User Layer HA

[Andrew Rosenau]

I'm looking at deploying app layering but I'm not sure the best way to make the user layer HA. Our environment is vmware 6 with windows Datacenter licensing, back end storage is a Compellent SAN. What is the recommended approach to make the user layer HA?

[CarlStalhood]

User Layers are VHD files stored on UNC share. VHD files are always open, so DFS Replication won't work. Windows Scale Out File Server can handle VHD files.

[Rob Zylowski]

I don't know any way to get real HA with user layers.  Once the user layer is attached to the desktop if it is disconnected for any reason the user will have to logout/reboot and log on again.  If the user layer were corrupted its likely that whatever technology you use for the storage will not know that so it will take a recovery process to get the user layers back.

 

So backups become critical but backing up user layers is challenging because they are locked by the user.  A backup/recovery strategy will depend on the storage architecture you choose.  I have heard from customers using file server clusters like Scale Out File Server that a VSS backup is working well for them on the file server.  This provides the ability to backup even if users have not logged out.  Also SAN/NAS backups should work as they do the backups underneath the file system using something like NDMP.

 

So backups are important, as is using a clustered file system so that if a node fails the user layer will keep running.

 

I have covered most of this here:

https://www.citrix.com/products/citrix-virtual-apps-and-desktops/resources/understanding-elastic-layering.html

and here

https://www.citrix.com/products/citrix-virtual-apps-and-desktops/resources/app-layering-4x-availability-recovery-guide.html

 

 

Good Luck,

Rob

[Andrew Rosenau]

8 hours ago, Rob Zylowski1709158051 said:

Once the user layer is attached to the desktop if it is disconnected for any reason the user will have to logout/reboot and log on again. 

 

So my primary focus for HA is for zero downtime maintenance of the file servers. (Windows updates, etc) So my thought was to use server 2016/2019 scale out file server on vmware and then use RDM for the user layer disks. But are you saying even if I did this if I rebooted one of the file servers users would lose connection to their user disk and then have to log out and back in to regain connection?

[Rob Zylowski]

User layers are vhd’s mounted by windows desktops from the share. Do you mean you want to make the sofs clustered disks using an rdm?

[Andrew Rosenau]

1 hour ago, Rob Zylowski1709158051 said:

User layers are vhd’s mounted by windows desktops from the share. Do you mean you want to make the sofs clustered disks using an rdm?

 

Yes I'm trying to make the share where the VHD's would be stored highly available. Is there a better way to do this other than sofs and rdm?

[Rob Zylowski]

A clusteted file system is required. There are lots of ways to do that but SOFS is a good one. 

 

[Andrew Rosenau]

Thank you, I think I have a good understanding to start testing this.

[Jeff Riechers]

I use DFS-R with preference to keep users using a particular file server.  Once the user logs off the layer is replicated over to the other server/datacenter.

 

It won't handle immediate failures, but does keep data protected between logins.

[Jarian Gibson]

I've been testing Peer Software using their replication feature. Work well so far in my testing.

[Rob Zylowski]

That's good to know Jarian looks like it does a block level delta file sync somehow which would be perfect for user layers.  Do you know if it requires VSS in the VDAs to work?  Definitely let us know how it goes.

 

Rob