V8.4.1.x Configuration Limits and Restrictions for IBM Storwize V7000

1. VMware vSphere Virtual Volumes (vVols) are not supported in a DRP;
2. A volume in a DRP cannot be shrunk;
3. No volume move between I/O groups if volume in a DRP (use FlashCopy or Metro Mirror/Global Mirror instead);
4. No split of a volume mirror to copy in a different I/O group;
5. Real/used/free/free/tier capacity are not reported per volume - only per pool.

RAID and Distributed RAID
Storwize V7000 Generation 3 systems support DRAID5, DRAID6, TRAID0, TRAID1 and TRAID10. For compressed drives only DRAID5 and DRAID6 are supported.

DRAID Strip Size
For candidate drives, with a capacity greater than 4TB, a strip size of 128 cannot be specified for either RAID-5 or RAID-6 DRAID arrays. For these drives a strip size of 256 should be used.

Non-Disruptive Volume Move (NDVM)
The following Fibre Channel attached host types are supported for non-disruptively moving a volume between I/O groups (control enclosures):

Note: For all other host types, I/O should be quiesced when moving a volume.

When moving a volume that is mapped to a host cluster then you must rescan disk paths on all host cluster nodes to ensure the new paths have been detected before removing access from the original I/O group.

Clustered Systems
A system requires native Fibre Channel SAN or alternatively 8Gbps/16Gbps Direct Attach Fibre Channel connectivity for communication between all nodes in the local cluster. Clustering can also be accomplished with 25Gbps Ethernet, for standard topologies. For HyperSwap topologies a SCORE request will be required. Contact your IBM representative to raise a SCORE request.

Partnerships between systems for Metro Mirror or Global Mirror replication can be used with both Fibre Channel and native Ethernet connectivity. Distances greater than 300 metres are only supported when using an FCIP link or Fibre Channel between source and target.

Transparent Cloud Tiering
Transparent cloud tiering on the system is defined by configuration limitations and rules. Refer to the IBM Documentation maximum limits page for details.

The following restrictions apply for Transparent Cloud Tiering:

1. When a cloud account is created, it must continue to use the same encryption type, throughout the life of the data in that cloud account - even if the cloud account object is removed and remade on the system, the encryption type for that cloud account may not be changed while back up data for that system exists in the cloud provider.
2. When performing re-key operations on a system that has an encryption enabled cloud account, perform the commit operation immediately after the prepare operation. Remember to retain the previous system master key (on USB or in a key server) as this key may still be needed to retrieve your cloud backup data when performing a T4 recovery or an import.
3. Restore_uid option should not be used when backup is imported to a new cluster.
4. Import of TCT data is only supported from systems whose backup data was created at v7.8.0.1 or later.
5. Transparent cloud tiering uses Sig V2, when connecting to Amazon regions, and does not currently support regions that require Sig V4.

Encryption and TCT
There is an extremely small possibility that, on a system using both Encryption and Transparent Cloud Tiering, the system can enter a state where an encryption re-key operation is stuck in 'prepared' or 'prepare_failed' state, and a cloud account is stuck in 'offline' state.
The user will be unable to cancel or commit the encryption rekey, because the cloud account is offline. The user will be unable to remove the cloud account because an encryption rekey is in progress.
The system can only be recovered from this state using a T4 Recovery procedure.
It is also possible that SAS-attached storage arrays go offline.
There are two possible scenarios where this can happen:

Scenario A

1. Using USB encryption and Cloud;
2. A new USB key is prepared using chencryption -usb newkey -key prepare;
3. The new presumptive key is deleted from all USB sticks before the new key is committed;
4. All nodes in the system are rebooted;
5. The cloud account will now be offline as it can't get the presumptive key. The cloud account cannot be removed, and the encryption re-key cannot be completed or cancelled. The system will remain stuck in these cloud and encryption states;
6. Any SAS-attached arrays will be offline and locked;
7. The system can be restored by T4 to a previous config backup.

Scenario B

1. Using key server encryption and Cloud;
2. A new key server key is prepared using chencryption -keyserver newkey -key prepare;
3. The new presumptive key is deleted from the key server before the new key is committed;
4. All nodes in the system are rebooted;
5. The cloud account will now be offline as it can't get the presumptive key. The cloud account cannot be removed, and the encryption rekey cannot be completed or cancelled. The system will remain stuck in these cloud and encryption states;
6. SAS-attached arrays are not affected;
7. The system can be restored by T4 to a previous config backup.

NPIV (N_Port ID Virtualization)

The following recommendations and restrictions should be followed when implementing the NPIV feature.

FCoE is not supported with NPIV.

Operating systems not currently supported for use with NPIV:

• HPUX 11iV2
• Veritas DMP multipathing on Windows with RAID-5 volumes in VxVM

Other Operating Systems
Other operating Systems may also experience the same issue when changing the NPIV state from "Transitional" to "Disabled" in which case the operating system specific rescan command should be used.

Fabric Attachment
NPIV mode on SVC or Storwize is only supported when used with Brocade or Cisco Fibre Channel SAN switches which are NPIV capable.

Node Memory
Nodes in an I/O group cannot be replaced by nodes with less memory when compressed volumes are present

If a customer must migrate from 64GB to 32GB memory node canisters in an I/O group, they will have to remove all compressed volume copies in that I/O group.

A customer must not:

1. Create an I/O group with node canisters with 64GB of memory.
2. Create compressed volumes in that I/O group.
3. Delete both node canisters from the system with CLI or GUI.
4. Install new node canisters with 32GB of memory and add them to the configuration in the original I/O group with CLI or GUI.

HyperSwap
When using the HyperSwap function configure your host multipath driver to use an ALUA-based path policy.

Due to the requirement for multiple access IO groups, SAS attached host types are not supported with HyperSwap volumes.

A volume configured with multiple access I/O groups, on a system in the storage layer, cannot be virtualized by a system in the replication layer. This restriction prevents a HyperSwap volume on one system being virtualized by another.

AIX Live Partition Mobility (LPM)

AIX LPM is supported with the HyperSwap function and AIX 7.x

Direct Attachment
SAN Boot on Windows 2019 (Qlogic HBA) is not supported with 32GB direct-attached systems.

Fibre Channel Canister Connection
Visit the IBM System Storage Inter-operation Center (SSIC) for Fibre Channel configurations supported with node HBA hardware.

Auto-negotiation with 32, 16 and 8Gbps networks is supported.

Note 16Gbps Node hardware is supported when connected to Brocade and Cisco 8Gbps or 16Gbps fabrics only.

Direct connections to 2Gbps or 4Gbps SAN or direct host attachment to 2Gbps or 4Gbps ports is not supported.

Other configured switches which are not directly connected to node HBA hardware can be any supported fabric switch as currently listed in SSIC.

25Gbps Ethernet Canister Connection
Two optional 2-port 25Gbps Ethernet adapter is supported in each node canister for iSCSI communication with iSCSI capable Ethernet ports in hosts via Ethernet switches. These 2-port 25Gbps Ethernet adapters do not support FCoE.

There are two types of 25Gbps Ethernet adapter feature supported:

1. RDMA over Converged Ethernet (RoCE)
2. Internet Wide-area RDMA Protocol (iWARP)

Either will work for standard iSCSI communications, i.e. not using Remote Direct Memory Access (RDMA). A future software release will add (RDMA) links using new protocols that support RDMA such as NVMe over Ethernet.

When use of RDMA with a 25Gbps Ethernet adapter becomes possible then RDMA links will only work between RoCE ports or between iWARP ports.

i.e. from a RoCE node canister port to a RoCE port on a host or from an iWARP node canister port to an iWARP port on a host.

The 25Gbps adapters come with SFP28 fitted, which can be used to connect to switches using OM3 optical cables.

For Ethernet switches and adapters supported in hosts visit the SSIC .

This is an example of a RoCE adapter for use in a host.
https://docs.nvidia.com/networking/display/cx4lxen

This is an example of a iWARP adapter for use in a host.
https://www.chelsio.com/nic/unified-wire-adapters/t6225-cr/

IP Partnership
IP partnerships are supported on any of the available ethernet ports. Using an Ethernet switch to convert a 25Gb to a 1Gb IP partnership, or a 10Gb to a 1Gb IP partnership is not supported. Therefore the IP infrastructure on both partnership sites must match. Bandwidth limiting on IP partnerships between both sites is supported.

VMware vSphere Virtual Volumes (vVols)
The maximum number of Virtual Machines on a single VMware ESXi host in a Storwize / vVol storage configuration is limited to 680.

The use of VMware vSphere Virtual Volumes (vVols) on a system that is configured for HyperSwap is not currently supported with SVC/Storwize.

REST API
It is not possible to access the REST API using a cluster's IPv6 address.

Host Limitations

SAN BOOT function on AIX 7.2 TL5
SAN BOOT is not supported for AIX 7.2 TL5 when connected using the NVME/FC protocol.

RDM Volumes attached to guests in VMware 7.0
Using RDM (raw device mapping) volumes attached to any guest, with the RoCE iSER protocol, results in pathing issues or inability to boot the guest.

N2225/N2226 SAS HBA
VMware 6.7 (Guest O/S SLES12SP4) connected via SAS N2225/N2226 host adapters are not supported.

Lenovo 430-16e/8e SAS HBA
VMware 6.7 and 6.5 (Guest O/S SLES12SP4) connected via SAS Lenovo 430-16e/8e host adapters are not supported.
Windows 2019 and 2016 connected via SAS Lenovo 430-16e/8e host adapters are not supported.

Windows 2016 HyperV
RHEL v7.1 guests on Windows 2016 HyperV, with Virtual Fibre Channel, are not supported.

iSER
Operating systems not currently supported for use with iSER:

• Windows 2012 R2 using Mellanox ConnectX-4 Lx EN
• Windows 2016 using Mellanox ConnectX-4 Lx EN

Windows NTP server 
The Linux NTP client used by SAN Volume Controller may not always function correctly with Windows W32Time NTP Server

Fabric Limitations
Only one FCF ( Fibre Channel Forwarder ) switch per fabric is supported.

Storage connected directly to a Cisco Fabric Extender (FEX) is not supported.

Priority Flow Control for iSCSI/iSER
Priority Flow Control for iSCSI/ iSER is supported on Emulex & Chelsio adapters (SVC supported) with all DCBX enabled switches.

Maximum Configurations

Configuration limits for Storwize V7000:

Extents

The following table compares the maximum volume, MDisk and system capacity for each extent size.

* The total capacity values assumes that all of the storage pools in the system use the same extent size.
** See the following Flash