Dell Compellent Series 30 - Manual (Page 33)

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Introduction
Step 6. Monitor Alerts - Ongoing
Add Space as Required
Disk drives that are managed by the Storage Center are contained in a disk folder, which
is simply a logical grouping of physical drives. Disk folders can contain a mixture of drive
types, capacities, and speeds. The total capacity of the disk folder is the sum of the
capacities of the drives within the folder. Disk folders also contain disk drives that are
specified as hot spares. Hot spare drives are reserved for use as replacement drives in the
event another disk in the disk folder fails. Since the space on these hot spares is never used
until another drive fails, their capacity is not included in the total capacity for the disk folder.
Storage Center allocates disk space from a disk folder for volume and Replay use as
needed based upon the configurations and IO patterns of each volume. As the Storage
Center approaches the end of the disk space available within the disk folder, it will generate
an alert, warning you to add additional space.
Conservation Mode
Storage Center enters Conservation Mode when remaining free space reaches 32 GB (or
less for systems smaller than 3.2 TB). When Storage Center enters conservation mode, the
system generates a Conservation Mode Alert to inform you that the system will not allow
new volumes to be created and that it will begin to aggressively expire Replays. The
Conservation Alert is close to the boundary where space is exhausted to keep these
actions from being performed unless necessary. Because of its proximity to the emergency
threshold, it is not a tool to manage storage, and should not be used to plan adding
additional disks to the system.
Emergency Mode
Emergency threshold means that the system can no longer operate because there is no
more free space. Storage Center:
• Generates an emergency alert
• Expires Replays early
• Will not permit new volumes to be created
• All volumes are taken offline
When Storage Center reaches the Emergency threshold, all server IO is rejected until the
system gets out of Emergency Mode. Because this is service affecting, special care should
be taken to monitor free space on the system to avoid reaching this threshold. Volumes will
not be able to be brought back online until enough space is freed to exit the emergency
state. Before a system reaches Emergency Mode, it is critical that you add space. Refer to
Conservation Mode on page 25 .
Monitor Physical Components
Alerts warn you of component failure when the Storage Center requires attention. The
status of the Storage Center is indicated by the color of the System Status icon in the top-
right corner of the System Manager.
• Red (Critical) The System Status icon appears red when an alert exists that has a status
of Down, Critical, or Emergency. When the System Status icon is red, this indicates a
condition that requires immediate attention.