See also: Migration between EPiServer 4-5-6 is as easy as 1-2-3 (part 2), which covers the actual migrate/upgrade process, along with some additional references for code migration and troubleshooting.

Overview: 

This is really a massive subject which cannot be easily summarised in one blog post. However, there are lots of good sources of information out there which I have tried to collect and structure, and throw in a few comments based on my own experience. Hopefully this might serve as a good starting point for those who are about to begin the upgrade/migration process.

Note: This post applies to EPiServer 4.60 and above. If your site is pre-4.60, I'd recommend that you start from scratch instead :-) It is assumed the reader is familiar with EPiServer Manager, EPiServer Deployment Center and installation/use of the various separate EPiServer versions. This post does not cover areas like filesystem converting, post-migration configuration or code migration (handling breaking changes).

 

EPiServer versions overview

(Final releases only, no Release Candidate versions)

 Release  DLL version  Download / Docs  Installer  Migration tools
 .NET ver  System Req's
 4.60  4.60.0.165  [D/L] [Inst] [Rel] [Tech]  Manager 1.2    1.1, 2.0  [Req]
 4.61  4.61.0.83  [D/L] [Inst] [Rel] [Tech]  Manager 1.3.2    1.1 SP1, 2.0  [Req]
 4.62B 1)  4.62.0.469  [D/L] [Inst] [Rel] [Tech]  Manager 1.3.3

Migration Tool 1.1.0.38 3)

[Documentation]

 1.1 SP1, 2.0  [Req]
 5 R1  5.1.422.4  [D/L] [Inst] [Rel] [Tech] [Brk]  Manager 2.0.18.1    3.0  [Req]
 5 R1 SP1  5.1.422.122  [D/L] [Inst] [Rel] [Tech]  Manager 2.0.19.4    3.0  [Req]
 5 R1 SP2  5.1.422.256  [D/L] [Inst] [Rel] [Tech]  Manager 2.0.19.10    3.0  [Req]
 5 R1 SP3  5.1.422.267  [D/L] [Inst] [Rel] [Tech]  Manager 2.0.19.10    3.0  [Req]
 5 R2 2)  5.2.375.7  [D/L] [Inst] [Rel] [Tech] [Brk]  Deploym.Center

 Migration Tool 1.1.0.38

[Documentation]

 3.5 SP1  [Req]
 5 R2 SP1  5.2.375.133  [D/L] [Inst] [Rel] [Tech]  Deploym.Center    3.5 SP1  [Req]
 5 R2 SP2  5.2.375.236  [D/L] [Inst] [Rel] [Tech]  Deploym.Center    3.5 SP1, 4.0  4)  [Req]
 6  6.0.530.0  [D/L] [Inst] [Rel] [Tech] [Brk]  Deploym.Center    3.5 SP1, 4.0 4)  [Req]

D/L = Download | Inst = Installation instructions | Rel = Release notes | Tech = Technical notes | Brk = Breaking changes | Req = System requirements

 

Upgrade vs Migration

EPiServer-wise, there is a slight difference between the terms "upgrade" and "migration". In general:

However, in both cases it might be necessary to rewrite some code or configuration because of breaking changes in the DLLs or database structure (check the Tech Notes section for each version).

 

The fastest route from EPiServer 4 to 6

Everyone knows that the fastest way to beat Super Mario Bros (Nintendo 1985) is to warp from world 1-2 to 4-1 and then 4-2 to 8-1, kick Bowser's a$$ and have the Princess safely home in time for tea.

Similarily, the fastest way to migrate from EPiServer 4 up to EPiServer 6 is the following sequence:

With any luck, you should be able to skip the CMS 5 R1 versions completely.
If your site is any other version than the above mentioned, you will have to upgrade to the nearest version using the appropriate CMS Manager, Migration Tool or Deployment Center - see above table.

 

General tips

 

See also: Migration between EPiServer 4-5-6 is as easy as 1-2-3 (part 2), which covers the actual migrate/upgrade process, along with some additional references for code migration and troubleshooting.