Load balancing with failover questions

If we install 2 multi-role Exchange servers in our building and a 3rd multi-role server in our remote data center, what is the best way to load balance them? Do we need two load balancers or is there some way to span a single load balancer across the
WAN ?
What about using Windows NLB as an alternative to using round robin internally?
Can a load balancer keep our interoffice Exchange CAS traffic from leaving our LAN and only failover to using the 3rd CAS/mailbox sever for internal users if both internal Exchange servers are offline?
We would also like remote users to "prefer" to use the data center CAS unless it is down. Right now we point our smart host directly to a CAS, but if we had a load balancer there, we could point the smart host to the IP of the load balancer and
the load balancer could normally send it to data center CAS if it's up and forward it to one of the servers in the office otherwise.
Is it possible to do all this without a very complicated and expensive solution?

Depends... what is the connectivity speed between two sites, is it good enough?
You can use load balance in front of all the 3 CAS if your inter-site connectivity is very good.
What about using Windows NLB as an alternative to using round robin internally? WNLB and round robin is different,. You can use DNS Roud Robin if you want to or WNLB for all three CAS Server. Or Hardware loadbalancer for all three CAS servers
Can a load balancer keep our interoffice Exchange CAS traffic from leaving our LAN and only failover to using the 3rd CAS/mailbox sever for internal users if both internal Exchange servers are offline? If you want to use the load balancer then you don't
need to fail them over one by one -- again you can use DNS Round Robing so the request will go to eah CAS servers one by one or use Hardware Load balance.
We would also like remote users to "prefer" to use the data center CAS unless it is down. Right now we point our smart host directly to a CAS, but if we had a load balancer there, we could point the smart host to the IP of the load balancer and
the load balancer could normally send it to data center CAS if it's up and forward it to one of the servers in the office otherwise.
Use DNS Server and point the A record to the Primary Data center load balanced CAS server instead using IP or host file.
Hope that helps
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Two Wireless controllers load balance and failover question

I have two 4404 controllers and each can take 100 APs. I have 140 APs in total. With the default settings (no master controller, no configuration of Prime, secondary controller on APs), each controller will take 70 APs, right?
Then I will need to configure each AP with an IP address, name ...etc. My question is, when one Controller failed, these 70 APs will try to associate with another controller, right? However only 30 APs can because another controller can maximum manage 100 APs. Then in this case, will these 30 APs lose their static IP addresses and names? When the failed controller came back online, will the 70 APs automatically go back to this controller and have their IP, name configuration back?
Thanks!

With default setting you have no control how many ap's go to what wlc. It doesn't matter, because you will need to specify the primary and secondary. You might as well stage all the ap's you want on one wlc first and set that wlc to master, then when you have finished that, set the other wlc to master and have the ap's join that wlc which will be the primary fro those ap's.
You only can support 100 ap's so depending what code you use, 30 ap's that are not able to join will just keep trying. If you run 5.2 (I think is buggy) you can set the priority on the ap's so that ap's that you set up with a higher priority will be able to join and the others will again sit there until the othe wlc comes back up. Static IP address will not dissapear because the wlc doesnt' accept any more connections. Once both wlc are up, the ap's will go back to their primary wlc as long as ap fallback is enabled and mobility is configured right.

Load Balancing with BigIP / SSL question

I have an oddball question. We're load balancing ColdFusion
MX7 across 3 servers using a BigIP load balancing server. We
decided to go the hardware approach and it has been great except
for one small configuration issue.
We use a mix of SSL and non SSL pages, prior to the switch
from a single server to a load balanced setup I used to script that
would determine if a page that was supposed to be SSL had the
variable CGI.HTTPS turned on or off. If it was off, the page would
redirect back to itself with the SSL turned on.
The problem we have is that we followed BigIP's instruction
to secure the load balancing hardware instead of the three servers
running behind it. So what happens is that the traffic goes to the
load balancer port 441, but then the calls from the load balancer
to the individual servers is port 80. So even if a page is called
as HTTPS://... the coldfusion server says that CGI.HTTPS is "off"
since the traffic is port 80.
This isn't much of a problem, our SSL pages are linked as
HTTPS:// and the only problem would actually arise if someone was
to type in the URL and call it as HTTP rather than HTTPS.
My questions is this, does anyone know of a way that I can
detect if the page should be HTTPS and is not without changing our
configuration and putting SSL certificates on each individual
server?

Hey,
Well the load balancing with the BigIP device is really very
amazing. I think
what i liked most was swapping out servers when their lease
was up, through the
BigIP manager I just stopped all traffic to a server, shut it
down, plugged in
the new one and turned traffic back on. It was really very
easy.
The SSL stuff still gives me a headache to think about. but
I should mention I
no longer work where I was, plus now I'm all .net C# but
that's a different
story.
I think if I was going to do this all again I would not have
secured the bigIP
unit. It was nice to buy one SSL cert for all the servers I
attached rather
than one per server, but getting the SSL sites to work
properly was a headache.
We also use windows file replication where now I would go
with like a pair of
Dell MD1000's mirrored for storage and just have tons of ram
and cpu on the
front end units. Depends what you want to spend I guess. I
think the bigIP unit
we bought was like 20 grand, i think they are cheaper now
though.
Hope I helped.

Load Balancing and Failover with 10G Standard Edition

Hi,
I am new to Oracle Replication and need some help setting up replication for load balancing and failover. Is this possible using Oracle 10G Standard Edition? I plan on having all updates done on the master site and both databases will be for reads. In case of failure of the master site, I would need to be able to failover to the other database.
Also, if anyone knows of any documention for Basic Replication in 10G, please let me know.
Thanks.

Simple nnapshot replication of data would require significant manual effort to configure to load balance or failover. One the load balancing side, you would generally be limited to to static load balancing-- assigning half the users to one machine and the other half of the users to the other machine, regardless of who is actively using the machine. Failover would be a significant manual effort, particularly to bring the failed machine back into the cluster. You would be implementing the guts of multi-master replication.
Frankly, if you actually have a system which is valuable enough to need load balancing and disaster recovery, I'm going to wager that it will be far cheaper even in the short run to buy more boxes and/or enterprise edition licenses than to try to implement this sort of thing yourself. In the long run, it will be far cheaper, since it will be far easier to maintain. Building all this yourself would probably be penny wise and pound foolish.
Justin
Distributed Database Consulting, Inc.
http://www.ddbcinc.com/askDDBC

IChat Load Balancing or failover solution?

Hello, I am working a plan to develop a iChat server. I think a Mac Mini would be a good start for a group of 50 users. The users are all over the country and my role is to unite them all in a iChat domain. I thought about building two Mac Mini servers and have them run a same domain where all users are registered in. So, we would not be impacted when one of them goes down.
Anyway, the question is how can I have a load balancing or failover solution for the iChat domain?

On the issue of load balancing, whilst I don't have any experience with macMini's, you will not need to worry about load balancing with 50 users. I'm sure you can probably put a few naughts on the end of that before you need to worry.
The design you are proposing will not work for iChat services / and for that matter most of Apple server services. For high availability services (e.g. transparent failover) I think you are going to struggle to get this working and it 'seems' Apple no longer offers guidance on this subject on 10.6.x.
You will increase availability by using an Xserve with dual PSUs and raid disks. If you are only running high availability ichat services, I would buy a pair of second hand xserves with 10.5 OS and set the ipfailover services running. Personally I would buy one and a service kit and not bother with HA - as you will find the servers are very reliable.
If you have to use mini's then just have one live and keep a near constant clone of it on another ready to manually swap out if you have a hardware failure.
Your proposed design will not work without a lot of effort non of which is supported by Apple - although it would be rewarding if you did get it working. You cannot have server to server traffic for the same domain as all your application data needs to be stored centrally. OD only provides services for authentication. The ichat server also has its own data store and this is not distributed nor can it be. It is possible to move the data store over to say an enterprise version of mysql and have that distributed.

Load balancing and Failover

Hello,
We are wondering how load-balancing and failover of tpcall() work with
WTC:
The scenario:
We have one WLS Domain and two Tuxedo Domains. The Tuxedo Domains offer
the same set of services.
In the bdmconfig.xml, we specify connection_policy as 'ON_STARTUP' for
both Remote Tuxedo Domains. We also Import (T_DM_IMPORT) the same
Tuxedo Service from both Tuxedo Domains.
Questions:
1. Is there any load-balancing of the tpcall between the two Domains? If
so, is it round-robin? If round-robin, what determines the order?
2. If it is ONLY Failover, what determines the order of the tpcall? And,
is the Failover automatic? Or do we need to code for retry on failure?
3. ON_DEMAND vs ON_STARTUP: Does ON_DEMAND drop the connection to the
remote domain upon tpterm? And does ON_STARTUP use a pool of
TuxedoConnection objects?
4. Are there any configuration parameters for
'max_number-of_connections? What determines how many simultaneous
connections can be made?
Thanks,
Suresh Mohan.

Hi Suresh,
The following are my answers to your questions.
Suresh Mohan wrote:
Hello,
We are wondering how load-balancing and failover of tpcall() work with
WTC:
The scenario:
We have one WLS Domain and two Tuxedo Domains. The Tuxedo Domains offer
the same set of services.
In the bdmconfig.xml, we specify connection_policy as 'ON_STARTUP' for
both Remote Tuxedo Domains. We also Import (T_DM_IMPORT) the same
Tuxedo Service from both Tuxedo Domains.
Questions:
1. Is there any load-balancing of the tpcall between the two Domains? If
so, is it round-robin? If round-robin, what determines the order?Yes there is a load balancing between two remote Tuxedo TDomain Gateways.
The algorithm is random, not RR. Over time this should give equal
opportunities to both remote TDomain.
>
2. If it is ONLY Failover, what determines the order of the tpcall? And,
is the Failover automatic? Or do we need to code for retry on failure?The load balancing is always there. The failover is automatic. When a
connection to a remote TDomain encountered a problem (ie network) the remote
domain will be put on retry open connection (in ON_STARTUP) and the load
balancing will not select it until the connection re-established.
However, the tpcall() that encountered the error will not be retried to send
to different destination. It is up to the application to decide whether it
want to resend. Any requests called after the error will not select the
failed Remote TDomain.
>
3. ON_DEMAND vs ON_STARTUP: Does ON_DEMAND drop the connection to the
remote domain upon tpterm? And does ON_STARTUP use a pool of
TuxedoConnection objects?TPTERM() only terminate your application session to WTC. WTC still maintain
a secured T-session to remote Tuxedo TDomain. WTC does not use a pool of
TuxedoConnection Objects, the object stored in the JNDI refers to WTC.
>
4. Are there any configuration parameters for
'max_number-of_connections? What determines how many simultaneous
connections can be made?No. As described in #3, there is no need to use connection pool in WTC. WTC
uses session and virtual circuit design concept as Tuxedo TDOMAIN, the
logical pool is created/destroyed dynamically. That is the reason why you
can have a lot of TPACALL() outstanding at the same time. (The limitation is
the availability system resource.)
>
>
Thanks,
Suresh Mohan.Regards,
Hong-Hsi :-)

Multihomed eBGP load balancing with 3 ISP's

We currently peer with 2 ISPs using BGP in an active/failover configuration. My company wants to move to a 3 ISP model where Internet traffic is split across the 3 providers so that bandwidth is equally distributed on outgoing traffic across our 2 /22 ARIN IP ranges. This is from our 2 edge switches that have VSS.
Within my limited knowledge of BGP, I have determined that we could do load sharing pretty easily by adding multiple default routes and breaking up our /22's into /24 and advertising them that way. However, I don't think this satisfies the request that downtime must be seamless, should one link drop.
Currently, our ISP's advertise default routes. From the research that I've done, we could get close to load balanced links if we receive full BGP routes and community settings and definitions. I'm nervous about this because it looks really complicated, and I don't want our AS to turn into a transit AS. I've been told the same can be accomplished with only partial BGP routes and community settings and definitions.
Personally, I think we just need a WAN load balancer. However, given the request, is there a thread out there that can explain this, or can someone discuss this requested scenario a little bit?
Thanks!

Hi there
First question would be what is the required reconvergence time for the applications using the Internet? Should an outage occur, when do they lose their state? Once you know that, you then have a target to aim for in terms of recovery
With regards load-balancing, with BGP we are always talking inbound and outbound.
The outbound solution is relatively simple - each ISP advertises a default route to your Internet edge router(s). Create an eBGP session from each edge router to the core, advertise the default route and redistribute into the IGP. Ensure the IGP cost to each BGP next hop is equal and you have ECMP for outbound routing.
Inbound influence is usually via MED (not likely in this case given 3 ISPs), adjusting local-pref in the ISP via BGP EXT communities configured your end, or via AS-PATH prepending for longer prefixes from your /22. Prepending would be simplest, but your unlikely to get an exact inbound traffic split, however a relatively even distribution should be sufficient.

CF 10 Load-Balancing with Remote Instances

I was reading an article on Clustering/LB/HA using CF8, but have not found any updates for CF10.
Using VM VirtualBox to setup a few virtual servers, I am looking to setup a load balancing of ColdFusion 10 on 2 remote instances. The goal would be have ColdFusion Cluster Manager be able to point http request to one of the two servers based on load/availability. Not really having a hardware cluster/failover setup, just managing resources on two CF instances instead of a standalone.
The servers are Windows Server 2008 R2 with IIS7.5 and ColdFusion 10 Enterprise on installed on 3 of these machines. Let's call them CF-LBManager, CF-Web1, and CF-Web 2. In the CF Docs, they show the Cluster Manager adding the local CF instance and "if you want" a remote instance. However, this scenario would require the main instance to be running and not fail for it to direct to the other instance.
I am trying to set this up now with CF-LBManager as just a manager of the requests coming in. In the Enterprise Manager >> Instance Manager, the local instance is shown and I add the two remote instances with the correct Remote Port, JVM Route, etc. I also made sure the <Cluster>...</Cluster> block was added to the two remote instances (CF-Web1 and CF-Web2) \runtime\conf\server.xml file too, Jetty Services also is running. Now under the Enterprise Manager >> Cluster Manager I add the two remote instances to the cluster, not the local instance on CF-LBManager with Multicast Port and Sticky Sessions enabled. On Submit, I get a green message "You must restart all the server instances and any configured webservers for these changes to take effect.". I go ahead and reboot the servers and come back.
I now browse to the ColdFusion page as a test on CF-Web1 and CF-Web2 to make sure CF is running properly, they do. I then browse the IP of the CF-LBManager, however it only returns the local IIS web site and not redirect to one of the two cluster members. I am not seeing any message on the coldfusion-out.log on the remote instances. Am I not setting this up correctly or not enabling the Cluster Manager to take over and pass along the requests to those in the cluster?

Unfortunatley I don't have a lot of experience with CF10 on Windows, but if you are running CF behind IIS I think you will need to update the Tomcat connector configuraiton to do load balancing. I'm not sure if re-running the wsconfig tool on all of the servers will do this or not, but that is what I would suggest trying first. If that doesn't work you will need to update the Tomcat connector configuraiton manually. You can find more information on load balancing with the Tomcat connector here: http://tomcat.apache.org/connectors-doc/generic_howto/loadbalancers.html.

Cache and Load Balancing with Oracle APEX Listener

Hi,
I intend to use only HTTP access.
How to implement a Cache and Load Balancing with the Oracle APEX Listener?
Is it possible to do with the the standalone running APEX Listener?
Thanks by advance for any tips/documentation/references.
Kind Regards.

Hi,
I think this question is best asked in the APEX Listener forum:
ORDS, SODA & JSON in the Database
Kind regards
Sandro

JDBC load balancing with non RAC replicated instances

Hi,
The thin JDBC load balancing feature only works with RAC clusters or it can be used with two non RAC replicated instances using the same service name?
Thanks,
Ezio.

Thank you Douglas for your time.
I assumed the first case (database connection load balancing). I thought that the listener would do the load balancing and failover trick. So, I configured the JDBC connection as follow:
String MM_loadBalance1_DRIVER = "oracle.jdbc.driver.OracleDriver";
String MM_loadBalance1_USERNAME = "scott";
String MM_loadBalance1_PASSWORD = "tiger";
String MM_loadBalance1_STRING = "jdbc:oracle:thin:@(DESCRIPTION=" +
" (LOAD_BALANCE=on) (FAILOVER=on)"+
" (ADDRESS_LIST="+
" (ADDRESS=(PROTOCOL=TCP)(HOST=test1) (PORT=1521))"+
" (ADDRESS=(PROTOCOL=TCP)(HOST=test2)(PORT=1521)))"+
" (CONNECT_DATA=(SERVICE_NAME=test)))";
Driver DriverRecordset1 = (Driver)Class.forName(MM_loadBalance1_DRIVER).newInstance();
Connection ConnRecordset1 = DriverManager.getConnection(MM_loadBalance1_STRING,MM_loadBalance1_USERNAME,MM_loadBalance1_PASSWORD);
But, when one of the instances was down (test1), the connection failed, it didn't failed over to the other instance (test2).
So I wondered if it failed due to some misconfiguration issue or because it only works with RAC instances...

How does load-balancing with WebCache work - is there still a bottleneck?

Hello,
We're migrating an old Forms 6i app to 10.1.2.0.2 (apps servers = Redhat Linux), and are starting to consider using WebCache to loadbalance between two application servers.
My question is this - say we have apps servers A and B, both running Forms and Reports Services. We use Webcache on server A (don't have the luxury of a third apps server...) to load balance between A and B. So all initial requests come into A, which in some cases may then be diverted to start a new Forms session on B.
For those users whose middle-tier sessions are now running on B - will all network traffic for their Forms session continue to be routed through Webcache on A, then to B, over the course of the session? Or does Webcache somehow shunt the whole connection to be straight between the client PC and server B, for the duration of that Forms session?
If the former, does that mean that the server hosting Webcache can still be a significant bottleneck for network traffic? Have people found load-balancing with Webcache to be useful..?
Thanks in advance,
James

Hi gudnyc,
Thanks for posting on Adobe forums.
For HDPI you do not have to do any It will adjust automatically.
http://helpx.adobe.com/photoshop-elements/using/whats-new.html
Regards,
Sandeep

Load balancing and failover in Embedded LDAP in weblogic

How to handle load balancing and failover in Embedded LDAP in weblogic server?

You should consider posting this to the Weblogic and/or LDAP support forums. This forum is meant for Sun Web Server questions.
Thanks
Manish

CSS Load Balancing with Cookies

We are trying to load balance 2 backend servers hosted on Websphere with advance balance cookies method.
Restrictions
ServerA is unable to accept cookies generated from ServerB.
ServerA and ServerB are generating random cookies
Unable to modify cookie string with a constant.
How can we load balance based on cookies considering the above restrictions?
We have attempted to do hash based load balancing with cookies but the problem we run into is the servers do not accept cookies generated from another server.
The configuration we tried is written below:
service ServerA
ip address 192.168.10.2
keepalive type tcp
keepalive port 80
active
service ServerB
ip address 192.168.20.2
keepalive type tcp
keepalive port 80
active
content ABC
url "/*"
add service ServerA
string prefix "JSESSIONID="
advanced-balance cookies
port 80
add service ServerB
string skip-length 5
string process-length 16
string operation hash-xor
protocol tcp
vip address 172.16.32.1
active
Can we change the string prefix to JSESSION instead of JSESSIONID= ?
The only place the app guys can add a constant string to match on is before the = sign.
Is it possible for CSS to match on a constant string before = sign e.g below:
service ServerA
ip address 192.168.10.2
keepalive type tcp
keepalive port 80
string id567=
active
service ServerB
ip address 192.168.20.2
keepalive type tcp
keepalive port 80
string id123=
active
content ABC
url "/*"
add service ServerA
string prefix "JSESSION"
advanced-balance cookies
port 80
add service ServerB
string skip-length 0
string process-length 6
protocol tcp
vip address 172.16.32.1
active

It should work.
There is no reason for it not to work...
This is the best method you can have on the CSS for stickyness.
Get a sniffer trace on the client and server with arrowpoint cookie configured on the CSS and capture a failure so we can see what is going on.
also send me the config so I can verify everything is ok.
If you have a service request open with the TAC, you can also give the SR # so I can review what has been done.
Gilles.

Load balancing with JSP

Anyone and everyone,
When configuring load balancing with Weblogic clusters, does load
balancing take effect for all services or just EJB and RMI? Or another
way of saying the same thing, can I setup weighted load balancing for
the JSP engines across 2 weblogic servers.
Thanks in advance,
Mike

The load-balancing documentation you read describing the different algorithms only applies to RMI stubs (e.g., EJB clients). Please see http://www.weblogic.com/docs51/cluster/concepts.html#1026091 for a description of how load-balancing/clustering works with servlets/JSPs.
The short answer is that in using servlet clustering, most people want/need/use in-memory replication for HttpSession objects. In WLS 5.1 (and before), in-memory replication requires one or more proxy servers be set-up in front of the cluster. Typically, most people use something like BigIP to load-balance
across the proxy servers and let the weblogic plug-in for the proxy server handle the routing to the cluster. The plug-in uses round-robin until an HttpSession is established for a user, then it always tries to route to the server where the user's session is located.
Hope this helps,
Robert
Brian Lin wrote:
All,
I have a quesiton here regarding load balancing with DNS round robin. As of Chapter Adminstration of Clustering Weblogic server, Weblogic can be configured to balance by weight. How about Weblogic handle weight based balancing after DNS round robin ip response? or just can choose one way instead of both?
What's the big difference between choosing BigIP and software balancing (WL)?
Brian
"Wei Guan" <[email protected]> wrote:
I don't think you can configure this load balancing in weblogic in current
release. However, if you have Big-IP or LocalDireoctr, you can set up
weighted load-balancing there. Otherwise, weblogic proxy will use DNS round
robin to do the load-balancing between JSP engins.
My 2 cents.
Cheers - Wei
Michael Yakimisky <[email protected]> wrote in message
news:[email protected]...
Anyone and everyone,
When configuring load balancing with Weblogic clusters, does load
balancing take effect for all services or just EJB and RMI? Or another
way of saying the same thing, can I setup weighted load balancing for
the JSP engines across 2 weblogic servers.
Thanks in advance,
Mike

Load Balancing With Round Robin

Hi,
I have two iAS instances, each on their own box, and one iWS instance
running on a third box. I have setup the web connector to use round
robin and added the server weights. I believe that is all that is to it
to do simple load balancing with iAS. The problem is is that the
requests only go to one iAS instance. The server weights are 1 and 1.
Am I missing something here?
Thanks

Could be lots of things.
The most common misconfiguration is testing an application that is deployed "local". This application option effectively disables load balancing.
Another common mistake is to either not update the configuration of the webconnector (if the webconnector
has a seperate configuration LDAP) or to not restart
the webconnector after the configuration change.
Hope this helps. There's more things we could try, but I'll hope its one of these two easy things.

Load balancing with failover questions

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