Why would you want more than one Persistent Chat pool? We can scale a single pool to 4 active servers each with 20,000 users, to support 80,000 concurrent PChat users – enough for a great many organizations. In many cases, a single central PChat pool makes a lot of sense. With good use of PChat categories, different groups of users can be separated if needed, and administration (such as creating new rooms) easily delegated.
However, this single-pool model doesn’t fit all. Sometimes different regions or countries host their own Lync infrastructure in a shared topology and each will need (or want) their own Persistent Chat pool.
Generally, this works fine but there’s a problem – the dreaded “Your chat room access may be limited due to an outage” message. You may have seen it before if you’ve broken something, but you will also see it if any PChat pool defined in the topology is down.
Your local PChat pool may be up, users may be able to get to their chat rooms, but this can still cause a lot of helpdesk calls. It also looks very similar at a glance to the “Limited functionality” warning, which can impact users’ perception of how reliable Lync is.
There are some practical things you can do to help mitigate this however:
- Agree patching / outage windows for Persistent Chat pools, to avoid users’ typical working hours (in all regions!)
- Care and planning are needed when adding a Persistent Chat pool. Ensure at least one server for the new pools is ready to be installed and configured as quickly as possible, and perform this out of hours.
- Educate users about the message, and what it really means – it’s warning of an outage, but it may not be an outage on their pool!
- Consider limiting the number of users enabled for Persistent Chat – if only 10% of users need it, they’re the only ones who should be enabled. Others won’t see the “outage” warning if they’re not enabled for PChat in the first place.
- Consider limiting the number of PChat pools in the organization. While you can collocate PChat on a Standard Edition server, this only makes sense in small environments. Don’t let the failure of a single server for 100 users cause an outage warning for 100,000+ users!
Hopefully some better logic around this warning will come in future versions of the Lync (or Skype for Business) client. In the meantime, think carefully about whether you want multiple PChat pools and if you do, what you need to do to avoid the dreaded “outage” message!