File upload very slow for File shares v12 for large files.

[mtaimur]

Which service(blob, file, queue, table) does this issue concern?

Azure.Storage.Files.Shares;

Which version of the SDK was used?

v12

Which platform are you using? (ex: .NET Core 2.1)

.net

What problem was encountered?

uploading a large file (>500MB) takes very long complete compare to v11

How can we reproduce the problem in the simplest way?

upload large file

Have you found a mitigation/solution?

tried used the transfer options but get error with it.
TransferOptions = new StorageTransferOptions
{
MaximumConcurrency = 2,
InitialTransferSize = 4 * 1024 * 1024,
MaximumTransferSize = 4 * 1024 * 1024
}