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VSCSI - Storage pools

In Virtual I/O Server (VIOS) Version 1.5, and later, you can create the following types of storage pools:

    * Logical volume storage pools (LVPOOL)
    * File storage pools (FBPOOL)

Like volume groups, logical volume storage pools are collections of one or more physical volumes. File storage pools are created within a parent logical volume storage pool and contain a logical volume containing a file system with files.

Logical volume storage pools store logical volume backing devices, file-backed storage pools, and the virtual media repository. File storage pools store file-backing devices.

In VIOS Version 2.2.0.11, Fix Pack 24, Service Pack 1, or later, you can use shared storage pools. Shared storage pools provide distributed storage access to all VIOS logical partitions in a cluster. Each cluster consists of one VIOS logical partition.

Storage pools are created and managed using the following commands:
chsp         Changes the characteristics of a storage pool
chbdsp       Changes the characteristics of a backing device within a storage pool
lssp         Displays information about a storage pool
mkbdsp       Assigns storage from a storage pool to be a backing device for a virtual SCSI adapter
mksp         Creates a storage pool
rmbdsp       Removes a backing device from its virtual SCSI adapter, and returns the storage back to the storage pool.
rmsp         Removes a file storage pool

By default, rootvg, which is a logical volume pool, is the default storage pool unless the prime administrator configures a different default storage pool.

Storage pools cannot be used when you assign whole physical volumes as backing devices:


When using file-backed virtual SCSI disks, you define storage-pool resources on the VIOS to contain the files that will serve as client disks.
When defining file-backed virtual disks, first use the mksp or mkvg command from the VIOS command-line interface to define a logical volume (LV) storage pool on the VIOS. An LV storage pool is a volume group in AIX LVM.

The next step in providing file-backed virtual disks is creating file-backed storage pools (or AIX LVs). You must use the mksp -fb command from the VIOS command line to create file-backed storage pools, and it doesn’t allow you to control placement of logical volumes in the volume group.

Once you create a file-backed storage pool, create a file-backed virtual disk for a client. Using the mkbdsp command, you create a file the client will use, and the virtual target device that links it to a virtual SCSI server adapter in the VIOS in one step.

The client attached to the server adapter will access the file on the VIOS as a SCSI disk. However, since the access is to a file that may be placed across multiple disks in the VIOS, you may see performance gains. Additionally, because it’s possible to create multiple file-backed disks in a single file-backed storage pool, there’s more flexibility available with this type of virtual SCSI disk than when using physical or logical volumes.

Performance gains are available when file-backed storage pools are defined across multiple physical volumes in a volume group (LV storage pool). For this reason, it’s recommended LV storage pools are defined across multiple physical volumes when possible.

However when we plan to use logical volumes as backing devices (not file-baked disks) keep this in mind:
Although logical volumes that span multiple physical volumes are supported, a logical volume should reside wholly on a single physical volume for optimum performance. To guarantee this, volume groups can be composed of single physical volumes.


4 comments:

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  2. Hi, thank so much for the post, can anyone explain
    How is this better then the Current way using of VSCSI or NPIV, thank you

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    1. Hi, as far as I know, from performance point of view, there is no difference, so you can choose which one fits better to your environment. (I think having rootvg on vscsi and datavg on npiv could be a good solution...)

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