An Architect's vision

Aerospike  is a  flash -optimized  in-memory  open source  NoSQL  database and the name of the company that produces it. http://www.aerospike.com/

Redis   is an in- memory  but persistent on disk database, so it represents a different trade off where very high write and read speed is achieved with the limitation of data sets that can't be larger than   memory . Redis is an open source (BSD licensed), in-memory data structure store, used as database, cache and message broker. It supports data structures such as strings, hashes, lists, sets, sorted sets with range queries, bitmaps, hyperloglogs and geospatial indexes with radius queries. Redis has built-in replication, Lua scripting, LRU eviction, transactions and different levels of on-disk persistence, and provides high availability via Redis Sentinel and automatic partitioning with Redis Cluster. You can run atomic operations on these types, like appending to a string; incrementing the value in a hash; pushing an element to a list; computing set intersection, union and difference; or getting the member with highest ranking in a sorted set. In order ...

Here's what Site Recovery can do for your business: Simplify your BCDR strategy —Site Recovery makes it easy to handle replication, failover and recovery of multiple business workloads and apps from a single location. Site recovery orchestrates replication and failover but doesn't intercept your application data or have any information about it. Provide flexible replication —Using Site Recovery you can replicate workloads running on Hyper-V virtual machines, VMware virtual machines, and Windows/Linux physical servers. Easy failover and recovery —Site Recovery provides test failovers to support disaster recovery drills without affecting production environments. You can also run planned failovers with a zero-data loss for expected outages, or unplanned failovers with minimal data loss (depending on replication frequency) for unexpected disasters. After failover you can failback to your primary sites. Site Recovery provides recovery plans that can include scripts and Azure a...

Physical isolation  – When possible, Azure prefers at least 300 miles of separation between datacenters in a regional pair, although this is not practical or possible in all geographies. Physical datacenter separation reduces the likelihood of natural disasters, civil unrest, power outages, or physical network outages affecting both regions at once. Isolation is subject to the constraints within the geography (geography size, power/network infrastructure availability, regulations, etc.). Platform-provided replication   - Some services such as Geo-Redundant Storage provide automatic replication to the paired region. Region recovery order  – In the event of a broad outage, recovery of one region is prioritized out of every pair. Applications that are deployed across paired regions are guaranteed to have one of the regions recovered with priority. If an application is deployed across regions that are not paired, recovery may be delayed – in the worst case the chosen ...

Azure operates in multiple geographies around the world. An Azure geography is a defined area of the world that contains at least one Azure Region. An Azure region is an area within a geography containing one or more datacenters. Each Azure region is paired with another region within the same geography (with the exception of Brazil South which is paired with a region outside its geography), together making a regional pair.

Read-access geo-redundant storage (RA-GRS) maximizes availability for your storage account, by providing read-only access to the data in the secondary location, in addition to the replication across two regions provided by GRS. In the event that data becomes unavailable in the primary region, your application can read data from the secondary region. When you enable read-only access to your data in the secondary region, your data is available on a secondary endpoint, in addition to the primary endpoint for your storage account. The secondary endpoint is similar to the primary endpoint, but appends the suffix  –secondary  to the account name. For example, if your primary endpoint for the Blob service is myaccount.blob.core.windows.net , then your secondary endpoint is  myaccount-secondary.blob.core.windows.net . The access keys for your storage account are the same for both the primary and secondary endpoints.

Geo-redundant storage (GRS) replicates your data to a secondary region that is hundreds of miles away from the primary region. If your storage account has GRS enabled, then your data is durable even in the case of a complete regional outage or a disaster in which the primary region is not recoverable. For a storage account with GRS enabled, an update is first committed to the primary region, where it is replicated three times. Then the update is replicated to the secondary region, where it is also replicated three times, across separate fault domains and upgrade domains. Note: With GRS, requests to write data are replicated asynchronously to the secondary region. It is important to note that opting for GRS does not impact latency of requests made against the primary region. However, since asychronous replication involves a delay, in the event of a regional disaster it is possible that changes that have not yet been replicated to the secondary region may be lost if the data cann...

Zone-redundant storage (ZRS) replicates your data across two to three facilities, either within a single region or across two regions, providing higher durability than LRS. If your storage account has ZRS enabled, then your data is durable even in the case of failure at one of the facilities. Note: ZRS is currently available only for block blobs, and is supported only in versions 2014-02-14 and later. Note that once you have created your storage account and selected zone-redundant replication, you cannot convert it to use any other type of replication, or vice versa.

Locally redundant storage (LRS) replicates your data within the region in which you created your storage account. To maximize durability, every request made against data in your storage account is replicated three times. These three replicas each reside in separate fault domains and upgrade domains. A fault domain (FD) is a group of nodes that represent a physical unit of failure and can be considered as nodes belonging to the same physical rack. An upgrade domain (UD) is a group of nodes that are upgraded together during the process of a service upgrade (rollout). The three replicas are spread across UDs and FDs to ensure that data is available even if hardware failure impacts a single rack and when nodes are upgraded during a rollout. A request returns successfully only once it has been written to all three replicas. While geo-redundant storage (GRS) is recommended for most applications, locally redundant storage may be desirable in certain scenarios: LRS is less expensive tha...

There are four types of storage available in Azure Locally redundant storage (LRS) Zone-redundant storage (ZRS) Geo-redundant storage (GRS) Read-access geo-redundant storage (RA-GRS) The following table provides a quick overview of the differences between LRS, ZRS, GRS, and RA-GRS, while subsequent sections address each type of replication in more detail. Replication strategy LRS ZRS GRS RA-GRS Data is replicated across multiple facilities. No Yes Yes Yes Data can be read from the secondary location as well as from the primary location. No No No Yes Number of copies of data maintained on separate nodes. 3 3 6 6