About Network Managed Volume (NMV) Pools
The Network Managed Volumes (NMVs) option, a licensed product option, allows you to allocate and account for storage more efficiently. The NMV option allows you to create managed pools of storage from raw, unpartitioned, basic disks. NMVs are created from the NMV pools and ultimately mapped as virtual volumes to application servers as storage resources. NMVs are extended virtual devices in which the capacity presented to application servers may exceed the physical resources in the NMV pool. Additional physical space may be added to the pool non-disruptively as resources get low; capacity growth occurs transparently to the application server user. SANsymphony software can automatically allocate capacity via dynamic NMVs to provide just enough storage, just-in-time to application servers. NMVs eliminate the need for administrators to monitor usage on each application server to determine when they are likely to run out of disk space, while avoiding conventional disk resizing outages. When a virtual volume is mapped to an application server, the application server will be presented a volume whose size can be logical and determined by the operating system limitation only.
To add this feature to your license, contact your DataCore Sales Representative.
NMV pools
NMV pools are comprised of a collection of disks— even of different kinds— from JBOD (just a bunch of disks) enclosures to intelligent storage arrays. SANsymphony software enables users to centrally manage pooled storage resources. Refer to About Storage Devices for basics.
There are three types of pools: dynamic, static striped, and static spanned. These pool types and the virtual volumes created from them have distinct advantages and it is important to know the differences before creating pools. Refer to Pool Types for details.
Pools can eliminate the need for administrators to monitor usage on each application server to determine when they are likely to run out of disk space and avoid conventional disk resizing outages. Alerts can be set for dynamic pools. When a dynamic pool nears the alert threshold, notification is sent via alarms and event log messages of the pending need for more storage resources. Additional raw disks may be added to the pool non-disruptively as resources get low. When more physical storage is added to the pool, capacity growth occurs transparently to the application server user. Refer to Setting Alert Threshold.
Storage Allocation Units (SAUs)
When disks are added to pools, SANsymphony software carves units of available storage out of the resources. These units of storage, called storage allocation units (SAUs), have a size that is determined by the user when a pool is created and cannot be changed. SAUs can range in size from 1 MB to 2048 MB and must be a power of 2. The default size is 128 MB. A 128 MB SAU size can safely handle pools containing up to 1000 TB of storage resources. If you intend on adding more than 1000 TB of storage to the pool, you should increase the SAU size accordingly.
When NMVs (comprised of SAUs) are created from the pools, those SAUs are allocated. These SAUs are allocated either dynamically or statically as a function of how the NMV pool type is configured.
Ultimately, when a virtual volume is created from an NMV, the size of the virtual volume must be a multiple of the SAU size. Creating mirrored virtual volumes from pools of the same size SAUs allows for greater optimization.
NMVs
NMVs are used to create virtual volumes which are ultimately mapped to application servers as volumes for use.
NMVs from dynamic pool types are created, the default logical size is 2 terabyles (TB), although the physical size is the size of the SAU. Virtual volumes created from dynamic NMVs can be resized up to a maximum size of 1 petabyte (PB).) After the virtual volume is mapped, the application server will discover a volume whose size is determined by the logical size. When applications servers near full capacity for the volume they are using, SANsymphony software will automatically and seamlessly allocate another SAU to the volume, thereby giving the application server additional storage resources.
NMVs created from static pool types are not created with a default size. The size is fixed and allocated upon creation. When application servers reach full capacity on volumes created by static pools, users must map another virtual volume for additional storage resources.
Using Network Managed Volumes
Refer to the topics in the TOC under Configuration & Control/SANmanager>Pools and NMVs for all topics. Some include: