vSphere

Another way to fix your non compliant host profile

Duncan Epping · Mar 20, 2015 ·

I found out there is another way to fix your non compliant host profile problems with vSphere 6.0 when you have SAS drives which are detected as shared storage while they are not. This method is a bit more complicated though and there is a command line script that you will need to use: /bin/sharedStorageHostProfile.sh. It works as follows:

Run the following to dump all your local details in a folder on your first host
```
/bin/sharedStorageHostProfile.sh local /folder/youcreated1/
```
Run the following to dump all your local details in a folder for your second host, you can do this on your first host if you have SSH enabled
```
/bin/sharedStorageHostProfile.sh remote /folder/youcreated2/ <name or ip of remote host>
```
Copy the outcome of the second host to folder where the outcome of your first host is stored. You will need to copy the file “remote-shared-profile.txt”.

Now you can compare the outcomes by running:

/bin/sharedStorageHostProfile.sh compare /folder/youcreated1/

After comparing you can run the configuration as follows:

/bin/sharedStorageHostProfile.sh configure /folder/youcreated1/

Now the disks which are listed as cluster wide resources but are not shared between the hosts will be configured as non-shared resources. If you want to check what will be changed before running the command you can simply do a “more” of the file the info is stored in:
```
more esxcli-sharing-reconfiguration-commands.txt
```
```
esxcli storage core device setconfig -d naa.600508b1001c2ee9a6446e708105054b --shared-clusterwide=false
```
```
esxcli storage core device setconfig -d naa.600508b1001c3ea7838c0436dbe6d7a2 --shared-clusterwide=false
```

You may wonder by now if there isn’t an easier way, well yes there is. You can do all of the above by running the following simple command. I preferred to go over the steps so at least you know what is happening.

/bin/sharedStorageHostProfile.sh automatic <name-or-ip-of-remote-host>

After you have done this (first method or second method) you can now create your host profile of your first host. Although the other methods I described in the post of yesterday are a bit simpler, I figured I would share this as well as you never know when it may come in handy!

Get your download engines running, vSphere 6.0 is here!

Duncan Epping · Mar 12, 2015 ·

Yes the day is finally there, vSphere 6.0 / SRM / VSAN (and more) finally available. So where do you find it? Well that is simple… here:

Have fun!

All Flash VSAN – One versus multiple disk groups

Duncan Epping · Mar 11, 2015 ·

A while ago I wrote this article on the topic of “one versus multiple disk groups“. The summary was that you can start with a single disk group, but that from a failure domain perspective having multiple disk groups is definitely preferred. Also from a performance stance there could be a benefit.

So the question now is, what about all-flash VSAN? First of all, same rules apply: 5 disk groups max, each disk group 1 SDD for caching and 7 devices for capacity. There is something extra to consider though. It isn’t something I was aware off until I read the excellent Design and Sizing Guide by Cormac. It states the following:

In version 6.0 of Virtual SAN, if the flash device used for the caching layer in all-flash configurations is less than 600GB, then 100% of the flash device is used for cache. However, if the flash cache device is larger than 600GB, the only 600GB of the device is used for caching. This is a per-disk group basis.

Now for the majority of environments this won’t really be an issue as they typically don’t hit the above limit, but it is good to know when doing your design/sizing exercise. The recommendation of 10% cache to capacity ratio still stands, and this is used capacity before FTT. If you have a requirement for a total of 100TB, then with FTT=1 that is roughly 50TB of usable capacity. When it comes to flash this means you will need a total of max 5TB flash. That is 5TB of flash in total, with 10 hosts that would be 500GB per host and that is below the limit. But with 5 hosts that would be 1TB per host which is above the 600GB mark and would result in 400GB per host being unused?

Well not entirely, although the write buffer has a max size of 600GB, note that the remainder of the capacity is used by the SSD for endurance, so it will cycle through those cells… and that is also mainly what you are sizing for when it comes to the write buffer. That 10% is mainly around endurance. So you have a couple of options, you can have multiple disk groups to use the full write buffer capability if you feel you need that, or you can trust on VSAN and the flash “internals” to do what they need to do… I have customers doing both, and I have never heard a customer “complain” about the all-flash write-buffer limit… 600GB is a lot to fill up.

vVols primer

Duncan Epping · Mar 9, 2015 ·

I was digging through my blog for a link to a vVols primer article and I realized I never wrote one. I did an article which described what Virtual Volumes (VVol) is in 2012 but that is it. I am certain that Virtual Volumes is a feature that will be heavily used with vSphere 6.0 and beyond, so it was time to write a primer. What is vVols about? What will they bring to the table?

First and foremost, vVols was developed to make your life (vSphere admin) and that of the storage administrator easier. This is done by providing a framework that enables the vSphere administrator to assign policies to virtual machines or virtual disks. In these policies capabilities of the storage array can be defined. These capabilities can be things like snapshotting, deduplication, raid-level, thin / thick provisioning etc. What is offered to the vSphere administrator is up to the Storage administrator, and of course up to what the storage system can offer to begin with. When a virtual machine is deployed and a policy is assigned then the storage system will enable certain functionality of the array based on what was specified in the policy. So no longer a need to assign capabilities to a LUN which holds many VMs, but rather a per VM or even per VMDK level control. So how does this work? Well lets take a look at an architectural diagram first.

The diagram shows a couple of components which are important in the VVol architecture. Lets list them out:

Protocol Endpoints aka PE
Virtual Datastore and a Storage Container
Vendor Provider / VASA
Policies
vVols

Lets take a look at all of these three in the above order. Protocol Endpoints, what are they?

Protocol Endpoints are literally the access point to your storage system. All IO to vVols is proxied through a Protocol Endpoint and you can have 1 or more of these per storage system, if your storage system supports having multiple of course. (Implementations of different vendors will vary.) PEs are compatible with different protocols (FC, FCoE, iSCSI, NFS) and if you ask me that whole discussion with vVols will come to an end. You could see a Protocol Endpoint as a “mount point” or a device, and yes they will count towards your maximum number of devices per host (256). (Virtual Volumes it self won’t count towards that!)

Next up is the Storage Container. This is the place where you store your virtual machines, or better said where your vVols end up. The Storage Container is a storage system logical construct and is represented within vSphere as a “virtual datastore”. You need 1 per storage system, but you can have many when desired. To this Storage Container you can apply capabilities. So if you like your virtual volumes to be able to use array based snapshots then the storage administrator will need to assign that capability to the storage container. Note that a storage administrator can grow a storage container without even informing you. A storage container isn’t formatted with VMFS or anything like that, so you don’t need to increase the volume in order to use the space.

But how does vSphere know which container is capable of doing what? In order to discover a storage container and its capabilities we need to be able to talk to the storage system first. This is done through the vSphere APIs for Storage Awareness. You simply point vSphere to the Vendor Provider and the vendor provider will report to vSphere what’s available, this includes both the storage containers as well as the capabilities they possess. Note that a single Vendor Provider can be managing multiple storage systems which in its turn can have multiple storage containers with many capabilities. These vendor providers can also come in different flavours, for some storage systems it is part of their software but for others it will come as a virtual appliance that sits on top of vSphere.

Now that vSphere knows which systems there are, what containers are available with which capabilities you can start creating policies. These policies can be a combination of capabilities and will ultimately be assigned to virtual machines or virtual disks even. You can imagine that in some cases you would like Quality of Service enabled to ensure performance for a VM while in other cases it isn’t as relevant but you need to have a snapshot every hour. All of this is enabled through these policies. No longer will you be maintaining that spreadsheet with all your LUNs and which data service were enabled and what not, no you simply assign a policy. (Yes, a proper naming scheme will be helpful when defining policies.) When requirements change for a VM you don’t move the VM around, no you change the policy and the storage system will do what is required in order to make the VM (and its disks) compliant again with the policy. Not the VM really, but the vVols.

The great thing about vVols is the fact that you know have a granular control over your workloads. Some storage systems will even allow you to assign IO profiles to your VM to ensure optimal performance. Also, when you delete a VM the vVols will be deleted and the space will automatically be reclaimed by the storage system, no more fiddling with vmkfstools. Another great thing about virtual volumes is that even when you delete something within your VM this space can also be reclaimed by the storage system. When your storage system supports T10 UNMAP that is.

That is in short how vVols work and what they bring. You as the vSphere administrator create policies and assign those to VMs, while the storage administrator manages capacity and capabilities. Easy right?!

vSphere HA respecting VM-Host should rules?

Duncan Epping · Mar 5, 2015 ·

A long time ago I authored this white paper around stretched clusters. During out testing the one thing where we felt HA was lacking was the fact that it would not respect VM-Host should rules. So if you had these configured in a cluster and a host would fail then VMs could be restarted on ANY given host in the cluster. The first time that DRS would then run it would move the VMs back to where they belong according to the configured VM-Host should rules.

I guess one of the reasons for this was the fact that originally the affinity and anti-affinity rules were designed to be DRS rules. Over time I guess we realized that these are not DRS rules but rather Cluster rules. Based on the findings we did when authoring the white paper we filed a bunch of feature requests and one of them just made vSphere 6.0. As of vSphere 6.0 it is possible to have vSphere HA respecting VM-Host should rules through the use of an advanced setting called “das.respectVmHostSoftAffinityRules”.

When “das.respectVmHostSoftAffinityRules” is configured then vSphere HA will try to respect the rule when it can. So if there are any hosts in the cluster which belong to the same VM-Host group then HA will restart the respective VM on that host. Of course as this is a “should rule” HA has the ability to ignore the rule when needed. You can imagine that there could be a scenario where none of the hosts in the VM-Host should rule is available, in that case HA will restart the VM on any other host in the cluster. Useful? Yes, I think so!