Primary Storage

ZStack 3.10.0>Product Manuals>Maintenance Manual>Hardware>Primary Storage

A primary storage is a storage server used to store disk files, such as root volumes, data volumes, root volume snapshots, data volume snapshots, and image caches, for VM instances.

As shown in Primary Storage.

A primary storage can either be a local storage or a shared storage.

Local Storage: Use the hard disks of a host to store disk files.
Network Shared Storage: Support NFS, Shared Mount Point, Ceph, and Shared Block.
- NFS is a network file system storage.
- Shared Mount Point supports network shared storages provided by commonly used distributed file systems such as MooseFS, GlusterFS, OCFS2, and GFS2.
- Ceph uses distributed block storages.
- Shared Block uses shared block storages.

Scenario: Attaching Primary Storages to Clusters

The following are primary storages of the same type that a cluster can have:

A cluster can have one or more LocalStorage primary storages attached.
A cluster can have one or more NFS primary storages attached.
A cluster can have one or more Shared Block primary storages attached.
A cluster can have one Shared Mount Point primary storages attached.
A cluster can have only one Ceph primary storage attached.

The following are combinations of primary storages that a cluster can have:

A cluster can have both a LocalStorage and an NFS primary storage attached.
A cluster can have both a LocalStorage and a Shared Mount Point primary storage attached.
A cluster can have both a LocalStorage and a Shared Block primary storage attached.
A cluster can have both a Ceph and a Shared Block primary storage attached.
A cluster can have both a Ceph and more than one Shared Block primary storage attached.

Notice

When you use primary storages, note that:

LocalStorage, NFS, and Shared Mount Point primary storages are based on qcow2.
The consumption of the root volume and data volume of a VM instance is calculated by virtual capacity.
After a primary storage is disabled, the primary storage cannot be used to apply for new resources or create VM instances and data volumes. However, running VM instances will not be affected.
After a primary storage is maintained, the primary storage cannot be used to apply for new resources. In addition, existing running VM instances will also be stopped.
Relationship between primary storage and backup storage:
- LocalStorage, NFS, Shared Mount Point, Ceph, and Shared Block primary storages can work with ImageStore backup storages.
- LocalStorage, NFS, and Shared Mount Point primary storages can work with SFTP backup storages.
- Ceph primary storages can work with either ImageStore or Ceph backup storages.
Primary storages are used based on the thin provisioning mode. In addition, primary storages support overcommitting. When the overcommitment ratio is excessive large, pay attention to the usage of the actual physical capacity.
ZStack uses the virtual size to create volumes. If the virtual size is not enough to provide the required capacity, the volume will fail to be created.
Deleting a primary storage will also delete all the VM instances, volumes, and snapshots in the primary storage. Please exercise caution. The delete operation only removes the information about the primary storage, VM instances, volumes, and snapshots recorded in ZStack. Actual data will not be deleted.
You can set independent storage network and management network for shared storages. The management node judges the health status of VM instances based on the storage network. If no independent storage network exists, you can leave it unspecified, which means that the management network is used to judge the health status of VM instances.

Shared Block

Shared Block is a block-level data storage service that features simple deployment, flexible expansion, and high performance in comparison with SMP primary storage. Shared Block allows you to use a LUN device that you segmented on a SAN storage as a storage pool. This storage pool can be used by your appliance VM instances.

Shared Block adopts the shared block storage method to match ImageStore.
Shared Block allows you to add LUN devices online.

A cluster can have multiple Shared Block primary storages attached.
A cluster can have both one LocalStorage and one Shared Block primary storage attached.
Stopped VM instances can be migrated with volumes, except for shared volumes, across storages.
Primary storages support thin provision and thick provision modes.
- Thick provision: Allocate the required storage space in advance to provide sufficient storage capacities and to ensure storage performances.
- Thin provision: Allocate storage spaces as needed to achieve a higher storage utilization.
Live migrations can be performed on VM instances in Windows failover clusters.
Note: ZStack 3.9.0 and later versions provide specific support for Windows failover clusters. Due to this support, the live migration of VM instances will not have any adverse effects.

Notice

When you add a Shared Block primary storage, the Clear SharedBlock checkbox is not selected by default.
- If selected, the residual data in LUN devices will be forced to clean, including file systems, RAID, or signatures of partition tables.
- If your LUN devices store data, and you do not clean the devices, you will fail to add LUN devices or attach primary storages.
- When you add LUN devices, the devices must not include partitions. Or otherwise, you will fail to add the devices.

Primary Storage Maintenance (Advanced)

Shared Block Maintenance

Shared Block Capacity Expansion

To expand the capacity of the underlay FC SAN, follow these steps:

Before capacity expansion, confirm the best expansion plan with the storage vendor.
Make sure that the storage expansion does not affect the business, and then perform storage expansion.
After the storage expansion is finished, log in to the Cloud via the UI and refresh the capacity on the primary storage details page. The proper display of the capacity indicates that the storage expansion is completed.

Shared Block Maintenance

The planned maintenance of a primary storage will stop all VM instances on the primary storage. The administrator needs to migrate important VM instances in advance. The steps for planned maintenance of a primary storage are as follows:

Log in to ZStack via the UI. On the Primary Storage page, click Enter Maintenance to place the primary storage into maintenance mode.
Go to the backend of the primary storage to perform maintenance operations.
After the maintenance is completed, go to the Primary Storage page via the UI and click Start to start the maintenance of the primary storage.

Next Chapter:Backup Storage

Primary Storage

Scenario: Attaching Primary Storages to Clusters

Notice

Shared Block

Notice

Primary Storage Maintenance (Advanced)

Shared Block Maintenance

Shared Block Capacity Expansion

Shared Block Maintenance

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