Dell Unity: Write performance issue in robocopy when using CA (User Correctable)

When CA (Continuous Availability) is enabled, Write response is longer than 100ms.

Examples of Occurrence Conditions
 The following conditions caused the problem
 -Continuous Availability (CA) is enabled in the SMB share option.
 -Write a Roaming User Profiles or home directory with robocopy.
 -When robocopy is executed by multiple users (300 users) at the same time and the load is heavy, the problem is noticeable.
  If the load is increased further, the response may deteriorate further and SMB Usage Thareads may reach the upper limit.

Check the following items in the UPA.
In addition to Write, you will notice that the response time is poor.

UPA
File >> SMB2 >> OP >> Call Response Time(ms)
SMB2_Close
SMB2_Write
SMB2_Create
SMB2_Setinfo

 

When CA (Continuous Availability) is enabled, folder redirection, offline files, roaming user profiles, or home directories are written directly to disk without caching, resulting in poor performance in the event of a large number of writes.

Disable CA (Continuous Availability)

Unisphere operation
 File >> SMB Shares
 Select the target share name.
 Go to "Advanced" from the Share Properties screen.
 Uncheck "Continuous Availability" from SMB properties.

Dell Unity: NAS Capabilities:
https://www.delltechnologies.com/en-us/collaterals/unauth/white-papers/products/storage/h15572-dell-emc-unity-nas-capabilities.pdf
Read the following sections to see if you need to enable this CA (Continuous Availability).
7.1.4 Continuous Availability
7.1.1 Sync Writes Enabled

MS document:
https://docs.microsoft.com/en-us/windows-server/failover-clustering/sofs-overview
Folder Redirection, Offline Files, Roaming User Profiles, or Home Directories generate a large number of writes that must be immediately written to disk (without buffering) when using continuously available file shares, reducing performance as compared to general purpose file shares.

https://techcommunity.microsoft.com/t5/storage-at-microsoft/controlling-write-through-behaviors-in-smb/bc-p/1083417#M677
We also enable the CA share flag on regular file server cluster nodes but admins often disable it for performance reasons, the same way they might avoid SoFS for compatibility reasons. Remember when I wrote the Shakespearean prose to scale out or not to scale out? CA is not designed for copying files but for handing IOs on a file opened then being modified forever because it’s a virtual machine or database.