Virtual TapeServer 6.04.05 for NonStop Servers Supplemental Installation Guide

22 | Enabling and Configuring Data Replication
• SSH must be configured on all VTS servers if you want to secure data when copying data
to remote locations (for Instant DR). Also, it must be configured on all VTS servers
involved in AutoCopy operations. SSH must be configured for Protocol 2 RSA or DSA
encryption using Public Key Identification. Public Key Identification requires that the
sender’s Public Key be installed in the specific authorized_keys file on the receiver VTS
system.
• It is very important that SSH communications flow though network connections from one
VTS system to another. A single gigabit connection is used to handle the SSH data
transfer and other communications between VTS systems. To prevent congestion, because
of the high volume of traffic that can flow over a connection used for Instant DR or
Autocopy, it is recommended that a completely separate gigabit subnet be used to connect
VTS systems. Network speeds of less than a gigabit are not recommended. The ProLiant
servers do not support speeds of greater than one gigabit.
• For AutoCopy, the source and target servers must have the same software version
installed.
After completing the procedures in this chapter, refer to the Virtual TapeServer Configuration
Guide for instructions on using the Data Replication feature to import and export virtual
tapes.
Overview of Instant DR
Instant DR enables you to create and maintain identical copies of backup data on VTS disk
storage at one or more locations. Virtual tapes are transmitted from one vault to another. The
Instant DR jobs indicate the pools or virtual tapes to be transmitted. When a job is initiated, a
copy of the virtual tape is transmitted over the network link. Be aware that the virtual tapes
duplicated on a remote vault consume additional disk space, which is the same amount as the
original virtual tape.
VTS servers cannot “see” each others’ pools and virtual tapes until the Instant DR jobs run.
The pools and virtual tapes in the primary operation page look identical if all virtual tapes are
copied. If selected virtual tapes are copied using the Instant DR job, the virtual tape and pool
lists are different. Automatic Event Management Service (EMS) mounting chooses from pools
as it would in day-to-day operations because the virtual tapes will be created in the new vault.
If an encrypted virtual tape is stored on an Instant DR server and the Instant DR server
attempts to perform an operation on the tape, Data Encryption must be enabled and the key
server that was used to encrypt the tape must be configured on the Instant DR server. If not,
the tape operation will fail and an error message is displayed on the Instant DR server
indicating that the operation failed. Refer to the Virtual TapeServer Configuration Guide for
information about Data Encryption and an explanation of the possible failures.
In general, Instant DR should be used if files do not change much from day to day. Data is
transmitted in batches, one or more times per day, and only data differences are sent.
Bandwidth is consumed when the data transmission is scheduled according to policy, usually
during off-peak hours. Instant DR is supported across multiple sites, from one to many
servers based on the configuration.
Instant DR performs well in environments where the backup data does not significantly
change on a daily basis. Synchronizing transaction files, which can change constantly, is not
necessary a good use of Instant DR. Poor performance may result when synchronizing
transaction files because the process by which Instant DR computes file differences can take