 Memory
consumption limit
First, thanks for your
answer!
I don't know how to detect how much memory is consumed
by which data...
Anyway, this machine is indeed both slave (authoritative) nameserver
and caching nameserver. Right after starting Bind and loading/transferring
zones from master, there is about 25% of memory consumed. So it
seems like cache is the problem; memory consumation goes slowly
up over days and fills up to 85%. Then the machine acts slow and
drops some requests.
I could buy more memory, but the second server with
1GB RAM suffers from the same problem. I thought 'max-cache' would
keep cache size at least around the limit I've set, but it probably
isn't true.
I'll consider buying another machine and try to
separate authoritative and caching DNS...
Thanks again!
Kevin Darcy wrote:
> How much of that memory is used by the cache,
and how much of it is
> used by authoritative data (you said this was the configuration
from a
> slave)? There isn't a lot you can do about the memory consumption
of
> authoritative data, short of actually deleting records from
your zones.
> For cache, though, you can, in addition to max-cache and
> cleaning-interval -- as you've already tweaked -- play with
> max-cache-ttl and max-ncache-ttl, although do so carefully
because the
> performance impact of lowering your cache hit ratio can be
significant.
> In theory, one can "model" the impact of playing
with max-cache-ttl
> and/or max-ncache-ttl somewhat by analyzing cache dumps and
querylogs
> (anyone care to write a utility to do this?), prior to actually
> committing anything to production.
>
> Ultimately, if you find that your authoritative data is squeezing
the
> amount of memory available for caching, you might want to consider
> separating the caching and authoritative nameservice onto different
> machines. This separation is recommended for security and other
> reasons anyway. Memory usage on an authoritative-only nameserver
> hardly fluctuates at all, compared to a caching nameserver,
so you'd
> just need to size the authoritative-only only box(es) according
to how
> much authoritative data you have today, plus whatever expansion
of
> hosted data you expect in the future.
>
> Another possibility is to recompile BIND with threading disabled.
It's
> possible that a non-multi-threading named might have better
memory
> characteristics on RedHat.
>
> Then again, you could just buy a memory upgrade for the machine...
>
>
>
> - Kevin
>
> P.S. You want a link? Here's a link:
> http://john.redmood.com/osfastest.html. I'm not sure who Jeffrey
> Rothman and John Buckman are, but they seem to prefer Solaris
over
> RedHat for running DNS services. As a moderate-to-strong Solaris
snob,
> I tend to concur :-)
>
>
> Pavel Urban wrote:
>
>
>>Hello,
>>
>>we're running Bind 9.3.1 on RedHat Linux version 3, ES.
After several
>>days we end up with all memory consumed and DNS nearly unresponsive.
>>We have one master and two slaves; this is a part of our
configuration
>>from one slave:
>>
>>options {
>> directory "/var/named";
>> /*
>> * If there is a firewall between you and nameservers you
want
>> * to talk to, you might need to uncomment the query-source
>> * directive below. Previous versions of BIND always asked
>> * questions using port 53, but BIND 8.1 uses an unprivileged
>> * port by default.
>> */
>> #query-source address * port 53;
>> allow-transfer { 194.228.2.61/32; 193.85.7.100/32;
>>193.85.1.12/32; 194.228.1.194/32; 194.228.2/24; };
>> allow-recursion { 127.0.0.1; 194.228/16; 192.168/16;
>>172.16/12; 10/8; 80.188/16; 83.208/16; 85.70/15; };
>> notify yes;
>> recursion yes;
>> max-transfer-time-in 8;
>> transfer-format one-answer;
>> transfers-in 80;
>> transfers-out 80;
>> transfers-per-ns 40;
>> coresize default;
>> max-cache-size 200M;
>> files 1024;
>> stacksize default;
>> cleaning-interval 30;
>> interface-interval 0;
>> recursive-clients 50000;
>>};
>>
>>
>>This is 'top' output from the same machine:
>>
>>46 processes: 44 sleeping, 2 running, 0 zombie, 0 stopped
>>CPU states: cpu user nice system irq softirq iowait idle
>> total 58.2% 0.0% 1.9% 0.5% 1.5% 5.9% 31.5%
>>Mem: 511736k av, 505212k used, 6524k free, 0k shrd, 2988k
>>buff
>> 385208k actv, 72524k in_d, 9404k in_c
>>Swap: 1052248k av, 486172k used, 566076k free 8668k
>>cached
>>
>> PID USER PRI NI SIZE RSS SHARE STAT %CPU %MEM TIME CPU
COMMAND
>>22312 named 25 0 473M 435M 1136 R 59.6 87.2 3610m 0 named
>>22314 named 15 0 473M 435M 1136 S 0.3 87.2 209:11 0 named
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