Adding some content from a dev

Author: normesta

articles/storage/common/storage-ref-azcopy-copy.md

@@ -229,7 +229,7 @@ Copy a subset of buckets by using a wildcard symbol (*) in the bucket name from
 
 `--block-blob-tier`    (string)    upload block blob to Azure Storage using this blob tier. (default "None")
 
-`--block-size-mb`    (float)    Use this block size (specified in MiB) when uploading to Azure Storage, and downloading from Azure Storage. The default value is automatically calculated based on file size. Decimal fractions are allowed (For example: 0.25).
+`--block-size-mb`    (float)    Use this block size (specified in MiB) when uploading to Azure Storage, and downloading from Azure Storage. The default value is automatically calculated based on file size. Decimal fractions are allowed (For example: 0.25). When uploading or downloading, the maximum allowed block size is 0.75 * AZCOPY_BUFFER_GB. To learn more, see [Optimize memory use](storage-use-azcopy-optimize.md#optimize-memory-use).
 
 `--cache-control`    (string)    Set the cache-control header. Returned on download.
 

articles/storage/common/storage-ref-azcopy-sync.md

@@ -108,7 +108,7 @@ Note: if include and exclude flags are used together, only files matching the in
 
 ## Options
 
-`--block-size-mb`    (float)    Use this block size (specified in MiB) when uploading to Azure Storage or downloading from Azure Storage. Default is automatically calculated based on file size. Decimal fractions are allowed (For example: 0.25).
+`--block-size-mb`    (float)    Use this block size (specified in MiB) when uploading to Azure Storage or downloading from Azure Storage. Default is automatically calculated based on file size. Decimal fractions are allowed (For example: 0.25). When uploading or downloading, the maximum allowed block size is 0.75 * AZCOPY_BUFFER_GB. To learn more, see [Optimize memory use](storage-use-azcopy-optimize.md#optimize-memory-use).
 
 `--check-md5`    (string)    Specifies how strictly MD5 hashes should be validated when downloading. This option is only available when downloading. Available values include: NoCheck, LogOnly, FailIfDifferent, FailIfDifferentOrMissing. (default 'FailIfDifferent'). (default "FailIfDifferent")