You can upgrade from Couchbase Server 1.8.1 to Couchbase Server 2.0 using either the online or offline upgrade method. See Upgrading to Couchbase Server 1.8 for more information.
Use Online Upgrades for Couchbase Server 1.8.1 to Couchbase Server 2.0
We recommend online upgrade method for 1.8.1 to 2.0. The process is quicker and can take place while your cluster and application are up and running. When you upgrade from Couchbase Server 1.8.1 to Couchbase Server 2.0, the data files are updated to use the new Couchstore data format instead of the SQLite format used in 1.8.1 and earlier. This increases the upgrade time, and requires additional disk space to support the migration.
Be aware that if you perform a scripted online upgrade from 1.8.1 to 2.0 you should have a 10 second delay from adding a 2.0 node to the cluster and rebalancing. If you request rebalance too soon after adding a 2.0 node, the rebalance may fail.
Linux Upgrade Notes for 1.8.1 to 2.0
When you upgrade from Couchbase Server 1.8.x to Couchbase Server 2.0 on Linux, you should be aware of the OpenSSL requirement. OpenSSL is a required component and you will get an error message during upgrade if it is not installed. To install it RedHat-based systems, use yum:
root-shell> yum install openssl098e
On Debian-based systems, use apt-get to install the required OpenSSL package:
shell> sudo apt-get install libssl0.9.8
Windows Upgrade Notes for 1.8.1 to 2.0
If you have configured your Couchbase Server nodes to use hostnames, rather than IP addresses, to identify themselves within the cluster, you must ensure that the IP and hostname configuration is correct both before the upgrade and after upgrading the software. See Section 2.4.1, “Hostnames for Couchbase Server 2.0.1 and Earlier”.
Mac OSX Notes for 1.8.1 to 2.0
There is currently no officially supported upgrade installer for Mac OSX. If you want to migrate to 1.8.1 to 2.0 on OSX, you must make a backup of your data files with cbbackup, install the latest version, then restore your data with cbrestore. For more information, see Section 7.8, “cbbackup Tool” and Section 7.9, “cbrestore Tool”.