Application Availability Blog

Blog Entries in Continuous Availability

Monday, September 21st, 2009 - 9:40 am EDT

Q&A: Windows Server High Availability

Posted by: Michael Bilancieri

Thanks again to those who joined us for last week’s webinar, "Windows Server 2008 High Availability: Technology Comparison." The on-demand recording of last week's webinar is now available to watch at your convenience (here).

We had a lot of good questions from our attendees during the Q&A portion of the webinar, which are summarized below.

Q: How do you determine when to use an HA solution vs. a DR solution?
When it comes to availability vs. recovery, the most important question to ask is what are your recovery time objectives (RTO)? What is the amount of time your application can afford to be down? If the applications have strict requirements, then you want an availability solution. Disaster recovery is data replication often times with a failover capability, not availability. For critical applications, this may not be sufficient.

Q: If I have an HA solution in place, do I still need a solution for backup?
Availability and backup are two different things. That question comes up a lot, along with the need for disaster recovery. Backup will never likely go away completely. You still need to backup your data to ensure recovery in the future should that be necessary.

Q: Is everRun available for Linux applications?
Yes. We can provide basic failover capabilities for Linux applications today.

Q: How does everRun differ from replication solutions?
everRun 2G is used for availability, both locally and for short-distance geographic separation as well. We have a replication and recovery solution as well that can be used for disaster recovery for long distances. You should determine what your objectives are: do I have to keep my applications up and running or do I just need to recover it if something fails? What’s the recovery time objective for each application? It’s up to your individual applications and what level of protection you need for each. Often times availability is a priority as downtime is not desirable, with DR also a requirement on top of that to ensure recovery in the event of a major outage.

Q: Can everRun be used for planned downtime (i.e. to keep one host running for end-users while the application on the other host is being upgraded)?
Yes, everRun can be used to help facilitate certain system updates to reduce interruptions and mitigate risk.

Q: Can it work between two virtual machines and on x64 based systems?
Yes, we support XenServer and 64-bit hardware and Windows Server environments.

Q: What is the performance impact of using everRun 2G?
That’s variable depending on your application. It can be anywhere from 3-15%. We’ve done some performance testing specifically on XenApp and Exchange. You can download those white papers here:
Understanding and Characterizing Performance Implications for Running Exchange 2007 with everRun
XenApp 5.0 High Availability Performance

Q: Does Marathon offer backup solutions for everRun users?
We have methods to backup your systems and we’re working improving on our current offerings to make them quicker, easier and more granular.

Q: Can everRun work with dissimilar hardware? Can everRun work with more than two servers?
From a server standpoint, you just need similar processors; storage does not need to be similar. You can have SAN on one side and NAS on the other or any other combination. On the second question, yes, everRun will work with more than two servers. You can build a pool of servers and protect within that pool.

Q: Does everRun have backward compatibility with older OS?
Yes. It will work with Windows Server 2003, and also Windows Server 2008.

Q: Can everRun run on the Foundation Server Edition of Windows 2008?
It does not. everRun supports the full implementation of Windows Server 2008. everRun runs underneath Windows, it does not install into Windows.

Q: How does everRun handle data stored on NAS?
Storage is transparent to everRun. We look at storage as just a LUN.

Q: What is difference between everRun HA and everRun 2G in Windos Server 2003?
The differences are the ability to create multiple workloads. HA can protect one workload. everRun 2G can protect multiple workloads. There is also a new and improved graphical interface with better reporting and management capabilities.

Q: Does everRun work with XenServer 5.5?
Yes, everRun works with XenServer 5.5.

Q: Are there any changes in WS 2008 & WS 2008 R2 in the way that HA improves?
Yes. You can find an overview of those changes directly from David Hanna of Microsoft in our recent webinar and white paper “The Top 10 Reasons to Upgrade to Windows Server 2008.” You can also read the Q&A with Microsoft from that webinar here.

Q: Is everRun 2G available for Microsoft Hyper-v?
We will provide support for Hyper-v in a future release.

Q: With applications using various DNS names, how does this solution integrate with DNS changes? (failover to remote office for true DR-different IP/network)
everRun availability solutions pairs systems within the same subnet of vLAN, eliminating the need to make any DNS changes.

Q: Question is tied to what permissions are needed to do a recovery. For recovery in active Directory most items need to replicate around that there was a change and we do not want to hand out Admin control over the domain(separation of access)
everRun is designed to not require any changes to Active Directory during or after a failure or recovery.

 

Show Discussion / Comments (0)
Availability  Continuous Availability  Data Replication  Disaster Recovery  EverRun  Fault Tolerance  High Availability  Marathon  Webcast  Webinar  Windows  Continuous Availability  Data Replication  Disaster Recovery  EverRun  Fault Tolerance  High Availability  Marathon  Webcast  Webinar  Windows  Availability  Fault Tolerance  High Availability  Webcast  Webinar  Fault Tolerance  High Availability  Webcast  Webinar 

| More



Tuesday, August 4th, 2009 - 10:59 am EDT

Q&A from the Windows Server 2008 webinar

Posted by: Brian Mullins

Our July 30th webinar “Top 10 Reasons to Upgrade to Windows Server 2008 Now” was very well attended, and as expected, generated a lot of good questions. So many questions, in fact, that we weren’t able to answer them all during the live Q&A portion of the webinar.

For your convenience, we’ve captured all of the questions below. Answers have been provided by our speakers, David Hanna, Infrastructure Architect at Microsoft, and Michael Bilancieri, Senior Director of Products at Marathon. The questions are grouped by topic, starting with Windows Server related questions and then Marathon everRun related questions following after.

How seamless is the migration from Windows Server 2003 to 2008?
It really depends on the workload. Active Directory upgrade is similar to the 2000 to 2003 upgrade, and should not be disruptive. Cluster migrations require a rebuild of the cluster. For IIS, many applications can be migrated easily. It’s best to look on Microsoft.com for migration info that is specific to your workload. Simply introducing a Windows Server 2008 server into a 2003 environment should be seamless.

Going from Windows Server 2003 to 2008, do you recommend upgrading or re-installing the operating system?
Microsoft supports an upgrade of the OS only – no applications. Most customers however, choose to reinstall with Windows Server.

What are the hardware requirements for this Windows Server 2008?
Minimum is a 1ghz processor, 512mb of RAM, and 20GB of disk space. Details can be found here: http://www.microsoft.com/windowsserver2008/en/us/system-requirements.aspx

Do you have an actual laboratory so that I can practice Windows Server 2008?
You can find the TechNet Virtual Labs here: http://technet.microsoft.com/en-us/virtuallabs/bb512925.aspx

Any difficulties adding a Windows 2008 Server into a 2003 domain? Anything to watch out for?
Adding Windows Server 2008 Member servers to the domain should not be an issue. There are no special things to watch out for, until you start adding Domain controllers. Note that if you add a 2008 member server, and do not extend the schema, some things will be unavailable, like the enhanced DFS capabilities in 2008.

Where can I get a copy of the Windows Server 2008 trial version?
You can obtain the trial version here: http://www.microsoft.com/windowsserver2008/en/us/try-it.aspx. Starting August 20th, you will be able to get R2 in the same location.

Can I do in-place upgrade AD server 2003R2 to Server 2008 without any problem? Also, can I do that same thing with Exchange 2007 server on SRV2003R2?
Microsoft only supports the upgrade of the Operating System from 2003 to 2008. We do not support the upgrade of Windows Server 2003 with applications, so the Exchange 2007 upgrade would not be supported.

Is it possible to use the same imaging deployment method for Windows 2008 physical and virtual machines (in VMware) for consistent builds?
It is possible to use traditional imaging methods for physical and virtual, however in the virtual environment, most customers tend to use template Virtual Hard disks to deploy systems, as it is faster and more flexible than imaging.

What is the difference between GPO and NAP?
Group policy is a part of Active Directory that allows for management of users and computers. NAP, or network access protection provides endpoint health checking for network clients. This integrates with network components to restrict or allow network access. Client NAP configurations can be controlled by GPO, and some GPO settings can be enforced by NAP.

Does NAP work for VPN connections as well?
Yes. It is integrated with Microsoft VPN as well as some partner solutions.

Does XP pro and 2008 Server talk well together? What’s a better path, upgrade your clients to Win7 then servers to 2008? Or vice versa?
XP will work in a 2008 domain environment, but it won’t be able to take advantage of all of the features of 2008. Vista is designed to complement 2008, and Windows 7 works best with 2008 R2 (or 2008). I would recommend deploying Windows Server 2008 for workloads that will gain the most benefit – this will allow you take advantage of it immediately. Then follow with Windows 7 when you are ready.

Do terminal servers have central management to manage users and applications?
There are a number of tools to centrally manage the environment. R2 adds a connection broker component that will publish apps from multiple servers. However, apps still need to be published on each server, and permissions need to be set that way as well. Citrix provides some great centralized mgmt tools that enhance the native tools.

Will 2008 support XP clients?
Yes. 2008 will support XP for many things including Terminal Services, with RDP 6.1 client, NAP, with XP Sp3, Group policy preferences and many other features. Windows Vista and Windows 7 however, are able to take advantage of more features.

I have two Windows 2008 servers that are going to be setup as a cluster for Exchange 2007. Is there a document for setting up the “heartbeat” connection between the two servers?
There are many documents on technet that will help. When you build the cluster, the validation wizard will check the configuration of the heartbeat network to make sure its configured appropriately. Typically, a 2 node cluster will use a cross-over cable, although a non-routed VLAN on a switch also works. Some docs:

Step-by-step guide for basic 2-node cluster: http://technet.microsoft.com/en-us/library/cc731844(WS.10).aspx
Validating an Exchange 2007 Cluster: http://technet.microsoft.com/en-us/library/bb676379.aspx

Is Server 2008 with Exchange supported on VMware?
Exchange Server 2007 SP1 on Windows 2008 is supported – see here for details: http://www.windowsservercatalog.com/svvp.aspx?svvppage=svvp.htm

Is it possible to run a 2008 DC with 2003 DCs without any sort of hacks or work-arounds?
Yes – it is possible. You’ll need to extend the AD Schema and install a 2008 member server, then promote it to a DC. There are some documents here: https://blogs.msdn.com/canberrapfe/archive/2009/04/08/adding-a-2008-domain-controller-to-your-2003-forest.aspx

Regarding the NAP, once a client is quarantined, is there a policy or rule that the admin must create to get the client healthy? Meaning, is it automatic or does the client sit there until someone checks the quarantined clients and fixes the issues?
NAP can be configured to auto-remediate certain things – turning firewall on, turning on autoupdate, etc. For AV, or patches, users can be directed to a web page with simple instructions or links to update the client.

Has load balancing improved with 2008 and TS?
It has been made simpler. Many customers found NLB to be complicated for what was needed on Terminal Services. TS on 2008 uses DNS round robin for initial connection with the TS Farm, then load balancing across nodes is handled by using RDP session load balancing.

How many CALs are included in the bundle of Windows Server 2008?
There are different bundles with 5, 10, or 25 CALS. http://www.microsoft.com/windowsserver2008/en/us/pricing.aspx

How many machines can run on a single user MS Windows Server 2008, because we want to move to VMware soon.
Microsoft supports up to 192 VMs on Windows Server 2008, and 384 on Windows Server 2008 R2. Typically numbers will not be anywhere near this, as other system resources will bottleneck. Details can be found here: http://www.microsoft.com/windowsserver2008/en/us/hyperv-faq.aspx#HyperVWindowsServer2008Specific

Is MS Windows Server 2008 VMware built-in?
Microsoft’s virtualization solution, Hyper-V, is built in to Windows Server 2008 and R2.

How would Hyper-V handle the VMware over committing resources, for example, is ESX server only have 8GB RAM but it can assign 16GB RAM to the VMs because it holds the memory and only releases it when it is required. The main reason for Exchange on a ESX box is not a good idea.
Hyper-V does not support over-commit of memory resources. To assign 8gb of RAM to a VM, you must have 8gb available. This improves performance and security.

What happens when a file which has been transferred/shared to a branch using Branch Cache is opened in the main office? Will the branch be informed about this and vice versa?
When clients use branch cache, each file is referenced by a hash. When a client tries to retrieve a file from the central office, it checks the hash of the file, then compares it to what is in the local cache. If the file has changed, then the hash would have changed, and the client would retrieve the updated version. The branch is not informed if the central copy is opened, only if it is changed, through the hash mechanism.

What is the maximum supported DFS server in 2008? In 2003 I think it is less than 70GB and that was not enough for me.
The File Replication Service in Windows Server 2003 had trouble with replication when data sizes got too big. Windows Server 2008 uses DFS-R (Distributed File System Replication) for replication – this uses an algorithm call Remote Differential Compression, which compresses files, and replicates only changes. This makes replication more efficient, an able to support large volumes of data. The limits that existed in 2003 for data size are either removed, or raised greatly.

What is the standard vs. reduced footprint for Windows 2008?
Processor requirements for Server Core and full Windows Server 2008 are the same. Minimum memory recommendations of 512mb are also the same. While the system requirements on Microsoft.com don’t list separate requirements for Server Core, it typically requires less disk space than a full installation. Additionally, Server Core has fewer roles to install (only 9), fewer services running, and has no GUI.

Are there any plans to integrate snapshot technology within Hyper-V?
Hyper-V already supports snapshots at two levels. First, it supports snapshots of the Virtual Machine itself, through use of memory copies and differential disks. The other snapshot capability is a snapshot backup, performed by the host Hyper-V system, using Volume Shadowcopy Services to back up the running VMs.

When will Hyper-V R2 be released?
Windows Server 2008 R2 and Hyper-V R2 released to manufacturing on July 22nd. General Availability will be in October. Volume license customers should have access to the code on August 19th. More details are available here: http://blogs.technet.com/windowsserver/archive/2009/07/22/when-to-expect-windows-server-2008-r2-rtm.aspx

Can everRun protect a workload that is physical on one side and virtual on the other?
everRun does not install INTO a Windows system, so it isn’t able to protect a ‘physical’ system in this sense. Many of our customers choose to keep some of their applications isolated to a physical server with no other applications or VMs on that host while protecting them with everRun. This is done by creating a single Windows environment within the everRun environment. Although the capability is there to create multiple, a single is the desired approach.

How does everRun handle data stored on NAS?
everRun can use any product data that resides on any type of storage. everRun sees the storage repository as a disk volume and can mirror between any two.

How many licenses for the operating system do I need for this solution? Do I need two licenses for the application (i.e. Exchange) as well?
Typically two licenses of Windows are required, however the Enterprise edition provides benefits when running in virtual environments. Please check with Microsoft on this and with your application vendors as all vendors have different licensing terms for redundant/high availability systems.

How well does everRun work with dissimilar hardware (i.e. at the DR site using older servers)?
There are some requirements for similar server components. If two supported servers are utilized and one happens to have a slower processor, the application may run at the slower speed, depending on the level of protection chosen within everRun.

Does everRun replicate all server data including application data like SQL databases?
Yes. The entire operating environment and all disks, including the OS, application, and application data are mirrored.

Is everRun effective for small companies? For example, an Exchange environment for less than 200 users?
Absolutely. Many of our customers are smaller to mid-sized businesses who require an availability solution that is simple, effective, and doesn’t require SAN storage or dedicated IT staff to manage.

Does everRun support MS Small Business Server?
Yes. Our everRun solution will work with any version of Windows Server, 64-bit or 32-bit. We work for small scale solutions all the way up to enterprises.

Will everRun support Exchange 2010 DAG location geographically?
We are still researching Exchange 2010 capabilities and how they can best be supported by everRun. At this time we are not yet clear on how DAG will or can be supported.

How are system upgrades handled in the everRun environment?
A single upgrade is performed on the single exposed Windows environment. Both of the redundant systems will be updated automatically by everRun. everRun also offers mechanisms to reduce the risk and associated downtime of system upgrades.

How does the actual SQL server app run in the everRun environment?
Exactly the same as it does in a non-everRun environment. everRun sits below the Windows environment therefore there are no application changes required.

The everRun software sounds great, but it requires two physical servers. Any hope of moving forward to do the same work within a VMware or Hyper-V environment?
Today everRun supports virtualized environments running on Citrix XenServer. We announced a joint development agreement with Microsoft back in early 2009 to provide everRun Fault Tolerance within a future version of Windows/Hyper-V.

How is everRun migrated with Windows 2008 hypervisor?
everRun will support a future Windows/Hyper-V release as part of the joint development effort between Microsoft and Marathon.

What system resources are used by everRun?
A small (varies a bit by the application that is running) bit of CPU and memory overhead is consumed by everRun.
 

Show Discussion / Comments (1)
Webinar  Availability  Clustering  Clusters  Continuous Availability  EverRun  EverRun VM  Exchange 2007  Fault Tolerance  High Availability  Marathon  Virtualization  Webcast  Availability  Clustering  Clusters  Continuous Availability  EverRun  EverRun VM  Exchange 2007  Fault Tolerance  High Availability  Marathon  Virtualization  Webcast  Webinar  Availability  Clustering  Clusters  Fault Tolerance  High Availability  Virtualization  Webcast  Availability  Clustering  Clusters  Fault Tolerance  High Availability  Virtualization  Webcast 

| More



Tuesday, June 23rd, 2009 - 11:05 am EDT

Citrix and Marathon Demo at SAP - Part II

Posted by: Brian Mullins

Bhumik Patel of Citrix has posted Part II of the Citrix and Marathon demo at SAP on his blog. Part I of Bhumik’s blog series looked at specific details on Citrix Delivery Center and the Disaster Recovery demonstration for SAP NetWeaver.

Part II covers different high availability solutions also demonstrated at SAP. In addition to this blog series, a Reference Architecture document provides all the technical details about Citrix and Marathon solutions implemented for SAP. When looking for an HA solution, various factors such as application criticality and business impact must be considered before choosing a particular solution for an application. A more detailed report on determining availability requirements can be found here.

The following video from Citrix features the Marathon everRun VM Level 3 High Availability solution demonstrated at SAP Co-Innovation Labs in Palo Alto.


 

 

Show Discussion / Comments (0)
XenServer  Access Virtualization  Availability  Citrix  Continuous Availability  EverRun VM  Fault Tolerance  High Availability  XenServer HA  Access Virtualization  Availability  Citrix  Continuous Availability  EverRun VM  Fault Tolerance  High Availability  XenServer HA  Access Virtualization  Availability  Fault Tolerance  High Availability  Access Virtualization  Availability  Fault Tolerance  High Availability 

| More



Monday, November 24th, 2008 - 3:11 pm EST

UNDERSTANDING DIALABLE AVAILABILITY

Posted by: Brian Mullins


As many of you know, one of the key components of everRun VM is the ability to dial up or dial down the level of availability needed to protect business-critical applications. With buzz surrounding the release of Citrix’ XenServer 5, we have been approached with questions like “what should I use to protect my low-priority applications” and “how do I know when something should or shouldn’t be protected with the lockstep option?” To help explain the three levels of availability and when they would be used, we’ve put together these tips:

LEVEL 1: BASIC FAILOVER WITH XENSERVER HA
The first level of availability, basic failover and recovery, is appropriate for applications where recovery is not absolutely critical, and where manual intervention, while not desirable, is acceptable. These may include infrastructure applications or dev and test systems.
XenServer HA provides:

  • Basic failover to another host within the same Xen pool, with resource calculation to determine whether adequate resources are available within the pool to handle a defined number of simultaneous host failures (XenServer HA does not check the health of available devices, such as network and storage)
  • Monitoring of health of the hosts within a pool (Network and storage health are not monitored)
  • No storage or data protection – using this level requires a shared-storage configuration

LEVEL 2: COMPONENT-LEVEL FAULT TOLERANCE WITH everRun VM
For applications with business-critical roles, everRun VM provides component-level fault tolerance: the ability to withstand the loss of an individual network or storage component without interruption or downtime.
The attributes of Level-2 availability include:

  • Automated setup and fault management: policies handle system, network and disk I/O failures without IT intervention
  • Assured recovery of virtual machines
  • Zero downtime due to I/O failures and zero data loss
  • Synchronous data mirroring between hosts; no need for shared storage
  • Continuous active validation of all components on production and standby system to ensure complete redundancy at all times for recovery in the event of a failure
  • Comprehensive availability including system, network, and data availability, all in one integrated solution

LEVEL 3: SYSTEM-LEVEL FAULT TOLERANCE WITH everRun VM AND LOCKSTEP OPTION
For the most mission-critical systems, Marathon everRun VM with Lockstep Option provides system-level fault tolerance, with continuous availability in the face of component or system-wide failures. Level 3 will be available in 2009 and offers protection for systems that cannot experience any downtime and must maintain transaction state at all costs. everRun VM with Lockstep Option offers all of the benefits of everRun VM (Level 2), together with:

  • Zero downtime even for complete host failures
  • Application state maintained during failures
  • Memory state maintained during failures

For more information on the different levels of availability please visit here.

Show Discussion / Comments (0)
Availability  Citrix  Continuous Availability  Downtime  EverRun  EverRun VM  Fault Management  Fault Tolerance  Marathon  Virtual Machine  XenServer  XenServer HA  Citrix  Continuous Availability  Downtime  EverRun  EverRun VM  Fault Management  Fault Tolerance  Marathon  Virtual Machine  XenServer  XenServer HA  Availability  Downtime  Fault Management  Fault Tolerance  Virtual Machine  Downtime  Fault Management  Fault Tolerance  Virtual Machine 

| More



Tuesday, November 18th, 2008 - 3:46 pm EST

Protecting XenApp with everRun – Citrix Summit Demo

Posted by: Brian Mullins

Citrix Summit is a major event for Citrix partners to learn the best new technology products for application delivery infrastructure solutions. The event was a few weeks ago, and it is worth noting that in the keynote presentation, delivered by Mark Templeton, President and CEO, and Peter Blum, Senior Systems Engineering Manager, they demonstrated Marathon’s everRun VM Level 3 protecting XenApp. What the audience saw was how everRun provided continuous availability for XenApp – even when they unplugged one of the servers.

Did anyone have a chance to see this demo live? What did you think?

Show Discussion / Comments (2)
Availability  Citrix  Continuous Availability  Events  EverRun  EverRun VM  Marathon  Partners  Citrix  Continuous Availability  Events  EverRun  EverRun VM  Marathon  Partners  Availability  Events  Partners  Events  Partners 

| More



Monday, October 27th, 2008 - 6:46 am EDT

The Importance of Maintaining Microsoft Exchange High Availability

Posted by: Brian Mullins

For most organizations, email is single-handedly the most important tool for accomplishing business objectives. Without access to email, companies are at an immediate disadvantage in today’s “I want it now” marketplace. For example, let’s look at the impact email downtime has on productivity: Assuming that your employees are 25% less productive when email is unavailable, and their annual salary is $60,000, then every hour of downtime for an organization of 500 people results in more than $7,200 in lost employee productivity. Can your organization bare a $7,200/hour loss? In today’s economy? Probably Definitely not.

Avoiding the aforementioned consequence is an option, but in order to do so you need to guarantee continuous availability for your organizations email server. According to Paul Rubens at ServerWatch, 2007 forecasts from Gartner revealed that Microsoft Exchange 2007 will own 70% of the email market share by 2010. Now, whether Microsoft will actually return those results, it’s still too early to tell. However, as more and more companies rely on Exchange servers to run business functions, all potential causes of unplanned downtime need to be identified and eliminated.

Over the next month, we will be providing you with some recommendations on how to improve Exchange high availability through planned and unplanned downtime – starting with a webinar on November 11 titled “Virtualizing Exchange – The Cold, Hard Numbers on Why Citrix XenServer and everRun VM is the Best Platform.” For this webinar, Jerry Melnick, Marathon CTO, and Matt Fairbanks, VP of Product Marketing for Citrix Virtualization and Management Division, will team up to discuss how the latest server virtualization technologies keep users continuously connected to Microsoft Exchange servers in the easiest and most effective manner. We encourage you to register online for the webinar if you haven’t already.

Is there anything in particular related to protecting your Exchange severs you would like us to address in the next few weeks? Leave us a comment below and we will be sure to put it on our radar.

Show Discussion / Comments (0)
Availability  Citrix  Continuous Availability  Downtime  EverRun  EverRun VM  Exchange  High Availability  Marathon  Virtualization  Webinar  XenServer  Citrix  Continuous Availability  Downtime  EverRun  EverRun VM  Exchange  High Availability  Marathon  Virtualization  Webinar  XenServer  Availability  Downtime  Exchange  High Availability  Virtualization  Webinar  Downtime  Exchange  High Availability  Virtualization  Webinar 

| More



Tuesday, August 14th, 2007 - 1:44 pm EDT

Continuous Availability

Posted by: admin

Continuous availability virtually guarantees a computing system is operational in the event of any disruption. The concerns for continuous availability focus on two things, the recovery of applications, data and data transactions prior to the moment of disruption, and 24x7 system availability regardless of the planned or unplanned downtime event.

Show Discussion / Comments (1)
Continuous Availability  Glossary  Glossary  Glossary  Glossary 

| More