HP StorageWorks Scalable File Share System Installation and Upgrade Guide Version 2.2

Configuring EVA4000 storage 5–17
5.2.5.4 Step 4: Creating virtual disks
The size of the virtual disks that you can create depends on a number of factors, including the following:
• Capacity of the disk group
You cannot allocate more than 90% of the total capacity of the disk group, and the Command View
EVA Web interface enforces this rule. For example, if the disk group has a total capacity of 350GB,
the maximum size for a virtual disk in the disk group is 315GB (that is, 90% of 350GB).
• Redundancy level
In an HP SFS system, you must use the RAID5 redundancy level on EVA4000 arrays. The overhead
required to support this level of redundancy reduces the available capacity by a further 20%. For
example, in a disk group where the available capacity is 315GB, using RAID5 redundancy reduces
the available capacity to 252GB. The Command View EVA Web interface shows the capacity that is
available given the RAID5 overhead.
• Number of virtual disks being created in the disk group
For example, you may be creating two virtual disks in a disk group, one to be used as a service LUN,
and a second to be used as an OST LUN. The service LUN must be 1GB in size, and this reduces the
capacity available for the OST LUN accordingly.
When creating virtual disks, note the following points:
• On EVA4000 arrays that are assigned to the administration and MDS servers
2
, you must create
virtual disks as follows:
• Create one virtual disk for use as an administration LUN for the entire system.
• For each file system that you plan to create, create two virtual disks for use as MDS LUNs. For
example, if you plan to have two file systems, you must create four MDS LUNs.
• Create one virtual disk for use as a service LUN for the administration and MDS server pair.
• If OST services are run on the administration and MDS servers, create two virtual disks on each
of the arrays for use as OST LUNs.
• On EVA4000 arrays that are assigned to Object Storage Server pairs, you must create virtual disks
as follows:
• Create one virtual disk for use as a service LUN for the Object Storage Server pair.
This virtual disk can be on either of the EVA4000 arrays that are assigned to the Object Storage
Server pair.
• On each of the arrays, create two virtual disks for use as OST LUNs.
Create the virtual disks, as follows:
1. In the Navigation pane, select the Virtual Disks entry, then click the Create Vdisk button on the
Content pane.
2. On the Create a Vdisk Family page, enter the information for the virtual disk. Do not assign numbers
to the virtual disks that are to be used as OST LUNs; LUN numbers will be assigned when you
configure file systems.
Figure 5-4 shows the Create a Vdisk Family page with the information for a virtual disk called ostA.
2. In a typical system, there is one dedicated EVA4000 array for the administration and MDS server pair.
On smaller systems where OST services are run on the administration and MDS servers, two EVA4000 arrays are assigned to the
administration and MDS server pair. In this case, the virtual disk that is to be used as the administration LUN must be created on the
array that will normally be accessed by the administration server. The MDS LUNs must be created on the array that will normally be
accessed by the MDS server.