Tag Archives: PVS

Do we still need to tuning storage/SMB for PVS 7.* servers?

Recently I spent lots of time to check how to improve PVS 7.* server performance to reduce the vDisk loading time.
And it seems on the internet there are lots of articles talking about tuning storage (both storage server and PVS server) to enable ‘oplock’.
But I found that almost all these articles are based on PVS 5.* and windows 2003/2008.
So do we still need to tuning storage/SMB for PVS servers?

Citrix has a good article to answer this quetion:
https://www.citrix.com/blogs/2018/09/05/pvs-internals-4-vdisk-stores-and-smb3/

Just check the summary part:

Using file share storage for vDisks is still a valid and recommended approach, if sufficient capacity and high availability is in place. Especially in environments without redundant resp. highly available file services, I’d rather recommend local replicated vDisk stores instead of using just a single file server that definitely constitutes a single point of failure. And no one needs to invest in expensive file clustering solutions if its only purpose would be to provide file shares for vDisk storage.
Caching will help to significantly reduce the load on file servers or filers. Unlike earlier versions, there are no tuning requirements, neither for the PVS servers, nor for file servers. The defaults are perfectly fine. Sizing guidelines for PVS server memory (RAM) from past articles still apply.
Consider the caching behavior of the SMB redirector. There is a chance that shutting down all target devices connected to a particular vDisk will also remove the vDisk’s cache entries and the cache will need to be warmed up again on the next boot.
Leverage the latest SMB protocol if possible, at the time or writing this article it’s SMB 3.1.1. Not only Windows file servers support SMB3, but also modern filers such as NetApp, and even my home lab Synology is able to support SMB3.
Leasing is key for caching, so don’t use SMB 1.x or 2.0 (in fact you shouldn’t even enable the optional SMB 1.x feature on your PVS servers), and forget about any ‘oplock tuning’. Anything from SMB 2.1 onwards is fine with its defaults, but SMB 3.x brings added features that might be beneficial for you, such as ODX when taking copies of a vDisk file.

So it seems the only thing we need to do is to disable SMB 1.0 on PVS server. How to do it? Here is the link:

https://support.microsoft.com/en-us/help/2696547/detect-enable-disable-smbv1-smbv2-smbv3-in-windows-and-windows-server

Understanding Citrix Performance Issues

Bottleneck: provisioning services. Customers note there is excessive Network I/O and CPU utilization.
Bottleneck: vDisk fragmentation or server virtual instances. Customer notes there is excessive page file utilization and disk I/O.
Bottleneck: delays mounting new vDisks. Check for excessive Network and Disk I/O on delivery controllers.
Bottleneck: delivery controllers. Check for excessive historical CPU utilization.
Bottleneck: slow application enumeration. Check for excessive disk and network I/O on the data collectors.
Bottleneck: slow session creation noted within the director console: Check for historical CPU and Memoyr consumption, consider adding VCPU and memory when/where needed.
Bottleneck: higher than expected user logons. Check for high CPU and/or network utilization (not historical but may trend at random intervals). Add processing or new delivery controller if necessary to handle the expected loads.
Bottleneck: issues with local host cache (LHC). Disk and Page File I/O in excess can cause unanticipated issues with LHC. Alert and adjust when/where needed.
Bottleneck: Processor intensive apps. Check questionable servers for larger disk I/O and page file utilization. Consider adding more VCPU’s and/or memory to offset the demand on disk and page file.
Bottleneck: vDisk and/or Provisioning Services. Check for higher than normal CPU and/or Memory consumption as a deficiency will slow down the loading of vDisks and caching via Provisioning Services (PVS).
Bottleneck: Web interface authentication. Consider adding more memory and looking at network utilization trends. It may be necessary to either add more memory or to add an additional WI to your GSLB URL.
Bottleneck: slow PXE and vDisk. Check for memory and/or network utilization and consider addresssing depending on noted trends.
Bottleneck: target device latency. Check CPU and network I/O for spikes and/or trending issues.

Provisioning Services (PVS) and Daylight-Saving Time

With daylight-saving time beginning at week’s end (March 8 at 2am), we got some issues that can occur with PVS delivered desktops and XenApp servers.

Some of the issues that occur as a result of the time change are:

Time not showing correctly in the Desktop or XenApp server,
Desktop failure to register with DDCs,
User inability to log on due to domain trust relationship issues caused by the VM/Domain time difference.

The Fix:

Open up your PVS delivered image(s) in read/write mode after the time change has occurred on Sunday.
Run “w32tm /resync /nowait” at the command prompt.
Set the image(s) back to read only, following your normal image preparation procedures.

Remember, you must reboot all PVS delivered desktops and servers after you make the above changes to ensure they receive the updated version.

Being proactive will help ensure a smooth Monday morning for all of your users!

More information on this issue can be viewed here: http://support.citrix.com/article/CTX200058

Citrix PVS server Dual IP issue in multiple DHCP servers with a split scope environment

Usually, when deploy PVS servers, we only use 1 DHCP scope. But for some large environment, we have to use multiple DHCP servers with a split scope if we can’t use Windows Server 2012.

Then it’s more likely to get the dual IP issue:

1. When VDI start, first, it contacted DHCP server to get the 1st IP address, then use this IP address to connect to PVS server to start to download the image and startthe VDI.
2. And when windows is up, windows DHCP client will request an IP address from DHCP server. In multiple DHCP environment, it may request IP address from a different DHCP server and got a different IP address..

Then we got below problem:
1. VDIs may have two IP address.
2. We run out IP address. You will find that lot’s IP address are marked as ‘bad addresses’
3. DNS record issue. Because some VDIs have two IP addresses, VDIs registered the wrong IP address to DNS server.

We spent lots of times with Citrix, and Citrix can’t provide a solution for this issue. They only suggest to use PVS server in single DHCP scope environment.

But finally, we found a solution to fix this issue by ourselves.

This issue was caused by that when windows is up, Citrix PVS Device Service will inject the IP address it got during PXEboot process into system. And if Citrix PVS Device Service starts before DHCP client service, then VDI will get 1 IP address. But if DHCP client start first, Citrix will still inject the IP address, and then VDI will get two IP addresses.

There are two ways to fix this issue.

1. Disable DHCP client in VDI. This option is not good, but it works. But please be aware that after you disable DHCP client service, the VDI may not be able to get DNS server from DHCP servers. Because Citrix only inject IP address/Netmask/Gateway information to windows.

2. Make “Citrix PVS Device Service” as a dependency service of DHCP client servers to make sure that DHCP service starts after Citrix inject the IP address.

Dual to Citrix can’t fix this issue, this is the only solution we found to fix this issue.
But if you are able to use windows server 2012, then go for windows server 2012 DHCP cluster maybe another choice.