High Availability Overview Paper

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1 High Availability Overview Paper March 2001 Please note: The information contained in this document is intended as a guide to implementing high availability systems. Please keep in mind, however, that planning for high availability is a complex undertaking, requiring the consideration of many variables. Therefore, the information provided in this document should be evaluated within context of your existing infrastructure. Documentum Consulting Services has helped many customers plan, implement and test high availability systems in a variety of environments. Please contact them for more information. Page 1 of 9 High Availability Overview Paper 03/20/01

2 DOCUMENT OVERVIEW... 3 BACKUPS VS. HOT STANDBY VS. HIGH AVAILABILITY... 3 BACKUPS... 3 HOT STANDBY... 3 HIGH AVAILABILITY (HA)... 3 FEATURE COMPARISON... 4 GENERAL CONCLUSIONS... 4 WHAT DO YOU NEED TO PROTECT?... 5 STATIC DATA... 5 DYNAMIC DATA... 5 NETWORK TOPOLOGY... 5 DOCUMENTUM SUPPORTED SOLUTIONS... 5 HOT STANDBY... 6 FEATURE DETAILS... 6 SERVER CHECKLIST... 6 STEP 1 - SETUP THE STANDBY SERVER... 6 STEP 2 - PREP THE STANDBY SERVER... 6 STEP 3 - UPDATE THE CONFIGURATION FILES... 7 STEP 4 - SETUP METADATA UPDATES... 7 STEP 5 - SETUP CONTENT UPDATES... 7 STEP 6 - AUTOMATE AND TEST... 7 FAILOVER PROCEDURE... 7 HIGH AVAILABILITY... 8 SOME HA NOTES... 8 HOW DO I PROTECT MY RIGHTSITE?... 8 DATA PROTECTION VS. VAILABILITY... 8 SERVER BALANCING... 8 SERVER CLUSTERING... 8 DISTRIBUTED ENVIRONMENTS... 9 TWO MAJOR PLAYERS... 9 NETWORK STRATEGIES...9 Page 2 of 9 High Availability Overview Paper 03/20/01

3 Document Overview This document highlights the options for creating a High Availability environment for your Docbase. After reading the document you should have an understanding of the different approaches, the pros and cons of each and an idea of the amount of work that would be required. More detailed information may be available for each option. Check out the support website, Documentum Consulting services or your local SE for further information. Backups vs. Hot Standby vs. High Availability Backups What are your options and what do they mean? There are 2 kinds of backups. Backups taken while the Docbase is offline are called 'Cold', those take while the Docbase is online are called 'Hot'. Backups are the most common method of data protection. They have the following features Pros No specialized software or training Low cost Backup-medium can be kept offsite Hot Standby Cons Time consuming Error-prone Difficult recovery (Often not tested enough) Maximum possible data loss is typically about 24 hours A Hot Standby is a 'nearly-current', offline mirror of a Docbase. It is maintained by performing a periodic refresh of an offline/ready system with up-to-date data. If the live Docbase becomes unavailable it is possible to switch to the Hot Standby machine. Pros Easy to setup and maintain No specialized hardware or software Quick recovery time Standby server can be offsite Maximum possible data loss measured in minutes Backups can be run on standby server High Availability (HA) Cons Requires mirror platform Maximum possible data loss measured in minutes In order to implement a 'High Availability' system you need to have ongoing, continuous replication of data with one or more separate systems. Pros Nearly 100% uptime Theoretically no data loss Backups can be performed while system is up Cons Proprietary software required Training required Requires mirror platform Possible proprietary hardware required High cost (in most cases) Page 3 of 9 High Availability Overview Paper 03/20/01

4 Feature Comparison Nightly (Cold) Backups Hot Backups Hot Standby HA Solution Max Data Loss 24hrs. Varies (Probably 1hr) Varies (Probably 5min) Theoretically None Recovery Time (fewer is better) Almost Immediate Hardware Cost $ $ $$ - $$$ $$$ - $$$$ Software Cost 0 - $$ 0 - $$ 0 $$ - $$$ Setup & Maintenance Time Solution Complexity System Availability Configuration Flexibility General Conclusions ❾ Where cost is not an issue, and availability is, a third-party High Availability (HA) Solution is the clear winner ❾ Where uptime and performance are not issues, and users can stand to lose a day s work, standard backups are fine ❾ Hot Standby finds a middle ground between the high cost of HA and poor performance/risk of standard backups Page 4 of 9 High Availability Overview Paper 03/20/01

5 What do you need to protect? Consider what it is you will need to protect in order to implement the level of Availability required. Typically we include Static and Dynamic data however it is important not to disregard the network topology in your planning. Static Data ❾ Documentum Binaries $DM_HOME/ ❾ Documentum Configuration Files $DOCUMENTUM/dba/ ❾ RDBMS Binaries $ORACLE_HOME/ ❾ General OS Binaries and Registry ❾ C:\Winnt, etc. Network Topology Dynamic Data ❾ RDBMS Metadata Tablespaces Control Files Archive Logs ❾ Documentum Content Storage Areas ❾ Documentum Log Areas ❾ OS Authentication Information ❾ Putting all your servers on one, non-redundant, data path negates all your other architecture planning Routers don t have to fail to affect your network Documentum Supported Solutions Documentum econtent sever already provides functionality that can be utilized to provide some degree of High Availability support. ❾ Documentum Server Clusters Provides partial High Availability coverage Provides increased scalability Easy to manage using latest Documentum Administrator client ❾ Redundant Docbrokers ❾ Replication Can provide RW or RO coverage, depending upon setup and specific object Page 5 of 9 High Availability Overview Paper 03/20/01

6 Hot Standby Feature Details It s Fast, It s Free, and You Already Own the Tools! ❾ Requires mirror platform: Similar, but not necessarily identical platforms are usually sufficient, and cost-effective ❾ Standby server can be offsite: Allows for extreme disaster recovery (ex. extended power failure, flood, etc.) ❾ Maximum data loss measured in minutes: Data is as current as the last execution of the update-scripts Provides flexibility in configuration and resource utilization Server Checklist Two Required Same OS Version E4500 Solaris 7 2GB RAM 40GB RAID 5 Same Disk Capacity Network Connectivity Time Synchronization Software (optional) Maintain Minimums for CPU and Memory Sizing E250 Solaris 7 1GB RAM 40GB Disk Ethernet This step-by-step section assumes that the production system is already up and running. Step 1 - Setup the Standby Server ❾ Configure disk paths or mount points to be identical, if possible Really only required for Documentum and RDBMS software and data, not core OS files ❾ Drives / mount points must have same capacity RAID configuration can vary from box to box, but is always a plus ❾ Choose a network-resource for authentication so you don t have to worry about it LDAP, NT Domains, NIS+, etc. Step 2 - Prep the Standby Server ❾ UNIX A cold backup of the Documentum and RDBMS binaries and data is sufficient. Restore these backups onto the standby server in the identical locations. ❾ NT You ll need to first install the RDBMS and Documentum software to sync the registry information. Use the same names and Ids to keep the registry identical. Restore cold backups of Documentum and RDBMS binaries and data over the Documentum/RDBMS installation. Do Not Start the RDBMS or Docbase! Page 6 of 9 High Availability Overview Paper 03/20/01

7 Step 3 - Update the Configuration Files ❾ The following files need to be updated for host-specific information: RDBMS Files: (Oracle examples) tnsnames.ora listener.ora Documentum Files: server.ini dmcl.ini docbroker.ini dm_stop_docbroker Step 4 - Setup Metadata Updates ❾ Leverage RDBMS Capabilities Oracle Example Run Oracle in Archive Log Mode Set the archive destination to a shared directory At each script-iteration, force a log switch Standby DB runs in special continuous recovery mode Standby DB is not open for connections At each iteration, force standby DB to apply archive log Step 5 - Setup Content Updates ❾ Leverage Documentum s Architecture Server never deletes (or overwrites) content, only dmclean and dmfilescan jobs do this You can run a content update anytime after the metadata copy as long as you don t run dmclean or dmfilescan in between! Use the KISS principle rsync is an open-source, cross-platform tool that keeps directory structures completely in sync Only transfers the byte-level differences in files instead of copying each FREE!!! ( Step 6 - Automate and Test ❾ Setup your procedures to run as cron jobs or using the NT Scheduler service Maintain the last successful iteration date, and always use this date for your content-filter You ll need to keep a set of status-flags for the exporter and the loader Example site is running these every 5 minutes (For a maximum 5-minute data loss!) ALWAYS TEST YOUR CONFIGURATION!!! Failover Procedure ❾ Verify configuration files have been changed ❾ Shutdown the database and bring it up in normal mode ❾ Startup Documentum (Docbroker and Docbase) ❾ Have your DNS Administrator re-point the failed server s name to the standby server s IP address OR use the DMCL_Master and/or UNC path options for a centralized dmcl.ini file and simply change that ❾ Have your users log back in! Page 7 of 9 High Availability Overview Paper 03/20/01

8 High Availability Some HA Notes So Many Options, So Little Time! ❾ Educate Yourself! High Availability includes an entirely new vocabulary Vendor feature comparisons Vendor reputation and support options What do you really need? ❾ Shared-Nothing sounds bad, but is it? ❾ Don t forget about failback ❾ SQL Server 2000 Failover Clustering How Do I Protect My RightSite? Data Protection vs. Availability ❾ Data on RightSite and Web Server is fairly static Cold or Hot Backups should suffice Do you need to backup the RightSite and Web Server logs? ❾ Availability and Scalability is extremely important Server Balancing Server Clustering Server Balancing ❾ Multiple RightSite Servers can be statically balanced by providing different users with different URLs OK for small-to-medium size intranet applications May need rebalancing occasionally ❾ Dynamic load balancing has better benefits Allows easy scalability upgrades Need 3rd party software that supports session affinity MS Windows Load Balancing Service (WLBS) is free for NT Server Clustering ❾ May not be necessary if using a Server Balancing solution Most OS vendors have a decent package May require dedicated hardware Examples Windows MSCS HP CampusCluster, MetroCluster, and ContinentalCluster Sun Cluster 2.2 3rd party vendor packages Page 8 of 9 High Availability Overview Paper 03/20/01

9 Distributed Environments Two Major Players No Advanced Degrees Required. ❾ Distributed Content Need to worry about all the content and configuration files covered in previous sections Database is located on one server ❾ Replication Services Need to perform similar tasks to previous sections and cover additional content storage areas Be sure to cover all content storage areas and all database instances Network Strategies ❾ Requirement of updating remote projection information IP Address coverage, DNS update, or server configuration files Page 9 of 9 High Availability Overview Paper 03/20/01

Alfresco 2.1. Backup and High Availability Guide

Alfresco 2.1. Backup and High Availability Guide Copyright (c) 2007 by Alfresco and others. Information in this document is subject to change without notice. No part of this document may be reproduced or transmitted in any form or by any means, electronic