NetApp Basics

Root Volume:

·         Root volume hold all the ONTAP files. It always preferred to separate the root volume from Data volumes. Better options to restrict the root volume to just 2 disk. This enables faster reconstruction times in case of a disk failure on the root volume.

Volume Snapshot Reserve:

·         Default volume snapshot space reserve is 20% of the volume size.  As snapshot copies need a space, they consume space in the snap reserve area. The snapshot copies will start consume the volume space if it is get filled up, Better options to enable the autodelete snapshot options to avoid volume filed up and write error issue.

Aggregate Reserve:

·         Default Aggregates are created by default with 5% of reserve space.

The aggregate space is calculated as below:

Aggregate usable size = disk capacity X number of disks X 0.90 X 0.95

ð  Thumb rule of 2 disk hot spares is applied for every 30 disks

ð  Snapshot reserve default 5% for aggregate and 20% for flexvolume

ð  Snapshot for LUNS are subject to space reservation. It might be null or fractional

WAFL (Write anywhere file layout) overhead:

·         WAFL reserves approximately 10% of space for performance reason and meta data.

Spare Disks allocation:

·         It depends upon your space and data protection calculation.

As per NetApp suggestion:

On NetApp storage, disk failures automatically trigger parity reconstructions of affected data onto a hot standby (spare) disk, assuming that a spare disk is available. If no spare disks are available, self-healing operations are not possible. The system will run in degraded mode (requests for data on the failed disk are satisfied by reconstructing the data using parity information) until a spare is provided or the failed disk is replaced. During this time, your data is at greater risk should an additional failure occur. (With NetApp RAID-DP™, a RAID group operating in degraded mode can undergo one additional disk failure without suffering data loss.)
The number of spares you need varies based on the number of disk drives attached to your storage system. For a lower-end FAS200 or FAS2000 with a single shelf, one spare disk may suffice (configure two if you want to use Maintenance Center). On the FAS6080, with a maximum spindle count of 1,176 disks, more spare disks are needed to ensure maximum storage resiliency, especially with larger SATA disks that have longer reconstruction times.
NetApp recommends using two spares per disk type for up to 100 disk drives, where disk type is determined by a unique interface type (FC, SATA, or SAS), capacity, and rotational speed. For instance, if you have a system with 28 300GB 15K FC disks and 28 144GB 15K FC disks, you should provide four spares: two of the 300GB capacity and two of the 144GB capacity.

Calculate the disk size:

·         Storage hard disk is using the base system and software is using the base 2 system.

Hard disk manufacturers assume Base 10 System Killo = 10 the power of 3

File system assumes Killo = 2th power of 10 = 2X2X2X2X2X2X2X2X2X2=1024

1TB hard disk is actual size :

1000,000,000 bytes/ 1,073,741,824  = .9313 x 1000 = 931.3 GB