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| Article ID : # | Last review : 2005-12-24 14:30:17 |
| #3034 | Load balancing |
| You can perform load balancing in several ways on Microtechs dns servers using the 'aux' record. The AUX value is most commonly used with MX records. For resillience purposes, most people have more than 1 mail server. This enabled mail to be received at an alternate location if you main mail server fails for some reason. The AUX value will tell other servers which order mail should be tried in. The remote server will use the MX records with the lowest value first. Typically, you'd start at 10, then 20, then 30, etc. Load Balancing The AUX value also has another purpose on Microtech's dns servers, and this is load balancing. If your zone file has more than one ip address for the same name A record we will weight the reponses using the aux value. A low aux value makes an address record more likely to be listed first. The balancing algorithm causes servers with a lower aux to be selected more frequently than those with higher values, although all servers will still be listed first occasionally, as the algorithm is partially random. Records where aux is 0 (zero) will be listed first almost every time. Records where aux is 50,000 or greater will always be listed last. Here is an example of how hosts were distributed on a 100,000 query test against ten hosts with aux values 10-100. The number shown is the number of times that host was listed first: aux 10 51,211 aux 20 21,881 aux 30 10.983 aux 40 6,209 aux 50 3,661 aux 60 2,311 aux 70 1,526 aux 80 1,032 aux 90 675 aux 100 511 Round Robin If your zone file contains more than one address record for the same A record name we will serve them up in a random order each time. Round robin is used only if all the address records found have an aux value of zero. If any of the records have an aux value that is non-zero, load balancing will be used instead. Note that we will also return multiple same-preference MX records in random order, to help equalize the load among same-preference MX hosts. | |
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