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That very much depends on your Storage system, number of VMs, is this VDI ? (Windows 7, WIndows 8, Windows 10) when you refer to users logging in.<br />
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Is this impacting performance, and are users experiencing slow login times, e.g. 20 minutes to login
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It's a Citrix XenApp running on an HP P2000. <br />
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Yes, the users are now complaining of slow logons, but generally slow when accessing applications. However, the performance issues only last for about an hour when people are all logging in and opening their various applications. After that, things just settle down.<br />
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CPU and memory don't appear to be stretched at all when you view within the vSphere management console.
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This is to be expected wit storage, (slow non flash storage), when you experience a broadcast storm.<br />
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e.g. logging in, logging off, all reading the same email, virus scanning.<br />
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You may have to considered a flash based solution, or flash cache product.
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Maybe worth looking into Atlantis ILIO...<br />
<a href="http://www.atlantiscomputing.com/products/diskless-vdi/" rel="ugc">http://www.atlantiscomputing.com/products/diskless-vdi/</a>
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vmware recommends to keep disk latency under 30ms (aka at least 30 IOPS per VM)<br />
Expensive vcenter editions manage latency using feature called SIOC, which is essentially reducing storage request queue (both NFS and VMFS) until latency is acceptable. They manage to do that on running ESXi, but if you dont have SIOC in your vcenter you must restart ESXi for such adjustment.<br />
You can find the parameter names e.g. <a href="https://community.netapp.com/fukiw75442/attachments/fukiw75442/fas-and-v-series-storage-systems-discussions/2645/1/NetAppandVMwarevSphereStorageBestPracticesJUL10.pdf" rel="ugc">here</a>
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We are currently looking at an issue with performance within our virtualised estate. We can't see anything obviously wrong with CPU or memory, however we noticed the 'Highest Latency' value on each of the hosts seem high.<br />
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Of the four ESX hosts (VMware 5.1), we can see that the Highest Latency maximum value is 21ms, 275ms, 40ms and 30ms.<br />
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We notice the issues notably in the morning when people are logging on to their various systems. Once they've gone through that more intensive part of the day, things seem to settle down and average latency values are 3ms, 7ms, 4ms and 7ms.<br />
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During these peak times are the above maximum values likely to be causing an issue?
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We are currently looking at an issue with performance within our virtualised estate. We can't see anything obviously wrong with CPU or memory, however we noticed the 'Highest Latency' value on each of the hosts seem high.

Of the four ESX hosts (VMware 5.1), we can see that the Highest Latency maximum value is 21ms, 275ms, 40ms and 30ms.

We notice the issues notably in the morning when people are logging on to their various systems. Once they've gone through that more intensive part of the day, things seem to settle down and average latency values are 3ms, 7ms, 4ms and 7ms.

During these peak times are the above maximum values likely to be causing an issue?

Disk Latency - Performance Issue

VMware, a software company founded in 1998,  was one of the first commercially successful companies to offer x86 virtualization. The storage company EMC purchased VMware in 1994. Dell Technologies acquired EMC in 2016. VMware’s parent company is now Dell Technologies.

VMware has many software products that run on desktops, Microsoft Windows, Linux, and macOS, which allows the virtualizing of the x86 architecture.  Its enterprise software hypervisor for servers, VMware vSphere Hypervisor (ESXi), is a bare-metal hypervisor that runs directly on the server hardware and does not require an additional underlying operating system.

VMware

Virtualization is the act of creating a virtual (rather than actual) version of something, including (but not limited to) a virtual computer hardware platform, operating system (OS), storage device, or computer network resources. Virtualization is usually the creation of a system that executes separate from the underlying hardware resources, or the creation of an entire desktop for systems located elsewhere, similar to thin clients.