IBM Storwize V5010 Manual page 845

Data reduction pool
Data Reduction pools are specific types of pools where more control over volumes capacity is
given to specific hosts (for example VMware VAAI/VASA/VVOL, Microsoft ODX). These hosts
are able to return unused space for reuse. With standard pools, the system is not aware of
any unused space on host-allocated volumes.
Dependent write operation
A write operation that must be applied in the correct order to maintain cross-volume
consistency.
Directed Maintenance Procedure
The fix procedures, which are also known as Directed Maintenance Procedures (DMPs),
ensure that you fix any outstanding errors in the error log. To fix errors, from the Monitoring
panel, click Events. The Next Recommended Action is displayed at the top of the Events
window. Select Run This Fix Procedure and follow the instructions.
Discovery
The automatic detection of a network topology change, for example, new and deleted nodes
or links.
Disk tier
MDisks (logical unit numbers (LUNs)) that are presented to the IBM Storwize V5000 likely
have different performance attributes because of the type of disk or RAID array on which they
are installed. MDisks can be on 15,000 revolutions per minute (RPM) Fibre Channel (FC) or
serial-attached SCSI (SAS) disk, Nearline SAS, or Serial Advanced Technology Attachment
(SATA), or even Flash Disks. Therefore, a storage tier attribute is assigned to each MDisk,
generic_hdd
and the default is .
Distributed RAID or DRAID
An alternative RAID scheme where the number of drives that are used to store the array can
be greater than the equivalent, typical RAID scheme. The same data stripes are distributed
across a greater number of drives, which increases the opportunity for parallel I/O and hence
improves overall array performance. See also "Rebuild area" on page 831.
Easy Tier
Easy Tier is a volume performance function within the IBM Storwize family that provides
automatic data placement of a volume's extents in a multitiered storage pool. The pool
normally contains a mix of Flash Disks and HDDs. Easy Tier measures host I/O activity on
the volume's extents and migrates hot extents onto the Flash Disks to ensure the maximum
performance.
Encryption key
The encryption key, also known as master access key, is created and stored on USB flash
drives or on a key server when encryption is enabled. The master access key is used to
decrypt the data encryption key.
Encryption key server
An internal or external system that receives and then serves existing encryption keys or
certificates to a storage system.
823
Appendix B. Terminology