++ availability notes

content/u/products/ungleich-infrastructure-availability/contents.lr

@@ -15,8 +15,68 @@ availbility requirements. In the IT industry, we usually use the
 concept of accepted percentage downtime per year. The follow table
 lists the typical availability categories:
 
+```
 | %      | Accepted downtime / year |
 | 99     | 87h or 3.65 days         |
 | 99.9   | 8.76h                    |
 | 99.99  | 0.876h or 52.55 minutes  |
 | 99.999 | 5.25 minutes             |
+```
+
+## General availability
+
+If not otherwise specified, the **target availability** for every
+service is at minimum 99.9%. This availability is **not guaranteed by
+default**. However we offer **guaranteed availability** for a range of
+our products.
+
+## Guaranteed availability
+
+We can guarantee availability of individual services depending on your
+needs. As every customer need and product is individual, you can
+[ask for an individual offer](/u/contact/) for your services.
+
+## High Availability Methods
+
+To improve the default availability, we offer a variety of
+add-ons. Depending on the booked service, different methods are
+applicable. In this section we describe the general methods we offer.
+
+### Redundant storage
+
+By default all data is replicated 3 times accross our decentralised
+storage system. This protects against disk failures like a traditional
+RAID system does. Note that this does not protect against
+unintentional deletion, for this you require a backup.
+
+### Offsite backup
+
+To allow disaster recovery, we offer [offsite backups](../backup/)
+for most of our services. The data is stored in a physical different
+location so that even physical damage to a data center will allow you
+to restore your data.
+
+### Dedicated Internet uplinks and IP blocks
+
+To protect you against DDoS and impacts on our general infrastructure,
+we offer dedicated Internet uplinks that are reserved for your
+service. This includes a /48 IPv6 address block by default for BGP
+announcement. A /24 IPv4 address block for indidivual BGP announcement
+can be added at an extra service cost.
+
+### Redundant services / High availability (HA)
+
+We realise high availability (HA) using redundant services. These
+services can be placed in the same geographic or different geographic
+data centers. Depending on the service architecture we offer
+Cold-Standby, Hot-Standby or active-active services.
+
+With different geographic locations separate data storage is included
+by default. For services in the same location, an optional separate
+data storage is also available.
+
+### Load Balancing
+
+For services that allow multiple backends, we offer load balancing
+services to distribute the traffic. This can be combined with
+dedicated uplinks per location and indivual IP address blocks.