Sentrynet High Availability and Sync solutions for SentryMail.

We are pleased to introduce the HA (high availability) and mailbox sync solutions.

In recent time we have observed failures and data loss on servers due to hardware, software corruptions, viral infections and human errors to mitigate these issues we introducing two options to support.

Mailbox sync :

This solution will sync the mail data between two servers can be in same location or geographically isolated to more protection. Mailbox synchronization utility. It can be used for several different use cases: Two-way synchronization of mailboxes in different servers via secure tunnel , creating backups of mails to a remote server, and convert mailboxes from/to different mailboxes. The syncing is done as perfectly as possible: an IMAP or a POP3 client shouldn't be able to notice any differences between the two mailboxes. Two-way syncing means that it's safe to do any kind of modifications in both sides, and sync will merge the changes without losing any changes done on either side. This is possible because sync can access index logs that keep track of changes. It's of course possible to have conflicts during merging, these are resolved in a safe way. See the sync design document for more information. sync can be run completely standalone. It doesn't require any live mail server processes to be running, except when using user parameter to do a user database lookup from auth process. sync can currently sync only one user at a time. If you want to sync all users, you'll need to get a list of all users and execute sync serially for each one which allows us to set priorities.

Mailbox-sync with HA :

Combined with sync the HA solution offers failover solution. HA ensures continuation of services while sync has all data in place so user has no downtime. As compared to backup solution which results in loss of data due to time gap between backup this is live sync implementation so all data is available on all servers. This enables us to serve all users even in event of complete failure of server. Application: Requisite for sync and HA is new version of sentrymail be installed as we have included all plugins and sync softwares required, if the servers are geographically isolated the connect line should be good enough to manage this data transfers as emails results in huge traffic. First of all, why sync replication instead of block level filesystem replication? - dsync won't replicate filesystem corruption. - A cold restart of replication won't go through all of the data in the disks, but instead quickly finds out what has changed. - Split brain won't result in downtime or losing any data. If both sides did changes, the changes are merged without data loss. - If using more than 2 storages, the users' replicas can be divided among the other storages. So if one storage goes down, the extra load is shared by all the other storages, not just one. This replicator plugin based on notify plugin. It listens for all changes that happen to mailboxes (new mails, flag changes, etc.) Once it sees a change, it sends an asynchronous (username, priority) notification to replication-notify-fifo. The priority can be either high (new mails) or low (everything else).



Minimum of 2 servers having equivalent storage capacities. Processors / ram/ other config can differ doesn’t affect the operation. Cross cable on two different lan cards on each location so mail traffic is not affected by sync. A good bandwidth if using geographically isolated locations.


Sync and HA solution can be implemented with new version of sentrymail. your current Sentrymail will be upgraded free on your requirement of Sync or with HA.