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meritel1025
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DNS cache size and timeouts - v3

Sat Sep 15, 2007 7:28 pm

For release 3, can you PLEASE allow an increase in the DNS cache size? There really isn't any reason why it should be limited to 10MB. If you are going to create a hard limit, 1GB should be more than plenty for the average ISP using MT software. We set the max cache size on most of our other DNS servers to 500MB.

I like using the MT as the primary DNS server as it makes for simpler setup and troubleshooting with clients. I know, however, that 10MB is not enough and there have been occasional delays in going out to search when the cache is full.

Also, it would be nice to have a timeout override for how long data is kept in the cache. Some data is in the cache for a long time as configured by the domain's DNS admin. Some of these sites are not frequently accessed and we would like them dumped after a shorter period so there is more room for more commonly visited sites. Being able to set a maximum time that a record is cached without being re-accessed would be great. For example, setting a max record cache time to 1 day would drop infrequently visited sites after 24 hours, but site which are commonly requested would keep having their timer reset.

Thanks,
Steve
 
Znuff
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Re: DNS cache size and timeouts - v3

Sun Sep 16, 2007 2:54 am

Having THAT BIG DNS caches is stupid. Why? Because the world keeps changing. Websites update their DNS every day.

10MB is MORE than enough, considering that 256Kb of DNS cache can hold more than 1000 entries. I've never seen my DNS cache max out at 10MB, even for a month of uptime.
 
meritel1025
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Re: DNS cache size and timeouts - v3

Sun Sep 16, 2007 6:05 am

Perhaps when your network grows up, then you'll understand what kind of traffic big companies have. Your 3 computers on your network may not use up but a few hundred kb, but thousands of computers request a bit more traffic.

With regard to changing DNS daily, not true. I guess the porn sites may, but most major sites do not. "Gee Bob, did you remember to change all of the IP addresses for our servers today? You know how the bosses here at CNN.com hate having their customers be able to find them each day. Let's make sure that we change our IP addresses so that the replication process never stops."

Also, when you learn how to read, or understand DNS, you'll understand why I said that the cache needs an override so that we can set the max timeout for a record to be 24-hours. I don't want the records to remain longer than a day.

I guess not understanding that not every network is the same or has the same needs is why you quickly throw out the word stupid.

Now, go back to your room, get out your G.I. Joes, and let the grown-ups talk.
 
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warwick09
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Re: DNS cache size and timeouts - v3

Sun Sep 16, 2007 9:13 am

You people are funny .... as to your DNS issue; one word - BIND. Its your savior, use it wisely.


Regards.
 
Znuff
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Re: DNS cache size and timeouts - v3

Sun Sep 16, 2007 5:24 pm

1st of all I have more than 200 computers.

2nd a max-timeout shouldn't be user configurable - that's why we have an option to specify the TTL, refresh, retry etc. values for our domains.

When I'm talking about DNS changes, I'm reffering to websites that move for a reason or another. DNS is a very dynamic protocol.

Ever wondered why the guys at BIND never implemented that save-to-disk cache in their software that people keep asking for?

And relax a little more, I have more DNS experience than you.
 
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macgaiver
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Re: DNS cache size and timeouts - v3

Mon Sep 17, 2007 2:28 pm

Do not confuse DNS cache with DNS servers - DNS cache do not need any timeout overrides.

About size - it is not depending on network size. For example:
100 office workers might use only 50 different web pages in the working hours, but 20 home users can use more than 200 different

One way or another in any size network you will not find usage for more that 100 popular web pages. So few Mb are OK.

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