Dell PowerVault ME4 Series Storage System Administrator’s Guide

Expanding a disk group

You can expand the capacity of a linear disk group, or a virtual disk group with a RAID level set to ADAPT up to the maximum number of disks that the storage system supports. Host I/O to the disk group can continue while the expansion proceeds. You can then create or expand a volume to use the new free space that becomes available when the expansion is complete. As described in About RAID levels, the RAID level determines whether the disk group can be expanded and the maximum number of disks the disk group can have. This task cannot be performed on an NRAID or RAID-1 disk group.

The following table summarizes disk group types that can be expanded.

When expanding a disk group, all disks in the disk group must be the same type (enterprise SAS, for example). Disk groups support a mix of 512n and 512e disks. However, for best performance, all disks should use the same sector format. For more information about disk groups, see About disk groups.

Before expanding non-ADAPT disk groups, back up the data for the disk group so that if you need to stop expansion and delete the disk group, you can move the data into a new, larger disk group.

When disks are added to an ADAPT disk group, the system will first replenish any spare capacity needed to be fully fault-tolerant, then use the remainder for expansion of user data capacity. When set to the default spare capacity, the system will try to replenish spare capacity to be the sum of the largest two disks in the group.

• When default spare capacity has been overridden the system will try to replenish spare capacity to meet the configured target GiB. For more information, see the topic about the add disk-group command in the Dell PowerVault ME4 Series Storage System CLI Guide.
• If the actual spare capacity meets the target spare capacity, the new disk capacity will be allocated to user data. For information on how ADAPT disk groups manage sparing, see About RAID levels.

There are three sections that comprise the Expand Disk Group panel. The top section displays information about the disk group, including its name, type, owner (controller), and data protection (RAID) level. The information that is based on the type of disk group being expanded.

The middle section contains the disk selection sets summary and Disks table which presents cumulative data for existing disks and dedicated spares in the disk group as well as for selected disks. The amount of disk space is color-coded to show total, available, dedicated spares, and overhead disk space amounts.

The Disks table lists information about the disks and dedicated spares in the disk group, updating as you select disks to expand the disk group to show the total number of disks selected and the total size of the disk group.

The bottom section lists the disks in each enclosure in your system, along with their details. Select the disks that you want to add to the current disk group by doing one of the following:

• Select a range of disks within an enclosure by entering a comma-separated list that contains the enclosure number and disk range in the Enter Range of Disks text box. Use the format enclosure-number.disk-range,enclosure-number.disk-range. For example, to select disks 3-12 in enclosure 1 and 5-23 in enclosure 2, enter 1.3-12,2.5-23.
• Select all disks by checking the Select All checkbox.
• Filter the disks in the list per disk description, enclosure ID, slot location, or disk size by entering applicable search criteria in the text box. Clear the filter by clicking the Clear Filters button.
• Click on individual disks within the table to select them and add them to the disk group.

Selected disks are highlighted in blue. To remove disks from the group, click on them the disks to deselect them.