NetApp storage efficiency

1. How NetApp MyAutosupport Dashboard Storage Efficiency calculations are done?

2. My Autosupport Dashboard reports following Storage Efficiency chart
Reported savings in ‘% percentile’ is usually shown when you click ‘see more details’ under storage
efficiency tab.
Question is: How these 4 values are derived?
Obviously, these numbers are result of some formula used for the calculations, so let’s see what
these formulas are:

3. Formula for Storage Utilization Calculations:
Storage Utilization = Used Capacity / Usable Capacity
RAW storage Utilization = Used Capacity / RAW capacity
Formula for Storage Efficiency Calculations:
Storage Efficiency = Effective Used Capacity / Usable capacity
RAW storage Efficiency = Effective Used Capacity / RAW capacity
Next, we must know the definition of these parameters used in the calculations. This is how NetApp
has defined them.
 Used Capacity = Usable Capacity - Free Capacity - Space (Unused) Reserve
 Raw Capacity = Disk Drives x Labelled Disk Drives Capacity
 Usable Capacity = Raw Capacity - System Reserve Capacity
 Effective Used Capacity = Used Capacity + Efficiency Returns
For information on what Efficiency Returns, Free Capacity, Space Reserve, Labelled Disk Drives
Capacity and System Reserve Capacity means, please refer to the TR from NetApp:
www.netapppartneruk.com/downloads/tr-3827.pdf
Now, that we know the formula, let’s see how these number are derived.

4. Let’s take another look at the Storage Efficiency chart and pin-point where these numbers come
from:
If you are wondering, how values mentioned above is actually derived, just refer to definitions of
each parameter on page 2.
Now, put them into equation and substitute the values:
Used Capacity = Usable Capacity - Free Capacity - Space (Unused) Reserve
= 13.09 - 2.82 - 1.10
= 9.17 TB
Usable Capacity = Raw Capacity - System Reserve Capacity
= 19.4 – (4.85 + 1.46)
= 19.4 – 6.31
= 13.09 TB
Effective Used Capacity is little tricky hence it is explained later.

5. Finally, let’s put these values into the Storage Efficiency formula one by one.
# 1 – Starting with RAW storage Efficiency:
As per the NetApp report we expect to see 70 % Raw Storage Efficiency.
RAW storage Efficiency = Effective Used Capacity / RAW capacity
= 13.61 / 19.4 * 100
= 0.70 * 100
= 70 %
# 2 – Next, RAW storage Utilization :
RAW storage Utilization = Used Capacity / RAW capacity
= 9.17 / 19.4 * 100
= 0.47 * 100
= 47 %
# 3 – Next, Storage Efficiency :
Storage Efficiency = Effective Used Capacity / Usable capacity
= 13.61 / 13.09 * 100
= 1.039 * 100
= 104 %
# 4 – Finally, Storage Utilization :
Storage Utilization = Used Capacity / Usable Capacity
= 9.17 / 13.09 * 100
= 0.70 * 100
= 70 %

6. Among all the parameters mentioned, the trickiest part is Effective Used Capacity, so how this value
is generated?
As per the NetApp document, Effective Used Capacity = Used Capacity + Efficiency Returns
We know the first two values very clear:
 Effective Used Capacity = 13. 61 TB
 Used Capacity = 9.17 TB
 Efficiency Returns = what does this constitutes?
As per NetApp TR-3827, it covers various saving parameters such as:
Capacity saved by: Cloning + Deduplication + Snapshot + RAID-DP + Thin Provisioning.
That means, if we want to find out Effective Used Capacity, we simply add Used Capacity + Efficiency
Returns?
Let’s see if this works:
Effective Used Capacity = Used Capacity + Efficiency Returns
= 9.17 + 2.94 (Snapshot copies) + 1.5 (Dedupe)
= 13.61 TB
Note: Even though there are 6 saving parameters in the chart; RAID-DP, Thin Provisioning &
SnapVault Secondary figures are not taken into consideration for ‘Effective Used Capacity’
calculation.
-Prepared by
ashwinwriter@gmail.com