation > > more complex, but this is just to be generic. > > > > "generic" is not possible. It boils down to what _your_ users are doing > is different to _my_ users. > > > > For example : > > > > I have 150 users : > > ----------------------------------- > > > > Memory : 750K per users = 150x750=112 Mb memory + 300Mb for the > > system = > > 512 Mb minimal. > > Hard disk cache : 50Mb/user = 150*50 = 7.5Go minimal stored disk > > size > > for cache.. > > > > Is it make sense ? > > Your aim makes sense in a way. The metric of "per user" does not relate > to resource usage though. > > This is solely because one user could be making no requests at all or > several thousand per second. And they can switch between these > behaviours and random values in between without notice. I have seen a > network happily serving 15K users with one Squid on a 50MBit uplink, and > also a GigE network brought to its knees by just a few users. "Normal" > web traffic in both cases. > > > The Squid relevant metrics are closer tied to requests per second, or > the internal Mbps line speed of HTTP requirements. > > > Minimal stored disk size is always zero. Maximal is best at <80% of the > size of the disk you plug in. Moderated by at most 2^24 objects per > cache_dir. This is a fixed limit, so performance there is relative to > your average cacheable object size. Disks are best sized along the > lines of: 2^24 * avg object size. Overall disk count multiply that out > by req-per-sec to the time you want things cached by or run out of $$ to > buy disks. > > > Memory consumption is dominated by the disk index (10-15 MB index / 1 > GB of storage). And by cache_mem storage, which will suck up every spare > byte you can give it until itself starts to suffer those 2^24 object > limits. per-User/connection requirements are measured in KB, so these > days not really worth worrying over. > > > Amos > *Many thanks Amos It is clear.... A kind of simple law should be useful when an IT need to know quickly which server can be ordered according users number but i'm agree with your arguments...
