Calculating Physical Disk Space for Licensed NetVault: SmartDisk Capacity
Posted by Dawn renee Campbell on March 8, 2010
Dawn renee Campbell, Senior Product Manager for NetVault: SmartDisk & NetVault: Backup
After you have determined how much NetVault: SmartDisk (NVSD) capacity you need to license, the next step is calculating how much physical disk space you will need.
As we discovered in my Calculating NetVault: SmartDisk License Capacity blog, NVSD is licensed based on the Logical Capacity of the data that it can store. However, in Deduplicated NVSD Instances, Logical Capacity does not match Physical Capacity or physical disk space. This is because NVSD Deduplication Option packs up to 12 times more protected data into the same storage area for a 92% reduction in storage footprint.
Deduplicated NVSD Instances
A Deduplicated NVSD Instance can have a combination of both Deduplicated and Non-Deduplicated data. In this configuration, calculating the total Physical Capacity or physical disk space is comprised by calculating the Physical Capacity for the Deduplicated Backups followed by calculating the Physical Capacity for the Non-Deduplicated Backups and totaling the sums.
Deduplicated Backups
The Physical Capacity or physical disk space required for Deduplicated Backups in Deduplicated NVSD Instances is equal to the Size of Weekly Full Backups + Unique Data Size and is calculated using the following formula:
(Size of Weekly Full Backups) +
Size of Weekly Full Backups + ((Size of Weekly Full Backups * Weekly Change Rate)
* Weekly Full Backup Retention Period)
+ (Size of Daily Backups * (Number of Daily Backups between Weekly Full Backups
* Daily Backup Retention Period))
Non-Deduplicated Backups
The Physical Capacity or physical disk space required for Non-Deduplicated Backups in a Deduplicated NVSD Instance is calculated using the following formula:
(Size of Non-Deduplicated Weekly Full Backups * Weekly Full Backup Retention Rate)
+ (Size of Non-Deduplicated Daily Backups * (Number of Daily Backups between Full Backups * Daily Backup Retention Period in Weeks))
Total Required Disk Space = Deduplicated Backup Disk Space + Non-Deduplicated Backup Disk Space
The Total Required Disk Space is divided into the Staging Store and the Chunk Store. If different file systems or disk spindles are going to be utilized for the Staging Store and the Chunk Store, it is important to know how much of the Total Required Disk Space will be allocated to the Staging Store versus the Chunk Store. The calculations below can be used to make this determination.
Calculating Staging Store Size
The amount of time a Deduplicated Backup remains in the Staging Store is different than the amount of time a Non-Deduplicated Backup will remain in the Staging Store. Therefore, to determine the total disk space required for the Staging Store, the size required for both Deduplicated Backups and Non-Deduplicated Backups must be calculated and totaled.
Total Staging Store Disk Space = Deduplicated Backup Disk Space + Non-Deduplicated Backup Disk Space
Deduplicated Backups
During the NVSD Deduplicated Backup process, backups are initially streamed to the Staging Store where they remain until the deduplication process is completed. The Staging Store must be big enough to hold all the Deduplicated Backups while they are awaiting deduplication.
If the deduplication window overlaps the backup window, deduplication and backups will occur at the same time. Each backup will start deduplicating once the backup job is completed. Additionally, large backups will be broken into 400GB segments. Each segment will start to deduplicate once it is received even if the backup stream is still being streamed to the Staging Store. Therefore, the Staging Store only requires space to hold some portion of the total backup size. If the Staging Store runs out of space, backups will pause until space becomes available such as when a deduplication operation completes.
The maximum disk space required for the Staging Store is equal to the Size of the Weekly Full Backups.
Non-Deduplicated Backups
Backups that are not deduplicated are streamed into the Staging Store where they will remain until they are retired. Therefore, calculating the size of Staging Store for Non-Deduplicated Backups is identical to calculating the required physical disk space required for Non-Deduplicated Backups in a Deduplicated NVSD Instance.
(Size of Non-Deduplicated Weekly Full Backups * Weekly Full Backup Retention Rate)
+ (Size of Non-Deduplicated Daily Backups * (Number of Daily Backups between Full Backups * Daily Backup Retention Period in Weeks))
Calculating Chunk Store Size
The amount of physical disk space required for the Chunk Store is equal to the Unique Data Size. To calculate the Unique Data Size or the size of the Chunk Store, use the following formula:
Size of Weekly Full Backups + ((Size of Weekly Full Backups * Weekly Change Rate)
* Weekly Full Backup Retention Period)
+ (Size of Daily Backups * (Number of Daily Backups between Weekly Full Backups
* Daily Backup Retention Period))
Non-Deduplicated NVSD Instances
The Physical Capacity or physical disk space required for Non-Deduplicated NVSD Instances is equal to the Logical Capacity because deduplication has been disabled. The Non-Deduplicated NVSD Instance will consume the same amount of disk space for the Staging Store as Logical Capacity that is being licensed.
NVSD Sizing Calculator
Not only does the NetVault: SmartDisk Sizing Calculator let you simply calculate the NVSD Capacity you need to license, it will also tell you the estimated physical capacity. If you haven’t already obtained it, you can ask your BakBone Representative for the NVSD Sizing Calculator.
In my next NVSD blog, we will explore where to deploy your NVSD Instances.
