CM Cluster w 7815 MCS

Unanswered Question
Sep 2nd, 2008

Hi,

While reading UC SRND 6.x (page 270) about CM Cluster meet the statements (both are on the same page):

{

- When deploying a cluster with Cisco MCS 7815 or equivalent servers, there is a maximum limit of 2 servers in a cluster

and

- It is also possible to deploy a single-server cluster with an MCS 7825 or greater servers

}

Am I wrong if suppose 7815/7816 cluster cannot have 1 server (from abovementioned facts) ?

I have this problem too.
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shabali52 Tue, 09/02/2008 - 07:05

It can have one but it only can have a maximum of 2 in a cluster environment.

rob.huffman Tue, 09/02/2008 - 08:22

Hi Tobivan,

I think you are most correct that the 7815 does not have the resources to be deployed in a "single server" environment. I'm going with this clip from the 5.x SRND;

When deploying a cluster with Cisco MCS 7815 or equivalent servers, there is a ***minimum limit of two servers in a cluster: one as the publisher, TFTP server, and backup call processing server, and the other as the primary call processing server. A maximum of 500 phones is supported in this configuration with Cisco Unified CM 5.1 on a Cisco MCS 7815 (or a maximum of 300 phones with Cisco Unified CM 5.0 on the MCS 7815). When deploying a two-server cluster with higher-capacity servers, Cisco recommends that you do not exceed 1250 users in the cluster. Above 1250 users, a dedicated publisher and separate servers for primary and secondary call processing services is recommended, thus increasing the number of servers in a cluster.

It is also possible to deploy a single-server cluster with an MCS 7825 or greater servers. With an MCS 7825 or equivalent server, the limit is 500 users; with a higher-availability server, the single-server cluster should not exceed 1000 users. In a single-server configuration, there is no redundancy unless Survivable Remote Site Telephony (SRST) is also deployed to provide service during periods when the Unified CM is not available. Cisco does not recommend a single-server deployment for production environments. The load balancing option is not available when the publisher is a backup call processing subscriber.

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/5x/50clproc.html

MCS-7815 servers support only N+1 redundancy and may not be a member of a cluster

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/5x/50clproc.html#wp1052905

Hope this helps!

Rob

Tobivan_Helden_2 Tue, 09/02/2008 - 23:00

Hi, Rob.

You are the one of the most effective people as always :)

What do you think about 7816 MCS ?

Will it be possbible to build a single-server cluster based on this model ?

I mean it's strange when SRND version 6.x tells about MCS 7815 which is EoS.

And do not mention anything about 7816 MCS which is an actual standart non-HA server ...

rob.huffman Wed, 09/03/2008 - 05:49

Hi Tobivan,

Thanks for your kind words my friend :) I thought that this was an excellent question so I spent some time looking for a definative answer here. Sadly, like many questions here we are forced to "read between the lines". I did not find any doc that says yes/no to the fact that a 7816 can support a "single server" deployment (even in the new CCM 7.x SRND)

I am going with what I would recommend to a customer and say "no" I wouldn't use a 7816 for this type of build, only a 7825 or higher.

Hope this helps!

Rob

Tobivan_Helden_2 Wed, 09/03/2008 - 23:55

Rob,

Cannot afford myself to disagree with you =)

The life shows that when the documents do not tell

anything about the riddle, the best thing is not

to risk with deployment and do only the things

these documents recommend.

This make the probability that it'll be supported by TAC much greater :)

Tobivan_Helden_2 Thu, 09/04/2008 - 00:19

Rob,

I also have another question. Please, advice, if you know.

1.

The same SRND 6.x (page 270) tells also

{

It is also possible to deploy a single-server cluster with an MCS 7825 or greater servers. With an MCS 7825 or equivalent server, the limit is 500 users; with a higher-availability server, the single-server cluster should not exceed 1000 users

}

Thus I make a conslusion that 7825 can up to 500 users, 7835/45 are capable of up to 1000 users.

2.

In the same doc on the page 282 we can see the table of MCS device capacities.

It show us that

- 7835 can do 2500 users

- 7845 can do 7500 users

I.e. from the one side the doc tells single 35/45 server cluster can up 1000 users.

But up to 2500/7500 users only from the other side. Hm.

Cannot catch up the sense and the difference ...

Tobivan_Helden_2 Thu, 09/04/2008 - 00:46

Rob,

And another question about two-server cluster for 7835 and 7845 MCS.

Does theirs limit equals to up to 1250 devices for the whole cluster

although 7835 can do 2500, and 7845 can 7500 devices ?

It's not so obvious for me.

rob.huffman Thu, 09/04/2008 - 04:47

Hi Tobivan,

No worries my friend :)

The thing to keep in mind here is that the numbers change between a "Single Server" or "Cluster" deployment because of the fact that a single server will have to perform all functions. Callmanager Service,MOH,TFTP etc. etc.. This will use alot of processing power therfore less actual IP Phones can be supported.

In a cluster setup of course these functions are shared between boxes with the use of the Publisher/Subscriber relationship. The Subscriber not being used for other things alows it to support more IP Phones and still have some resources left over to backup in case of failure.

I know that this is probably a tad over simplified but I'm sure you see what I mean here :)

Hope this helps!

Rob

Tobivan_Helden_2 Thu, 09/04/2008 - 06:07

Rob,

What can you say about the specific digits I've asked you ?

Let me to re-formulate the questions if the previous descriptions were too extensive.

1. In the single-server cluster based on 7825 how much devices are possible, 500 or 1000 ?

2. In the single-server cluster based on 7835 how much devices are possible, 1000 or 2500 ?

3. In the single-server cluster based on 7845 how much devices are possible, 1000 or 7500 ?

4. In the two-server cluster based on 7835 how much devices are possible, 1250 or 2500 ?

5. In the two-server cluster based on 7845 how much devices are possible, 1250 or 7500 ?

Dear Rob, I need an exact answers, if you know them. Thank you much.

rob.huffman Thu, 09/04/2008 - 07:55

Hey Tobivan,

Sure thing :)

1.500

2.1,000

3.1,000

4.2,500

5.7,500

These numbers are the "maximum" so if you start to push towards the upper limit a 3 server cluster would be highly recommended.

Hope this helps!

Rob

Tobivan_Helden_2 Fri, 09/05/2008 - 04:12

Rob, thank you.

Still have a little doubt about [4] and [5] questions. SRND 6.x says:

{

When deploying a two-server cluster with higher-capacity servers (higher than 7815), Cisco recommends that you do not exceed 1250 users in the cluster. Above 1250 users, a dedicated publisher and separate servers for primary and

secondary call processing services is recommended, thus increasing the number of servers in a cluster.

}

Based on this, two-server 7835/45 cluster cannot have more than 1250 devices.

But you tell they can 2500/7500 accordingly... I'm totally confused.

rob.huffman Fri, 09/05/2008 - 05:02

Hey Tobivan,

Sorry man! I should have gone with the best practice numbers for a 2 server cluster :( The numbers I gave from are theoretical and are really based on a 3 server cluster (my bad);

Table 8-2 Maximum Number of Devices per Server Platform

http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/5x/50clproc.html#wp1052905

Here is what really matters;

"When deploying a two-server cluster with higher-capacity servers, Cisco recommends that you do not exceed 1250 users in the cluster. Above 1250 users, a dedicated publisher and separate servers for primary and secondary call processing services is recommended, thus increasing the number of servers in a cluster."

Our newest build consists of 3X7845-H2 boxes in a 3 (1 Pub - 2 Sub) server cluster for about 2,500 devices.

I would stick with the 1,250 for a 2 server cluster for sure but I would always recommend a 3 server cluster if at all possible. We also moved the DHCP Server off-box finally to free up resources as well.

Hope this helps my friend, again, sorry for any confusion that I have caused here!

Rob

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