ViPR 2.1 - EMC ViPR Support For Meta Volumes on VMAX and VNX Arrays

EMC ViPR support for meta volumes on VMAX and VNX arrays

EMC ViPR manages, creates, and modifies VMAX and VNX meta volumes when it creates and expands volumes on an EMC VMAX or EMC VNX array.

ViPR provides a number of services that create volumes on block storage:

Block Storage Services > Create Block Volume
Block Storage Services > Create Block Volume for a Host
Block Services for Windows > Create and Mount Volume
Block Services for Linux > Create and Mount Volume

ViPR also provides services that expand block storage volumes.

Block Storage Services > Expand Block Volume
Block Services for Windows > Expand Volume on Windows
Block Services for Linux > Expand Linux Mount

This article applies to ViPR 2.0 and ViPR 2.1.

Concatenated vs. striped meta volumes on VMAX arrays

VMAX supports both striped and concatenated meta volumes. ViPR enables you to control the type of meta volume it creates.

By default, ViPR creates striped meta volumes. However, you control the type of meta volume that ViPR creates.

VMAX supports both striped and concatenated meta volumes.

If you enable Fast Expansion,ViPR creates concatenated meta volumes in this virtual pool. If Fast Expansion is disabled, ViPR creates striped meta volumes.

The Fast Expansion option is available in the virtual pool configuration screens only if you select a system type of EMC VMAX or EMC VNX Block.

ViPR striped volume creation in a VMAX thin pool

When a ViPR user submits a request to create a striped volume in a thin storage pool, ViPR determines whether to create a regular volume or a meta volume.

The following list describes the process and policies that ViPR uses to determine when and how to build striped volumes in a thin pool.

During VMAX array discovery, ViPR adds physical storage pools.
Each storage pool has an associated maximum volume size.
You can retrieve the maximum volume size for a storage pool by performing a GET against that storage pool using the ViPR REST API.
The default maximum volume size of a storage pool on a VMAX is 240 GB. You can explicitly set the maximum volume size for a VMAX storage pool through the auto meta feature.
If the VMAX auto meta feature is enabled, the maximum volume size is the min_auto_meta_size setting of the array.
If you modify the min_auto_meta_size setting of any array under ViPR management from Unisphere, the best practice is to immediately rediscover the array in order to synchronize the array settings with ViPR. If you do not rediscover the array, any volume creation or expansion could yield unpredictable results.
ViPR chooses one physical storage pool where it will create the volume. (ViPR volumes do not span across physical storage pools.)
ViPR checks the maximum volume size of the storage pool and compares it to the size of the request that the user submitted through the service dialog box.
If the requested volume size exceeds the maximum volume size of the storage pool, ViPR creates a meta volume. If the requested volume size is smaller than the maximum volume size of the storage pool, ViPR creates a standard volume.

Striped thin pool provisioning: Determine the number of meta members in a meta volume

When ViPR creates a striped meta volume in a virtual pool that has thin provisioning, it calculates how many meta members to build according to the following rules:

ViPR retrieves the maximum meta member size from the storage pool object that ViPR returned from an array discovery. (The default is 240GB.)
If the requested volume size exceeds the maximum thin volume meta member size limit, build a meta volume. For requests smaller than the maximum thin volume meta member size limit, create a regular volume.
Use 8 members total (including the head) until you reach the maximum capacity possible of 8 members. An eight member meta volume includes a meta head and seven meta members.
If an 8 member meta volume is too small to fulfill the request, use a 16-member meta volume. If the 16-member meta volume is too small, use a 32-member meta volume.
When requested capacity exceeds 32 meta members, add more members individually, for example, 33, 34, 35, until you achieve sufficient capacity.

ViPR concatenated volume creation on VMAX

When a ViPR user submits a request to create a concatenated volume, ViPR determines whether to create a regular volume or a meta volume.

Concatenated vs striped meta volumes describes the virtual pool settings you must set to force ViPR to create a concatenated meta volume.

The following list describes the process and policies that ViPR uses to determine when and how to build concatenated meta volumes.

During VMAX array discovery, ViPR adds physical storage pools.
Each storage pool has an associated maximum volume size.
You can retrieve the maximum volume size for a storage pool by performing a GET against that storage pool using the ViPR REST API.
The default maximum volume size of a storage pool on a VMAX is 240 GB. You can explicitly set the maximum volume size for a VMAX storage pool through the auto meta feature.
If the VMAX auto meta feature is enabled, the maximum volume size is the min_auto_meta_size setting of the array.
If you modify the min_auto_meta_size setting of any array under ViPR management from Unisphere, the best practice is to immediately rediscover the array in order to synchronize the array settings with ViPR. If you do not rediscover the array, any volume creation or expansion could yield unpredictable results.
ViPR chooses one physical storage pool where it will create the volume. (ViPR volumes do not span across physical storage pools.)
ViPR checks the maximum volume size of the storage pool and compares it to the size of the request that the user submitted through the service dialog box.
If the requested volume size exceeds the maximum volume size of the storage pool, ViPR creates a meta volume. If the requested volume size is smaller than the maximum volume size of the storage pool, ViPR creates a standard volume.

After ViPR chooses a storage pool, it creates the volume.

Concatenated meta volume: Determine the number of meta members in a meta volume

When ViPR creates a concatenated meta volume, it sets the number of meta members according to the following process:

Determine the maximum volume size. The ViPR API GET on the storage pool returns this information.
Create the number of meta members that ViPR needs to fulfill the request.
Ensure that all created meta members are the same size.

Example 1

Suppose the VMAX returns a maximum volume size of 240 GB.

The user asks ViPR to create a 400 GB volume.

ViPR creates 2 meta members of 200 GB apiece.

Example 2

Suppose the VMAX a maximum volume size returned of 240 GB.

The user asks ViPR to create a 900 GB volume.

ViPR creates 4 meta members of 225 GB apiece.

ViPR striped volume creation in a VMAX thick pool

When a ViPR user submits a request to create a striped volume in a thick storage pool, ViPR determines whether to create a regular volume or a meta volume.

ViPR uses the following process and policies to determine when and how to build striped volumes in a thick pool.

During VMAX array discovery, ViPR adds physical storage pools.
Each storage pool has an associated maximum volume size.
You can retrieve the maximum volume size for a storage pool by performing a GET against that storage pool using the ViPR REST API.
The default maximum volume size of a storage pool on a VMAX is 240 GB. You can explicitly set the maximum volume size for a VMAX storage pool through the auto meta feature.
If the VMAX auto meta feature is enabled, the maximum volume size is the min_auto_meta_size setting of the array.
If you modify the min_auto_meta_size setting of any array under ViPR management from Unisphere, the best practice is to immediately rediscover the array in order to synchronize the array settings with ViPR. If you do not rediscover the array, any volume creation or expansion could yield unpredictable results.
ViPR chooses one physical storage pool where it will create the volume. (ViPR volumes do not span across physical storage pools.)

Striped thick pool provisioning: Determine the number of meta members in a meta volume

When ViPR creates a striped meta volume in a storage pool that has thick provisioning, it calculates how many meta members to build according to the following rules:

If the request is between 32GB and 500GB, use a 4-member meta volume.
If the request is between 500GB to 1024GB, use an 8-member meta volume.
More than 1024GB, use a 16-member meta volume or a 32-member meta volume, according to requested capacity.
When requested capacity is larger than 32 meta members, add more members individually. For example, add a 33rd meta member, then a 34th, until you reach sufficient capacity.

ViPR volume expansion on VMAX

You can expand a volume on a VMAX if the volume was created in a virtual pool that has the Expandable option enabled. When a ViPR user submits a request to expand a VMAX volume, ViPR applies the following rules:

Any volume expansion on VMAX results in a meta volume. This is a VMAX feature. Therefore, if you expand a volume that resides on a VMAX with ViPR, the resulting volume will be a meta volume, even if the original volume was a regular volume and the expansion was small.
If you expand a meta volume with a ViPR service, ViPR adds meta members until the total size of the volume meets or exceeds the size that the user specified in the service request.
If the meta volume is a striped meta, striped data is redistributed to use new member volumes. This process can take some time. VMAX backs up the volume data to a BCV (Business Continuity Volume). Then it creates a striped meta volume of the requested size and copies the data to it.
All meta members in a meta volume have the same size. For example:
- When ViPR expands a 256GB meta volume with 8 members to 320GB, it adds two new members, each of 32GB.
- When ViPR expands a 16GB regular volume to 256GB, ViPR adds 15 new members, each of 16GB.
When ViPR expands a regular VMAX volume into a meta volume, the result is a concatenated meta volume of the requested size.
Expect some delays in accessing the data while expansion service processing is under way.

ViPR meta volume creation on VNX: notes and guidelines

When ViPR creates volumes in a VNX storage pool, it applies the following guidelines:

During VNX array discovery, ViPR adds physical storage pools.
Each storage pool has an associated maximum volume size.
You can retrieve the maximum volume size for a storage pool by performing a GET against that storage pool using the ViPR REST API.
VNX supports meta volumes only for RAID groups (volumes created in concrete pools). They are always thick volumes.
ViPR creates meta volumes for all VNX volumes larger than the maximum meta member size that the VNX array returns. The default volume size limit for a thick volume in a concrete storage pool on a VNX is 1.7TB.
On a VNX, unified storage pools support only regular volumes.
When ViPR creates meta members in meta volumes, those meta members are the same size.
ViPR creates striped meta volumes on VNX. ViPR does not create concatenated meta volumes on a VNX array.
If a concatenated meta volume resides on the VNX outside of ViPR, ViPR can ingest it. Subsequently, ViPR can expand that concatenated meta volume.

ViPR provisioning on VNX: regular vs. meta volumes

When ViPR receives a request to create a volume on a VNX array, it uses the certain criteria to determine the type of volume to create.

To determine the type of volume to create on the VNX, ViPR completes the following processes:

ViPR chooses one physical storage pool where it will create the volume. ViPR volumes do not span across physical storage pools.
If you specify a thin virtual storage pool in the service dialog box, ViPR provisions a regular volume up to the maximum volume size for the physical storage pool.
If you specify a thick virtual storage pool in the service dialog, ViPR checks the maximum volume size of the storage pool and compares it to the size of the request that the user requested through the service dialog box.
If the requested volume size exceeds the maximum volume size of the storage pool, ViPR creates a meta volume. If the requested volume size is less than the maximum volume size of the storage pool, ViPR creates a standard volume.

ViPR provisioning on VNX: Determine the number of meta members in a volume

During storage provisioning, ViPR uses the following processes to determine the number of members to create in the meta volume:

ViPR builds the minimum number of meta members to fulfill the request.
ViPR creates meta members that are all the same size.
No meta member exceeds the maximum meta member size. The value of the maximum meta member size resides in the storage pool object that ViPR returns from a VNX array discovery.

ViPR meta volume creation on VNX: examples

The following examples assume that the maximum volume size in the concrete storage pools is 1.7TB.

The user requests a volume of 6 TB. ViPR creates a meta volume that has 4 meta members of 1.5 TB.

The user requests a volume of 10 TB. ViPR creates a meta volume that has 6 1.7 TB meta members.

Expand a volume on a VNX array

You can expand a volume on a VNX if the volume was created in a virtual pool that has the Expandable option enabled. When you expand a VNX volume, ViPR applies these policies:

Thin Pool Volumes. Either thick or thin LUNs created in VNX Unified pools. ViPR expands these volumes as regular volumes up to the regular volume size limit in the storage pool. ViPR does not support meta volume expansion of these volumes. The volume size limit for thick volumes in a Unified CLARiiON storage pool is 11TB. The size limit for thin volumes is 17TB.
Thick pool volumes. RAID group volumes that are thick LUNs provisioned from VNX concrete pools. ViPR expands them as meta volumes.