Active-active clustering is a data resiliency architecture in which client workloads are distributed across two or more nodes in a cluster to keep your data safe and available in the event of an unexpected component failure.
The key difference between active-passive and active-active clustering architectures is performance. Active-passive clusters have client machines connect to the main server, which handles the full workload, while a backup server remains on standby, only activating in the event of a failure.
Active-active clustering is where client machines connect to a load balancer that distributes their workloads across multiple active servers. Active-active clusters give you access to the resources of all your servers during normal operation. In an active-passive cluster, the backup server only sees action during failover.
Common benefits of active-active clusters include:
- High availability of mission-critical apps across data centers, campuses, and metros
- Load balancing across a cluster of servers
- Data redundancy and resiliency (maintain uptime even when one site fails)
1. Pure Storage Active-Active Clustering Setup
- Connect the Arrays
- Create a Stretched POD
- Create a Volume
- Connect Hosts
Purity ActiveCluster uses the same simple and easy storage management model as the rest of FlashArray. To enable ActiveCluster, PureStorage added one new command. It takes only four short steps to setup: Connect the arrays, create a stretched pod, create a volume, and connect the hosts.
2. Connect The Arrays
This section describes how to Connect the Arrays.
1. Go to PureStorage CLI.
2. The following command:
a. Purearray connect –type sync-replication.
Or
1. From the GUI on one FlashArray go to first get a connection key (doesnt matter which array):
2. Click on the hamburger and click “Get Connection Key”
3. Click Copy:
4. Now go to the other array: Repeat the steps above except this time you chose “Connect Array” and enter in the connection key and management address of the array you got the key from and choose “Sync Replication”.
3. Create A Stretched POD
What the HECK is POD? Well, a pod is a namespace, but also a replication group. A pod is first created on a FlashArray, then a second FlashArray is added to it. This is called “stretching a pod”. When a pod is first stretched the initial synchronization of the data starts. When everything is in sync, the volumes are now available on both sides. They can be read from or written to on either array at the same time.
1. Go to the CLI and Type:
a. >purepod create pod1
b. >purepod add –array vMSC- pod01
Or
1. Within the GUI Go to the Pods tab and create a new one and name it something that makes sense:
a. Go to the Storage section, choose Pods and then click the Plus sign
2. At this point add any pre-existing volumes you would like to add to the pod. This is called a volume “move”. The volume is not literally moved, nor is any data copied. The volume is simply moved into the pod namespace. So if my pod is named “codypod” and my volume is currently called “codyvolume”, when the volume is moved into the pod, it will be called “codypod::codyvolume”.
This process is of course non-disruptive to any host I/O to that volume.
4. Create a Volume
1. From the CLI: Type: >purevol create –size 1T pod::vMsc-vol01
Or
2. See above in step 3 the volume is created when copying the volume into the POD
5. Connect Hosts
1. From the CLI: >purehost connect -vol vMSC-pod01::vMSC-vol01
Or
This process is of course non-disruptive to any host I/O to that volume.
When you have finished adding any volumes, you can now stretch the pod to the second FlashArray. 2. From the GUI:
There are a few other option:
1. Use cloud mediator or deploy and internal one. The default behavior is for the FlashArrays to use the cloud mediator. This is the preferred option in general (it ensures it is on a third site for instance). But if you want to deploy an internal mediator, we do offer a vApp.
2. Set an array as preferred for a host. If hosts only have access to the volume through one FlashArray, there is no need for this (called non-uniform configuration). If hosts in both sides have storage access to a volume through both FlashArrays, you might want to set a preferred array. When you set a preferred array for a host, Purity automatically tells the host that its paths are optimized or not optimized. The preferred array paths will be marked optimized and therefore a host will only use those paths. If you do not set this, and there is a latency difference across sites, reads and writes might go to the remote FlashArray instead of the local one, which will add unnecessary latency. I will go more into this in another blog post.
Note: Once a pod is created, you can control the pod and volumes from either FlashArray. If you create a snapshot, that snapshot is created on both sides. If you have snapshots before putting a volume in a pod, then you put the volume in, those snapshots will be copied over too.
If you create a new volume in a stretched pod, it is immediately available in both sides.
So ActiveCluster is not just an active-active clustering solution, it can also be a very simple means to move a volume and its snapshots over to a different array, Put a volume in a pod, stretch it, let it sync, then unstretch it.
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