Wednesday, 25 November 2015

Networks that span multiple Engineered Systems/Exalogic Accounts

This blog post is to introduce some functionality that has fairly recently (~Oct 2015) become available that allows additional infiniband shared networks to be defined.  This enables internal networks to span accounts or be extended to other Engineered Systems.

Historically an Exalogic rack is setup with two internal (IPoIB) networks that have IP addresses which can be handed out to vServers in all accounts, these are the vServer Shared Storage and the IPoIB Default networks.  Any vServers on the storage network are limited members and full members of the infiniband default network. It is possible to override the membership of a virtual machine to allow vServers to communicate to each other internally on the Infiniband storage net.

Security concerns about using the IPoIB default network to allow inter-vServer communication alongside access to the database tier has meant that this network tends not to be used to allow cross-account conversations.   The only other mechanism to allow network traffic between accounts was to use a public EoIB network which has the downside of preventing the Infiniband high performance protocols and mandating the smaller MTU sizes and thus is sub-optimal for performance based applications.

Recent changes in Exadata have introduced support for the use of non-default partitions.  Indeed, when Exadata is setup to make use of the database running in a virtual machine the normal configuration will be such that there is no use of the IPoIB_default partition (0x7fff).   This was a problem for Exalogic which historically only had access to Exadata over the IPoIB-default network.

The standard configuration of a virtualised Exadata is to have two IB partitions, one that allows the database server to talk to the storage servers and another that will connect the virtual machine to another virtual machine on the Exadata so that a distributed RAC cluster can be setup and use IB for inter-cluster communications.  Obviously if Exalogic wants to communicate to Exadata using the Infiniband Optimised protocols the Exalogic must be able to link in with the Exadata over a non-default infiniband partition.  This is depicted in figure 1 below.


Figure 1 - Connecting EL and ED using non-default Infiniband Network

This example shows a two tier application deployed to Exalogic, the web tier which has access to the EoIB client network, potentially hosting an application like Oracle Traffic Director.  This can forward requests on to an application tier over an internal private network and then the application tier is linked to another IPoIB internal network but this is what might be considered a "public private network" meaning that this network can be handed out to vServers and provide linkage to the Exadata virtual machines which have had this specific network (partition) allocated to them.  The Exadata also has two other internal IB networks, one to allow the RAC cluster to communicate between the DB servers and another to allow access to the storage cells.

The approach to creating this non-default network that spans both Exalogic and Exadata introduces a couple of potential options.  Firstly to extend a private network from an Exalogic account into the Exadata rack and secondly to create a new Exalogic customer shared IPoIB network which can span multiple Exalogic accounts.

Extending a Private Network

In this scenario we create a private network within an Exalogic account and then expand the Infiniband partition into the Exadata.  This means that access to the Exadata is kept purely within an Exalogic account.  The steps to go through are:
  1. Create a private network in an Exalogic Account
  2. Edit the network to reserve the IP addresses in the subnet that the Exadata will use.
  3. Identify the  pkey value that this new network has been assigned
  4. Using the IB command line/Subnet Manager make the new partition extend to the Exadata switches and database servers.
  5. Recreate the Exadata virtual machines adding the new partition key to the virtual machine configuration file used.
  6. Configure the Exadata VM to use an IP address made unavailable to the Exalogic

Creating a new "Custom Shared IPoIB Network"

This is a slightly more flexible approach than the first scenario as we create a new "public private" network and then allocate IP addresses on this network to each account that will need access to it.  This is also useful in the use cases that Exadata is not involved because it allows certain virtual machines to be setup as a service provider and others as service consumers.  A provider being an IB full member of the partition and a consumer a limited member.  Thus all consumers can access and use the service provider functions but the consumers cannot "see" each other.

This example is is for the connected Exadata that we discussed earlier.  In this case the process to follow is:-

  1. Run the process to create the new IPoIB network.  It can be setup such that all vServers will be limited or full members by default, defines the IB Partition and specifies the subnet used as well as which IP addresses the Exalogic rack will use.
  2. Allocated a number of IP addresses from this new network to each account that will use it.  Same process that is used for EoIB networks, storage network or the IPoIB Default network today.
  3. Create vServers in the accounts with an IP address on the custom shared network.
  4. Identify the pkey for the custom network and extend the partition to the Exadata switches and DB server nodes.  The primary difference here is that if the Exadata was setup first then the first step in this process would have been to specify the pKey that was originally used by the Exadata.  (i.e. Either the Exadata or the Exalogic can be the first to specify the pKey.)
    1. Warning - The pKey being used is defined manually.  Make sure it will not overlap with any pKeys that Exalogic Control will assign.
  5. Recreate the database virtual machines assigning the pkey to their configuration and within the VM specify the IP address you want them to use.  
  6. Test 
Note - The technical details on how to achieve this are fully documented in an Oracle support note.  Get in touch with your local Oracle representative find out more.

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