This e-Learning module will explain several important concepts you should understand before working with volumes, including the different methods for creating volumes. This information applies to the Lenovo(R) Storage family of products.
A volume is a logical disk that the system presents to a host connected over a Fibre Channel or Ethernet network. Using volumes allows administrators to more efficiently manage storage resources. The external access to volumes follows the SCSI command set standard. Volumes also may be used as a copy target, in which case, a host would not access the volume.
A storage pool is a collection of managed disks that jointly contain all the data for a specified set of volumes. First, the system divides each managed disk in the pool into extents – storage blocks that are typically of equal size. Next, the administrator creates the volumes, a process that consumes the extents, and then maps them to the host objects. As a result, the system presents the volumes to the hosts.
Volumes are presented to hosts by host mapping, the process of controlling which hosts have access to specific volumes in the system. Administrators can create logical hosts using Fibre Channel, Fibre Channel over Ethernet, also known as FCoE, iSCSI, or SAS technology. Volumes can then be mapped to a host.
You have the ability to create different types of volumes, including generic, mirrored, thin-mirrored, and thin-provisioned. Your system might also allow for compressed volumes. Note that compressed volumes are not available on all Lenovo Storage products.
With mirrored volumes, there are two volume copies, and the host is only aware of the one logical volume. Mirrored volumes enable a volume to remain online if access to one of the volume copies is lost. Mirrored volumes are also used to create a copy of a volume, which can be compressed for space efficiency. To do this, you add a volume copy, and wait for the mirror to complete. Once the mirror is complete, delete the original, non-compressed volume.
When a host sees a volume with a storage space that is larger than the actual storage space that is allocated to the volume, you have a thin-provisioned volume. Thin-provisioned volumes are volumes with virtual storage that exceeds real storage. When additional real storage is required, you can manually or automatically expand the real storage.
You can use compressed volumes to help ensure efficient use of storage resources. A license is required to create compressed volumes. The management of compressed volumes is similar to the management of thin-provisioned volumes. The data is compressed when it is written to a volume, so that less real storage capacity is required. Compression can be used without interruption to other system processes.
As previously mentioned, compressed volumes are not available on all Lenovo Storage products.
After the volumes are created, you can specify which hosts can access the volumes.
Today, you learned about volumes and how they are created.
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