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| <H1 ALIGN="CENTER">Server Pool Management</H1> |
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| We found that many people were using values for "MaxServers" either |
| too high or too low, and were hanging themselves on it. The model we |
| adopted is still based on long-lived minimal-forking processes, but |
| instead of specifying one number of persistent processes, the |
| web-master specifies a maximum and minimum number of processes to be |
| "spare" - every couple of seconds the parent checks the actual number |
| of spare servers and adjusts accordingly. This should keep the number |
| of servers concurrently running relatively low while still ensuring |
| minimal forking. |
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| <P> |
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| We renamed the current StartServers to MinSpareServers, created |
| separate StartServers parameter which means what it says, and renamed |
| MaxServers to MaxSpareServers (though the old name still works, for |
| NCSA 1.4 back-compatibility). The old names were generally regarded |
| as too confusing. |
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| <P> |
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| The defaults for each variable are: |
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| <PRE> |
| MinSpareServers 5 |
| MaxSpareServers 10 |
| StartServers 5 |
| </PRE> |
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| There is an absolute maximum number of simultaneous children defined |
| by a compile-time limit which defaults to 256 and a "MaxClients" |
| directive which specifies the number of simultaneous children that |
| will be allowed. MaxClients can be adjusted up to the compile-time |
| limit (HARD_SERVER_LIMIT, defined in httpd.h). If you need more |
| than 256 simultaneous children, you need to modify both HARD_SERVER_LIMIT |
| and MaxClients.<P> |
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| In versions before 1.2, HARD_SERVER_LIMIT defaulted to 150.<P> |
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| We do not recommend changing either of these values unless: |
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| <OL> |
| <LI>You know you have the server resources to handle more |
| <LI>You use the machine for other purposes and must limit the amount of memory |
| Apache uses |
| </OL> |
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