Double-Take Release NotesVersion 4.4.1.0.1958 for Linux, September 05, 2008© 2008 Double-Take Software, Inc. All rights reserved.This readme file contains last minute release notes about the Double-Take® release that is not included in the user documentation. The user documentation is available on the product CD and in the /usr/share/doc/DT directory after you have installed Double-Take. See Installation Notes for details on how to access the user documentation.
Be sure to check the readme file posted on the product updates download page of the Double-Take Software web site for the latest release notes. The readme file contained in the self-extracting zip file or on the CD may not contain all of the most recent information.
Contents
- Overview
- Installation Notes
- Known Issues
3.1. Installation and configuration
3.2. Replication
3.3. General functionality
3.4. Clients- Contact Information
1. Overview
1.1. This release is an updated release that includes, but may not be limited to, the following features.
1.1.1. Operating system support-Double-Take for Linux now supports Red Hat Enterprise Linux versions 5.0 and 5.1.
1.2. This release is an updated release that supersedes all previous releases. You can safely upgrade to this release from any previous Double-Take for Linux release.
1.1.2. SNMP-Double-Take now provides an SNMP sub-agent that monitors Double-Take and can be managed from an SNMP Management Console.
1.1.3. Compression-To help reduce the amount of bandwidth needed to transmit Double-Take data, compression allows you to compress data prior to transmitting it across the network.
1.1.4. E-mail notification-Messages logged to the event log can be sent as e-mail messages to specific addresses specified.
1.1.5. Support for virtual systems-Double-Take now supports virtual systems.
2. Installation Notes
2.1. The following manuals are available on the product CD and in the /usr/share/doc/DT directory after you have installed Double-Take. To view the manuals, you must have Adobe® Acrobat® Reader® or an equivalent reader such as GGV.
2.1.1. instllnx.pdf-The Getting Started guide contains server requirements, installation and upgrade instructions, an overview of the Double-Take clients, and basic connection information to get you started with Double-Take.
2.1.2. dtuser.pdf-The User's Guide contains a product overview and step-by-step instructions for each Double-Take feature. The manual is also a reference for Double-Take error messages, program settings, and DTCL commands.
2.1.3. evaluationguide.pdf-The Evaluation Guide is a step-by-step process which walks you through installing Double-Take and evaluating the major product features by actually creating and using test data with a Double-Take connection.
3. Known Issues
3.1. Installation and configuration
3.1.1. The .rpm installation packages do not verify that they are being installed on the correct operating system. For example, the .rpm file for Red Hat Enterprise Linux version 5.0 can be installed on a version 4.0 system, even though it will not run on that system. Make sure you are installing the correct .rpm file for your operating system.
3.2. Replication
3.1.2. The Double-Take configuration file /etc/dt/dt.conf is initially blank. To populate it with default values, start and stop the daemon once.
3.1.3. Double-Take does not directly support nested mount points. If you mount one mount point as DTFS, that mounting will not extend the DTFS layer to the nested mount points. You must mount each mount point as DTFS individually, when using a nested mount point configuration.
3.1.4. Red Hat version 4.5 has an issue where the gam_server process uses too much or possibly all of the available CPU. Double-Take may increase the exposure of the gam_server issue, and in return the gam_server issue may decrease Double-Take performance. Additionally, gam_server requires a server reboot when unmounting a replication mount point. Double-Take Software has confirmed an available patch resolves these gam_server issues. If you experience these issues, you should consider applying the patch. For more details, see the Red Hat bug report at https://bugzilla.redhat.com/show_bug.cgi?id=240154.
3.1.5. If you are using Samba, make sure that the location of the lock file (lock dir in samba.conf) is not a location in your Double-Take replication set. If the lock file is replicated to the target, it will become corrupted.
3.2.1. Do not select the root as a replication mount point.
3.3. General functionality
3.2.2. The Management Console will display all mount points capable of supporting replication. Those that have been mounted for replication will be identified as DTFS mount points. Select data from these mount points for replication. If the mount point you want is not labeled as DTFS, you must mount it for replication through the DTSetup utility. Mounting can occur without restarting the daemon.
3.2.3. If you have hard links in your replication set, the verification report will not display the full attributes. This issue may be resolved in a later release.
3.2.4. The access-time file property changes during a mirror and causes replication operations to be generated during a mirror and every time a file is read from or written to. This may have a negative effect on performance. If you turn off access time (noatime option) on both the source and target when the volume is initially mounted, you may increase the performance, especially during mirroring. This issue may be resolved in a future release.
3.2.5. Two replication operations are sent when a file is closed. This may have a negative effect on performance. This issue may be resolved in a future release.
3.3.1. If you uninstall the software while there is an active Double-Take connection, you must reboot the server before reinstalling the software again. This issue may be resolved in a later release.
3.4. Clients
3.3.2. If you specify NoMoveAddresses with the MonitorOption DTCL command, the addresses will still be moved after failover. This issue may be resolved in a later release.
3.3.3. When you schedule start criteria for transmission, you may see the transmission status in an error state at the scheduled start. The transmission will still continue as expected. This may be resolved in a later release.
3.3.4. When you schedule a verification process, it may run a verification report when you save the scheduled verification settings. The scheduled verification will still process as expected. This may be resolved in a later release.
3.3.5. If you are moving or deleting orphan files, keep in mind the following caveats.
3.3.5.1. Long path names will not be removed. This may be resolved in a later release.
3.3.6. Files that were open or being accessed at the time of failover will generate Stale NFS file handle error messages. Remount the NFS share to correct this error.
3.3.5.2. Select a move location outside of the replication set. If you select the location where the files are currently located, the files will be deleted. If you select another location inside the replication set, the files will be moved multiple times and then possibly deleted.
3.3.5.3. The Log Orphaned Files to Target List option on the Connection Manager, Orphans tab is dependent on moving or deleting the orphan files. It does not function on its own.
3.3.7. If you are using Red Hat Enterprise Linux version 4.x, do not export NFS on any subdirectories below where you mounted the DTFS driver, otherwise the source server will stop responding and you will have to reboot it. If you need to export NFS, do it at the parent directory. This is not an issue on Red Hat Enterprise Linux version 5.x. This issue may be resolved in a later release.
3.4.1. If you are monitoring two servers for failover and one of the servers fails, the Failover Control Center display will reflect the countdown of the server that is still connected. Therefore, failover for the first machine will not occur. If you are going to monitor multiple servers for failover, use the Text Client or DTCL. This issue may be resolved in a later release.
3.4.2. If you are using the Failover Control Center, you must have host entries or DNS entries for the servers and the client machine in order to login to a server.
3.4.3. Do not reduce the size of the Text Client window to less than 80x25.
3.4.4. The interactive text client (DTCL -i) may intermittently fail if there is no DNS entry or way for a server to resolve server names.
4. Contact Information
4.1. Product Updates-Check your service agreement to determine which updates and new releases you may be eligible for. These updates can be obtained from the support website at support.doubletake.com.
4.2. Sales-If you need maintenance renewal, an upgrade activation code, or other sales assistance, contact your reseller/distributor or a Double-Take Software sales representative. Double-Take Software contact information is available on the Double-Take Software web site at www.doubletake.com/company/contact-us/.
4.3. Technical Support-Contact the technical support center identified on your service agreement. This is generally the reseller or distributor who you purchased your product from. If you do not have access to this agreement, contact Double-Take Software Technical Support and we can direct you to the correct service provider. To contact Double-Take Software Technical Support, you will need your serial number and activation code. For a complete list of technical support contact information, including phone numbers and e-mail addresses, visit the support page of the Double-Take Software web site at www.doubletake.com/support/.
4.4. Documentation-Please forward any comments or suggestions about Double-Take Software documentation to documentation@doubletake.com.
Double-Take, GeoCluster, Double-Take for Virtual Systems, and NSI are registered trademarks of Double-Take Software, Inc. Balance and Double-Take ShadowCaster are trademarks of Double-Take Software, Inc. Microsoft, Windows, and the Windows logo are trademarks or registered trademarks of Microsoft Corporation in the United States and/or other countries. Linux is a registered trademark of Linus Torvalds. Red Hat is a registered trademark of Red Hat, Inc. in the United States and other countries. All other trademarks are the property of their respective companies.© 2008 Double-Take Software, Inc. All rights reserved.