web, mail, db, dns, …
High-availability for web applications
High-availability solution for web applications and web service providing, implemented on multiple levels – with server virtualization technologies and clustering that use multiple physical and virtual servers.
With our solution, almost all kinds of services can make use of high availability concept – DNS, mail, web, ftp, web application, database servers etc.
Some legacy applications store data in files on server’s filesystem. Even if you have multiple servers running same application, data in files won’t be replicated magically – you have to use some kind of shared storage, for example NFS.
But, introducing NFS server that is used by multiple application servers also introduces new single point of failure.
We have solution for this problem – highly available shared NFS storage. It is implemented as redundant, HA-aware storage subsystem, kind of “network RAID-1”, that uses Pacemaker clustering software with DRBD and NFS on top.
Highly-available applications that store data in database servers need HA-aware database, too.
High-availability for databases depends on type of high availability and scalability application needs, and depends on type of database that is actually used:
- master – slave configuration
- multiple – master database cluster
Some of databases implicitly have HA options (mainly NoSQL ones), while others need engineered solution to establish required level of high availability. Multi-master solutions tend to have own clustering stack, while master-slave solution often requests engineered DB cluster.
Requests to web applications, web services or HA-aware databases are routed from clients over highly availability directors to multiple backing servers.
HA directors itself are highly-available, i.e. if one of them fails, other will take all service requests.
For maximum reliability, physical servers located in different data centers are linked with VPN connections with dynamic OSPF routing.
All physical and virtual servers, web and networks services are actively monitored. Monitored data is available through web user interface.