Tag Archives: AHV

Openstack + Nutanix : Nova and Cinder integration

Now that we have setup an allinone deployment of the Acropolis OVM, configured networking, and an image registry. It’s time to look at the steps required to launch virtual machine (VM) instances and setup appropriate storage.  The first steps to take are to provide the necessary network access rules for the VM’s if they don’t already exist. The easiest way to do this is to create rules to ensure SSH (port 22) access from any address range and to make the VMs pingable.

Compute > Access & Security > Security Groups

Compute > Access & Security > Security Groups

Compute > Access-Security > Security Groups

Compute > Access & Security > Security Groups

Next create an SSH key-pair that can be assigned to your instances and subsequently control VM remote login access to holders of the appropriate private key. I will show how this is used later in the post, when we launch an instance. First, select the Key Pairs tab in the Access & Security frame and save the resulting PEM file to be used when accessing your VMs.


Create a named key-pair (for example fedora-kp) for the set of instances you will create.

As an example, I am going to create a single volume using the Cinder service, in order to show we can attach this to a running VM. In this instance, Cinder gets redirected to the Acropolis Volume API and the subsequent volume gets attached to the instance as an iSCSI block device.


Next step will be to spin up a number of VM instances, I have given a generic instance prefix for the name, and I am choosing to boot a Fedora 23 Cloud image. You can see the Flavour Details in the side panel in the screenshot below – Note the root disk size is big enough to accommodate the base image.


I also need to specify the SSH key-pair I am using and the Network on which the instances get launched. See below :



At this point I can go ahead and launch my instances. We can see the 10 instances chosen all get created below, along with the assigned IP addresses from the already defined network, the instance flavour, and the named key-pair ….


So now, if we were to take a look at the Nutanix cluster backend via Prism, we can see those VM instances created on the cluster and how they are spread across the hypervisor hosts. That’s all down to Acropolis management and placement.


We can dig a little deeper into the Acropolis functionality and show how each of the steps taken by the Acropolis REST API calls have built and deployed the VMs on the backend. Here’s the list of VMs that were created as defined in the http://<CVM-IP>:2030 page.


And we can see the breakdown of the individual task steps and how long each one took and how long they might have queued for, and if they were ultimately successful and so on. The key take away from all this is that the speed of creation of the VM instances is largely down to the Acropolis management interfaces consumed by the REST API calls.


Let’s take one of those VMs and add some volumes to it, let’s add a data and a log volume to fedvm-10. First of all we need to create the iSCSI volumes



Then we can attach the volumes to the VM instance ….


We now have the two volumes attached to the VM ….


The two volumes should show up as virtual disks under /dev in the VM itself. We can verify this by logging into the VM directly using the private key I created earlier as part of the key-pair assigned to this series of instances.

# ssh -i ./fedora-kp.pem fedora@
Last login: Thu Apr 7 21:28:21 2016 from
[fedora@fedvm-10 ~]$ 

[fedora@fedvm-10 ~]$ sudo fdisk -l
Disk /dev/sda: 3 GiB, 3221225472 bytes, 6291456 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes
Disklabel type: dos
Disk identifier: 0x6e3892a8

Device Boot Start End Sectors Size Id Type
/dev/sda1 * 2048 6291455 6289408 3G 83 Linux

Disk /dev/sdb: 10 GiB, 10737418240 bytes, 20971520 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

Disk /dev/sdc: 50 GiB, 53687091200 bytes, 104857600 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 4096 bytes / 4096 bytes

So from here, we can format the newly assigned disks and mount them as needed.

That’s it for this post, hopefully this series of posts has gone a little way to clarify how a Nutanix cluster can be used to scale out an Openstack deployment to form a highly available on-premise cloud. The deployment of which is radically simplified by using Nutanix as the Compute, Volume, Image and Network backend.

In future posts I intend to look at deploying an upstream Openstack controller, have a play around with snapshots within Openstack and their use as images. Also, some additional troubleshooting perhaps. Let me know what you find useful.

Sharded MongoDB config on Nutanix (1) : Deployment

So far I have posted on MongoDB deployments either as standalone or as part of a replica set. This is fine when you can size your VM memory to hold the entire database working set. However, if your VM’s RAM will not accommodate the working set in memory, you will need to shard to aggregate RAM from multiple replica sets and form a MongoDB cluster.

Having already discussed using clones of gold image VMs to create members for a replica set, then the most basic of MongoDB clusters requires at least two replica sets. On top of which we need a number of MongoDB “infrastructure” VMs that make MongoDB cluster operation possible. These entail a minimum of three (3) Configuration Databases (mongod –configsvr) per cluster and around one (1) Query Router (mongos) for every two shards. Here is the layout of a cluster deployment on my lab system:


In the above lab deployment, for availability considerations, I avoid co-locating any primary replica VM on the same physical host, and likewise any of the Query Router or ConfigDB VMs. One thing to bear in mind is that sharding is done on a per collection basis. Simply put, the idea behind sharding is that you split the collections across the replica sets and then by connecting to a mongos process you are routed to the appropriate shard holding the part of the collection that can serve your query. The following commands show the syntax to create one of the three required configdb’s (ran on three separate VMs, and need to be started first), and a Query Router, or mongos process (where we add the IP addresses of each configdb server VM) :

Config DB Servers – each ran as:
mongod --configsvr --dbpath /data/configdb --port 27019

Query Router - ran as:
mongos --configdb,,

- the above IP addresses in mongos command line are the addresses of each config DB.

This brings up an issue if you are not cloning replica VMs from “blank” gold VMs. By cloning a new replica set from a current working replica set, ie: so that you essentially have each replica set holding a full copy of all your databases and their collections. Then when you come to add such a replica set as a shard, you generate the error condition shown below.

Here’s the example of what can happen when you attempt to shard and your new replica set (rs02)  is simply cloned off a current running replica set (rs01):

mongos> sh.addShard("rs02/")
 "ok" : 0,
 "errmsg" : "can't add shard rs02/ because a local database 'ycsb' 
exists in another rs01:rs01/,,"

This is the successful workflow adding both shards (the primary of each replica set) via the mongos router VM:

$ mongo --host localhost --port 27017
MongoDB shell version: 3.0.3
connecting to: localhost:27017/test
mongos> sh.addShard("rs01/")
{ "shardAdded" : "rs01", "ok" : 1 }
mongos> sh.addShard("rs02/")
{ "shardAdded" : "rs02", "ok" : 1 }

We next need to enable sharding on the database and subsequently shard on the collection we want to distribute across the replica sets available. The choice of shard key is crucial to future MongoDB cluster performance. Issues such as read and write scaling, cardinality etc are covered here. For my test cluster I am using the _id field for demonstration purposes.

mongos> sh.enableSharding("ycsb")
{ "ok" : 1 }

mongos> sh.shardCollection("ycsb.usertable", { "_id": 1})
{ "collectionsharded" : "ycsb.usertable", "ok" : 1 }

The balancer process will run for the period of time needed to migrate data between the available shards. This can take anywhere from a number of hours to a number of days depending on the size of the collection, the number of shards, the current workload etc. Once complete however, this results in the following sharding status output. Notice  the “chunks” of the usertable collection held in the ycsb database are now shared across both shards (522 chunks in each shard) :

 mongos> sh.status()
--- Sharding Status ---
 sharding version: {
 "_id" : 1,
 "minCompatibleVersion" : 5,
 "currentVersion" : 6,
 "clusterId" : ObjectId("55f96e6c5dfc4a5c6490bea3")
 { "_id" : "rs01", "host" : "rs01/,," }
 { "_id" : "rs02", "host" : "rs02/,," }
 Currently enabled: yes
 Currently running: no
 Failed balancer rounds in last 5 attempts: 0
 Migration Results for the last 24 hours:
 No recent migrations
 { "_id" : "admin", "partitioned" : false, "primary" : "config" }
 { "_id" : "enron_mail", "partitioned" : false, "primary" : "rs01" }
 { "_id" : "mydocs", "partitioned" : false, "primary" : "rs01" }
 { "_id" : "sbtest", "partitioned" : false, "primary" : "rs01" }
 { "_id" : "ycsb", "partitioned" : true, "primary" : "rs01" }
 shard key: { "_id" : 1 }
 rs01 522
 rs02 522
 too many chunks to print, use verbose if you want to force print
 { "_id" : "test", "partitioned" : false, "primary" : "rs02" }

Additional Links: