ssd – Page 3

VSAN Flash/MD capacity reporting

04.29.2014 by William Lam // Leave a Comment

One of the capabilities that is available with VSAN when creating a VM Storage Policy is the ability to specify the amount of to Flash to reserve for a Virtual Machine object as a read cache. For Virtual Machines that require high levels of performance, you can assign this policy to the Virtual machine and VSAN will ensure a percentage of the Flash capacity is provided to your workload.

A couple weeks back I was asked whether it was possible to report on the total amount of Flash capacity available to a VSAN Cluster including what has been reserved and in use. I thought that this was a great idea as users would probably want to be able see their utilization over time and ensure they do not over provision their Flash capacity.

For those of you who have used RVC, this information is somewhat available today using the vsan.disks_stats command. The only problem is that this information is only provided at a per device level for each ESXi host and not in an aggregate view for the entire VSAN Cluster.

Leveraging the work I had done earlier with exploring the VSAN API and looking at the VSAN component count, I was able to extract the necessary information that I was looking for to provide an aggregate view. To demonstrate this functionality, I have created two sample scripts: vSphere SDK for Perl script called vsanFlashAndMDCapacity.pl and PowerCLI script called vsanFlashAndMDCapacity.ps1

Disclaimer: These scripts are provided for informational and educational purposes only. It should be thoroughly tested before attempting to use in a production environment.

Both scripts work exactly the same way, you just need to connect it to a vCenter Server that has at least one VSAN Cluster. The script will automatically search for all VSAN enabled vSphere Cluster and provide the following information:

Total SSD Capacity
Total SSD Reserved Capacity
Total SSD Used Capacity
Total MD Capacity
Total MD Reserved Capacity
Total MD Used Capacity

Here is an example screenshot for the vSphere SDK for Perl script:

Here is an example screenshot for the PowerCLI script:

One question I had myself while looking at the results was regarding the "Used" property and what it meant. I think this is best explained with an example after learning about the details from engineering.

Lets say there are 2 VSAN objects:

Object1: Configured size: 100GB, space reservation 10%, actual data written 5GB.
Object2: Configured size: 100GB, space reservation 10%, actual data written 15GB.

This would mean:

Object1:
Configured/Provisioned: 100GB
Reserved: 10GB
Physical Used: 5GB
Used: 10GB

Object2:
Configured/Provisioned: 100GB
Reserved: 10GB
Physical Used: 15GB
Used: 15GB

The "Used" property is then calculated as the MAX(Physical Used, Reserved). I have also shared this information with engineering, perhaps they may consider adding this information to RVC 🙂 If you think this is something you would like to see in RVC, please leave a comment.

Exploring VSAN APIs Part 2 – Query available SSDs

03.05.2014 by William Lam // Leave a Comment

When enabling VSAN, users have the option to specify how the disks (SSD/HDD) will be added to VSAN either automatically (recommended) or manually claimed by the end user.

If you decide to manually claim your disks on each ESXi host within the VSAN cluster, then you will probably need to figure out which disks are SSD and HDD for you to create your VSAN disk groups. If you have used the vSphere Web Client to perform this operation, you will notice there is a toggle for displaying "eligible" disks for VSAN which can also be obtained programmatically using the vSphere API.

On each ESXi host, there is a vsanSystem manager that provides various methods for disk management and the one that we are interested in is called QueryDisksForVsan(). To demonstrate this functionality, I have created the following sample vSphere SDK for Perl script called vsanQueryDisksForUse.pl. The script will query each ESXi host in a vSphere Cluster and return a list of disks which specifies if they are eligible for use with VSAN and whether the disk is an SSD or not.

Disclaimer: These scripts are provided for informational and educational purposes only. It should be thoroughly tested before attempting to use in a production environment.

To check for the list of available SSD/HDD, run the following command:

./vsanQueryDisksForUse.pl --server vcenter55-1 --username root --cluster VSAN-Cluster

Using this information, you can then use the AddDisks_Task() method to create your own VSAN Disk Groups on each ESXi host. As you can see, it is a couple more steps if you opted for manual mode and I would recommend letting the vSphere platform automatically take care of this for you.

How to quickly setup and test VMware VSAN (Virtual SAN) using Nested ESXi

09.02.2013 by William Lam // 48 Comments

Last week at VMworld 2013, VMware announced the release of vSphere 5.5 which includes a variety of exciting new features. One of the most anticipated feature introduced in this release is VMware Virtual SAN (VSAN) which will be available initially as a public beta. One question that I heard repeatedly throughout the VMworld conference was whether it would be possible to test VSAN in a nested ESXi environment? The answer is absolutely! This is a great way to learn about VSAN and how works from a functional perspective before procuring the necessary hardware.

Disclaimer: Running VSAN in a nested ESXi environment is not officially supported nor is it a replacement for actual testing on actual physical hardware.

Before getting started, I would highly recommend you check out the following resources from my good friend Cormac Hogan which includes a detailed VSAN walk through as well what looks to be an awesome series of articles on how VSAN works:

Requirements:

Environment running either vSphere 5.1 or 5.5 and access to the vSphere Web Client.

Configuration:

Nested ESXi VM configured with the minimal resources:

2 vCPU
5GB Memory (ESXi 5.5 now requires a minimum of 4GB vs 2GB as with previous releases but VSAN requires minimum of 5 with recommended 6)
2GB Disk for ESXi 5.5 installation
4GB Disk for an "Emulated" SSD
8GB Disk for HDD

Easy Method:

Instead of having you go through the process of building a Nested ESXi VM with all the prerequisites that includes steps from here and here. I have pre-built a VSAN Nested ESXi VM template (217Kb) that you can just download and import into your environment and being the installation process.

Download either:

and connect to your vCenter Server 5.1 or 5.5 using the vSphere Web Client and import the OVF into your environment (do not use the vSphere C# Client as the import does not persist VHV configuration). Once you have imported the VM, you can then mount the ESXi 5.5 ISO and begin the installation. All three VMDKs have been thin provisioned and you can change the capacity during deployment.

Slightly Harder Method:

If you wish to build the Nested ESXi VM yourself, then you can follow these instructions:

Step 1 - Create a new VM and when you get to the compatibility screen, select either "ESXi 5.1 or greater" or "ESXi 5.5 or greater" depending on the version of vSphere you are running

Step 2 - For the GuestOS select "Other" and "Other (64-bit)"

Step 3 - We will need to customize the following virtual hardware configuration:

Change vCPU to 2
Click on CPU drop down and enable "Expose hardware assisted virtualization to the guest OS"
Change Memory to 4GB
Change the initial VMDK to 2GB or whatever value you wish to use for ESXi installation
Add second VMDK with 4GB or whatever value you wish to use for "emulated" SSD
Add third VMDK with 8GB of whatever value you wish to use for the HDD
Click on the VM Options tab at the top and select the "Advanced" drop down box. We will need to add the following entry scsi0:1.virtualSSD = 1 For more details please refer to this article

Step 4 - Click okay to provision the VM and once it has been deployed you will need to re-configure the guestOS to "VMware ESXi 5.x" using the vSphere C# Client for vSphere 5.1 or vSphere Web Client for vSphere 5.5. At this point, you will have the same VM image as in the Easy Method and you are now ready to install ESXi 5.5

When you install ESXi 5.5, you should see the following three disks as shown in the screenshot below, ensure you install ESXi on the 2GB disk:

Prior to enabling VSAN on the particular vSphere Cluster, make sure you enable the new VSAN traffic type on one of your VMkernel interfaces for each of your ESXi hosts, this is required for VSAN communication.

If all the prerequisites have been met, you can now easily enable VSAN by simply checking the VSAN box when editing the vSphere Cluster. In just a few minutes you should see diskgroups automatically created (assuming you selected Automatic mode) consuming both the emulated SSD and HDD and the creation of the vsanDatastore which will be available on all ESXi hosts within that vSphere Cluster.

You can also use the same method for emulating an SSD running in a Nested ESXi to functional test the new VMware Flash Read Cache (vFRC) feature.