AFF Systems And Cloud Volumes ONTAP: Better Together

One or multiple RAID groups form an "aggregate", and within aggregates ONTAP operating system sets up "flexible volumes" (FlexVol) to store data that users can access. Similar to RAID 0, each aggregate consolidates space from underlying protected RAID groups to provide one logical piece of storage for flexible volumes. Alongside aggregates of NetApp's disks and RAID groups aggregates could consist of LUNs already protected with third-party storage systems with FlexArray, ONTAP Select, or Cloud Volumes ONTAP. Each aggregate could consist of either LUNs or NetApp's RAID groups. An alternative is "traditional volumes" where one or more RAID groups form a single static volume. Flexible volumes offer the advantage that many of them can be created on a single aggregate and resized at any time. Smaller volumes can then share all of the spindles available to the underlying aggregate and with a combination of storage, QoS allows the performance of flexible volumes to be changed on the fly while traditional volumes do not. However, traditional volumes can (theoretically) handle slightly higher I/O throughput than flexible volumes (with the same number of spindles), as they do not have to go through an additional virtualization layer to talk to the underlying disk. Aggregates and traditional volumes can only be expanded, never contracted. The current maximum aggregate physical useful space size is 800 TiB for All-Flash FAS Systems.[citation needed]

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The uniqueness of NetApp's Clustered ONTAP is in the ability to add heterogeneous systems (where all systems in a single cluster do not have to be of the same model or generation) to a single cluster. This provides a single pane of glass for managing all the nodes in a cluster, and non-disruptive operations such as adding new models to a cluster, removing old nodes, online migration of volumes, and LUNs while data is contiguously available to its clients.[17] In version 9.0, NetApp renamed Data ONTAP to ONTAP.

FAS and AFF storage systems use enterprise level HDD and SSD drives that are housed within disk shelves that have two bus ports, with one port connected to each controller. All of ONTAP's disks have an ownership marker written to them to reflect which controller in the HA pair owns and serves each individual disk. An Aggregate can include only disks owned by a single node, therefore each aggregate owned by a node and any upper objects such as FlexVol volumes, LUNs, File Shares are served with a single controller. Each controller can have its own disks and aggregates and serve them, therefore such HA pair configurations are called Active/Active where both nodes are utilized simultaneously even though they are not serving the same data.

Is a feature of ONTAP Select software, similarly to MetroCluster on FAS/AFF systems MetroCluster SDS (MC SDS) allows to synchronously replicate data between two sites using SyncMirror and automatically switch to survived node transparently to its users and applications. MetroCluster SDS work as ordinary HA pare so data volumes, LUNs and LIFs could be moved online between aggregates and controllers on both sites, which is slightly different than traditional MetroCluster on FAS/AFF systems where data cloud be moved across storage cluster only within site where data originally located. In traditional MetroCluster the only way for applications to access data locally on remote site is to disable one entire site, this process called switchover where in MC SDS ordinary HA process occurs. MetroCluster SDS uses ONTAP Deploy as the mediator (in FAS and AFF world this functionality known as MetroCluster tiebreaker) which came with ONTAP Select as a bundle and generally used for deploying clusters, installing licenses and monitoring them.

ONTAP provide two techniques for Multi Tenancy functionality like Storage Virtual Machines and IP Spaces. On one hand SVMs are similar to Virtual Machines like KVM, they provide visualization abstraction from physical storage but on another hand quite different because unlike ordinary virtual machines SVMs does not allow to run third party binary code like in Pure storage systems; they just provide virtualized environment and storage resources instead. Also SVMs unlike ordinary virtual machines do not run on a single node but for the end user it looks like an SVM runs as a single entity on each node of the whole cluster. SVM divides storage system into slices, so a few divisions or even organizations can share a storage system without knowing and interfering with each other while utilizing same ports, data aggregates and nodes in the cluster and using separate FlexVol volumes and LUNs. Each SVM can run its own frontend data protocols, set of users, use its own network addresses and management IP. With use of IP Spaces users can have the same IP addresses and networks on the same storage system without interfering. Each ONTAP system must run at least one Data SVM in order to function but may run more. There are a few levels of ONTAP management and Cluster Admin level has all of the available privileges. Each Data SVM provides to its owner vsadmin which has nearly full functionality of Cluster Admin level but lacks physical level management capabilities like RAID group configuration, Aggregate configuration, physical network port configuration. However, vsadmin can manage logical objects inside an SVM like create, delete and configure LUNs, FlexVol volumes and network addresses, so two SVMs in a cluster can't interfere with each other. One SVM cannot create, delete, modify or even see objects of another SVM, so for SVM owners such an environment looks like they are the only users in the entire storage system cluster. Multi Tenancy is free functionality in ONTAP.

FlexGroup is a free feature introduced in version 9, which utilizes the clustered architecture of the ONTAP operating system. FlexGroup provides cluster-wide scalable NAS access with NFS and CIFS protocols.[19] A FlexGroup Volume is a collection of constituent FlexVol volumes distributed across nodes (up to 200 per FlexGroup) in the cluster called just "Constituents" or "member volumes", which are transparently aggregated in a single space. Therefore, FlexGroup Volume aggregates performance and capacity from all the Constituents and thus from all nodes of the cluster where they located, as well as parallelizing CPU cores per node for write metadata-heavy operations. For the end user, each FlexGroup Volume is represented by a single, ordinary NAS (SMB or NFS) file-share.[20] The full potential of FlexGroup will be revealed with technologies like pNFS (added in ONTAP 9.7), NFS Multipathing (session trunking, announced in ONTAP 9.12.1) SMB multichannel (added in ONTAP 9.4), SMB Continuous Availability (FlexGroup with SMB CA shares Supported with ONTAP 9.6), and VIP (BGP). The FlexGroup feature in ONTAP 9 allows to massively scale in a single namespace to over 20PB with over 400 billion files, while evenly spreading the performance across the cluster.[21] Starting with ONTAP 9.5 FabricPool (automatic cloud tiering for storage efficiency) support was added. ONTAP 9.5 also added support for SMB features for native file auditing, FPolicy, Storage Level Access Guard (SLA), copy offload (ODX) and inherited watches of changes notifications; Quotas and Qtree. SMB Contiguous Availability (CA) supported on FlexGroup allows running MS SQL & Hyper-V on FlexGroup, and FlexGroup supported on MetroCluster. For more information about FlexGroup volumes and supported features, see TR-4571: NetApp ONTAP FlexGroup Volumes Best Practice and Implementation Guide.

SnapMirror Sync (SM-S) for short is zero RPO data replication technology previously available in 7-mode systems and was not available in (clustered) ONTAP until version 9.5. SnapMirror Sync replicates data on Volume level and has requirements for RTT less than 10ms which gives distance approximately of 150 km. SnapMirror Sync can work in two modes: Full Synchronous mode (set by default) which guarantees zero application data loss between two sites by disallowing writes if the SnapMirror Sync replication fails for any reason. Relaxed Synchronous mode allows an application to write to continue on primary site if the SnapMirror Sync fails and once the relationship resumed, automatic re-sync will occur. SM-S supports FC, iSCSI, NFSv3, NFSv4, SMB v2 & SMB v3 protocols and have the limit of 100 volumes for AFF, 40 volumes for FAS, 20 for ONTAP Select and work on any controllers which have 16GB memory or more. SM-S is useful for replicating transactional logs from: Oracle DB, MS SQL, MS Exchange etc. Source and destination FlexVolumes can be in a FabricPool aggregate but must use backup policy, FlexGroup volumes and quotas are not currently supported with SM-S. SM-S is not free feature, the license is included in the premium bundle. Unlike SyncMirror, SM-S not uses RAID & Plex technologies, therefore, can be configured between two different NetApp ONTAP storage systems with different disk type & media.

FlexCache technology previously available in 7-mode systems and was not available in (clustered) ONTAP until version 9.5. FlexCache allows serving NAS data across multiple global sites with file locking mechanisms. FlexCache volumes can cache reads, writes, and metadata. Writes on the edge generating push operation of the modified data to all the edge ONTAP systems requested data from the origin, while in 7-mode all the writes go to the origin and it was an edge ONTAP system's job to check the file haven't been updated. Also in FlexCache volumes can be less size that original volume, which is also an improvement compare to 7-mode. Initially, only NFS v3 supported with ONTAP 9.5. FlexCache volumes are sparsely-populated within an ONTAP cluster (intracluster) or across multiple ONTAP clusters (inter-cluster). FlexCache communicates over Intercluster Interface LIFs with other nodes. Licenses for FlexCache based on total cluster cache capacity and not included in the premium bundle. FAS, AFF & ONTAP Select can be combined to use FlexCache technology. Allowed to create 10 FlexCache volumes per origin FlexVol volume, and up to 10 FlexCache volumes per ONTAP node. The original volume must be stored in a FlexVol while all the FlexCache Volumes will have FlexGroup volume format.

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