HP D2D Manual page 20

Device Streams: Device streams must be spread across the number of storage policies that could
run simultaneously to CommVaultShare1. In this case we plan to have only one storage policy to
CommVaultShare1, so we can allocate 12 streams. What this means is that we could back up 12
hosts simultaneously to CommVaultShare 1 by setting Device Streams (General tab) and Allocate
number of writers (Mount Paths tab) to 12.
Do not check Enable Stream Randomization because this will disrupt the deduplication efficiency
of the HP D2D NAS share.
NOTE: If you are backing up multiple hosts, you may like to create separate folders for each
host within the CommVaultShare1 library. Use Windows Explorer to do this.
Setting the Container/Chunk size
When using D2D NAS the CommVault backup software allocates a size to the containers (Chunks
in CommVault terminology) where the user data files will be stored on the Disk Library. The size
of these containers can be changed. D2D NAS has a fixed limit of 25000 files, so the larger we
make the containers the more data we can hold on the D2D NAS share. Ideally, the bigger the
containers the better as it stops us hitting the 25000 file limit and reduces fragmentation in the
backup. Set the container (chunk) size as follows:
1. Select the Storage Policy that we have just created and double click the storage policy in the
right—hand navigation window to get the Copy Properties window.
2. Click on the Data Paths tab in the Copy Properties window AND select the path.
3. Now click the Properties button at the bottom of the data paths page as shown below
Edit the Chunk size (MB) section to use a specific value and click OK. In this case we will
change the chunk size from 2048 (default) to 4096. The maximum chunk size is 32 GB, but
this can lead to some performance impact so typically a choice of 16 GB chunk size is a good
compromise.
20 Discover the NAS CIFS share in CommVault