This file contains some important notes on upgrade process.

* Upgrading to LizardFS 2.6.0:

    Direct upgrade is possible from:
    - MooseFS  1.6.27 -- 1.6.27-5
    - LizardFS 1.6.28 -- 2.5.4.3

    When upgrading from LizardFS 2.5.4 or 2.5.4.*
    - Upgrade shadow master servers before the master server; shadow master will always
      refuse to connect to the master server in any newer version.
    - Upgrade the master server before any chunkserver or client.

    When upgrading from LizardFS 2.5.0 or 2.5.2
    - Proceed the same as in case of upgrade to LizardFS 2.5.4.

    When upgrading from other releases:
    - Proceed the same as in case of upgrade to LizardFS 2.5.2.

* Upgrading to LizardFS 2.5.4:

    Direct upgrade is possible from:
    - MooseFS  1.6.27 -- 1.6.27-5
    - LizardFS 1.6.28 -- 2.5.2

    When upgrading from LizardFS 2.5.0 or 2.5.2:
    - Upgrade shadow master servers before the master server; shadow master will always
      refuse to connect to the master server in any newer version.
    - Upgrade the master server before any chunkserver or client.
    - Clients, chunkservers and the master server can be upgraded in any order (all of them
      are compatible with each other), either one by one or all at once.
    - CGI server 2.5.4 is compatible with all versions of the master server (1.6.27 -- 2.5.2),
      so it can be upgraded at any time. Because of a bug in older versions of the CGI server
      it has to be stopped manually before being upgraded (otherwise installation of the newer
      package may fail).

    When upgrading from other releases:
    - Proceed the same as in case of upgrade to LizardFS 2.5.2.

* Upgrading to LizardFS 2.5.2:

    Direct upgrade is possible from:
    - MooseFS  1.6.27 -- 1.6.27-5
    - LizardFS 1.6.28 -- 2.5.0

    When upgrading from LizardFS 2.5.0:
    - Upgrade shadow master servers before the master server; shadow master will always
      refuse to connect to the master server in any newer version.
	- Upgrade the master server
    - Clients, chunkservers and the master server can be upgraded in any order (all of them
      are compatible with each other), either one by one or all at once.

    When upgrading from previous releases:
    - There is no possibility to use shadow masters 2.5.2 before upgrading the master server.
    - Upgrade the master server first, then all the chunkservers and then clients (either all
      at once or one by one).

* Upgrading to LizardFS 2.5.0:

    Direct upgrade is possible from:
    - MooseFS  1.6.27 -- 1.6.27-5
    - LizardFS 1.6.28

    Master server has to be upgraded before any client.
    Chunkservers can be upgraded in any order (before the master server is upgraded or after).
    Shadow master server 2.5.0 is compatible with master server 1.6.27 and newer.

* Upgrading to LizardFS 1.6.28:

    Direct upgrade is possible from:
    - MooseFS 1.6.27 -- 1.6.27-5.

    All the servers and clients are compatible and can be upgraded in any order.
