How NetApp MyAutosupport Dashboard Storage Efficiency calculations are done?
My Autosupport Dashboard reports following Storage Efficiency chartReported savings in ‘% percentile’ is usually shown when you click ‘see more details’ under storageefficiency 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 whatthese formulas are:
Formula for Storage Utilization Calculations:Storage Utilization = Used Capacity / Usable CapacityRAW storage Utilization = Used Capacity / RAW capacityFormula for Storage Efficiency Calculations:Storage Efficiency = Effective Used Capacity / Usable capacityRAW storage Efficiency = Effective Used Capacity / RAW capacityNext, we must know the definition of these parameters used in the calculations. This is how NetApphas 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 ReturnsFor information on what Efficiency Returns, Free Capacity, Space Reserve, Labelled Disk DrivesCapacity and System Reserve Capacity means, please refer to the TR from NetApp:www.netapppartneruk.com/downloads/tr-3827.pdfNow, that we know the formula, let’s see how these number are derived.
Let’s take another look at the Storage Efficiency chart and pin-point where these numbers comefrom:If you are wondering, how values mentioned above is actually derived, just refer to definitions ofeach 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 TBUsable Capacity = Raw Capacity - System Reserve Capacity= 19.4 – (4.85 + 1.46)= 19.4 – 6.31= 13.09 TBEffective Used Capacity is little tricky hence it is explained later.
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 %
Among all the parameters mentioned, the trickiest part is Effective Used Capacity, so how this valueis generated?As per the NetApp document, Effective Used Capacity = Used Capacity + Efficiency ReturnsWe 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 + EfficiencyReturns?Let’s see if this works:Effective Used Capacity = Used Capacity + Efficiency Returns= 9.17 + 2.94 (Snapshot copies) + 1.5 (Dedupe)= 13.61 TBNote: 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 firstname.lastname@example.org