Clustered Data ONTAP Concepts

Cluster-Mode Concepts as Physical or Logical:

Physical:

Node, Disk, Network Port, FC Port

Logical:

Aggregate, Vserver, Cluster, Volume, Snapshot Copy, Mirror, LIF

The Scope of Cluster-Mode Concepts:

Node Vserver :

Disk, Network Port, Aggregate, HBA

Cluster (Data) Vserver:

Namespace, Mirror, Data LIF, Volume, Snapshot Copy, LUN

Kernel and User-Space Processes:

The path of a NAS write request:

1 – NFS or CIFS client

2 – Data network port

3 – N-blade

4 – Cluster session manager (CSM)

5 – D-blade

6 – NVRAM

User-Space Processes:

- The management gateway daemon (mgwd)

- The volume location database (vldb)

- The vif manager (vifmgr)

- The block data access configuration (bcomd)

- The clustershell (ngsh)

- The NDMP daemon (ndmpd)

- NFS and CIFS authentication (secd)

- The service process manager daemon (spmd)

RDB and Quorum Concepts:

 The four RDB (replicated database) units:

Management, VifMgr, VLDB, BCOM

The Management RDB unit: keeps track of the data that is used to operate the clustershell.

The VLDB RDB unit: keeps track of the volumes and aggregates and which volumes are on which aggregates.

To maintain quorum in a cluster either requires either (N/2) +1 healthy nodes or N/2 with one of them being the Epsilon node.

The update to the VLDB is made to the copy of the VLDB database that lives on the VLDB master. That master then syncs to the other (secondary) VLDB databases with itself. That entire sequence is considered to be an atomic transaction (non-divisible / all-or-nothing).

An n-node cluster contains n local VLDB databases.

An n-node cluster contains 4n local RDB databases.

VOL0 Volumes Uses and Limitations:

The minimum number of vol0 volumes in a 20-node cluster = 20

The maximum number of vol0 volumes in a 20-node cluster = 20

In the vol0 volume is stored:

log files, RDB databases

Characteristics of vol0 and vsroot:

vol0 and vsroot are flexible volumes.

Characteristics of vol0:

vol0 can be accessed by the local FreeBSD shell.

vol0 cannot be moved to another root aggregate.

Characteristics of vsroot:

vsroot can have snapshot copies.

vsroot can have mirrors.

vsroot can be accessed by NFS or CIFS clients.

vsroot can be backed up to tape.

vsroot can be copied.

vsroot can have junctions to other volumes.