h1. How long will be down time when upgrading

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Upgrades differ in complexity and in manipulations doe.
Accordingly differs a duration of downtime.
Possible cases:

h2. Minor upgrade

This is upgrade during which only Smartswitch version is upgraded, and possibly several packages are updated too.
For example, when moving from version 6.5 to version 6.6.
A sequence of manipulations done:

  * delete old Smartswitch package
  * install new Smartswitch package
  * upgrade of several other packages
  * config database upgrade
  * CDR database upgrade

h2. Major upgrade

This is upgrade, in which OS version and all packages is upgraded.
For example, moving from version 6.6 to version 7.10.
A sequence of manipulations done:

  * upgrade FreeBSD kernel
  * check that new kernel doesn't have issues with server hardware during several days (we advise 1 week), includes monitoring for:
  - hangs or freezes
  - sudden reboots
  - issues in networking and disk subsystems
  This step is essential, because after full OS upgrade it's impossible to revert it back in case of issues.
  In case if some issues are detected on this stage we can suspend upgrade and revert back old FreeBSD kernel.
  And think about some other way of upgrading to make less harm to your customers (for example moving to other server).
  * upgrade FreeBSD applications
  * delete all old packages
  * install all new packages
  * config database upgrade
  * CDR database upgrade

h2. Manipulations and downtime.

For duration of each step and possible side effects see table below.

|*manipulation*|*duration*|*VoIP services working*|*side effects*|
|FreeBSD kernel upgrade|during system reboot - up to 10 minutes|no|Possible issues with launching new kernel, after which we'll need someone on the data-center to assist us or IP-KVM attached|
|FreeBSD applications upgrade|during system reboot - up to 10 minutes|no|Possible issues with launching new kernel, after which we'll need someone on the data-center to assist us or IP-KVM attached|
|delete all old packages|up to 10 minutes|no||
|install all new packages|up to 10 minutes|no||
|delete old Smartswitch package|up to 1 minute|no||
|install new Smartswitch package|up to 1 minute|no||
|upgrade several packages|up to 5 minutes|no||
|config database upgrade|up to 5 minutes when difference between version is 1 (for example, upgrade from 6.4 to 6.5)|no||
|CDR database upgrade|Duration depends on database size and on difference between versions - from several minutes to several days.|yes|This procedure doesn't affect configuring and using the system, however blocks CDR storing. Therefore, report generation doesn't work. All CDRs are accumulated in temporary database and will be handled automatically when procedure finishes. Balances are updated too.|

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