NetApp Terminology

Now that we know how a NetApp is configured from a hardware point of view, we now need to know how to present the storage to the outside world, first some NetApp terminologies explained

Aggregate:

A collection of disks that can have either of the below RAID levels, the aggregate can contain up to 1176 disks, you can have many aggregates with the below different RAID levels. An aggregate can contain many volumes (see volumes below).

• RAID-4
• RAID-DP (RAID-6) better fault tolerance

One point to remember is that a aggregate can grow but cannot shrink, the disadvantage with RAID 4 is that a bottleneck can happen on the dedicated parity disk, which is normally the first disk to fail due to it being used the most, however the NVRAM helps out by only writing to disks every 10 seconds or when the NVRAM is 50% full.

Raid Group (Pool)
Normally there are three pools 0, 1 and spare

• 0 = normal pool
• 1 = mirror pool (if syncMirror is enabled)

spare = spares disks that be used for growth and replacement of failed disks

Plex

When a aggregate is mirrored it will have two plexes, when thinking of plexes think of mirroring. A mirrored aggregated can be split into two plexes.

Volume (Flexible)

This is more or like a traditional volume in other LVM's, it is a logical space within an aggregate that will contain the actual data, it can be grown or shrunk as needed

WAFL

Write anywhere filesystem layout is the filesystem used, it uses inodes just like Unix. Disks are not formatted they are zeroed.

By default WAFL reserves 10% of a disk space (unreclaimable)

LUN

The Logical Unit Number is what is present to the host to allow access to the volume.

SNAPSHOT

A frozen read-only image of a volume or aggregate that reflects the state of the new file system at the time the snapshot was created, snapshot features are

• Up to 255 snapshots per volume
• can be scheduled
• Maximum space occupied can be specified (default 20%)

File permissions are handled