The SAFE33 storage policy creates two virtual volumes; one SAFE volume and one BIG
volume, and should be used when you need the high reliability for some of your data (with the
added overhead of mirroring) but you don’t need high reliability for the remainder of your data.
SAFE33 reduces the cost of additional hard drives in operations where non-critical data could be
lost without severe consequences.
SAFE33 uses a SAFE volume that is mirrored across two hard drives to protect your critical data
in the event a hard drive failure. If one drive fails the SAFE volume is retrievable although the
BIG volume is not. When you replace the failed drive, the SAFE volume is automatically rebuilt
on to the replacement drive.
For example, if you are using a video editing application that stores the primary source data and
also uses some temporary storage for editing, you need protected storage that is offered by SAFE
for the primary source data, but you do not need protected storage for the temporary data.
Therefore, the combination of SAFE and BIG would be the most efficient utilization of your
available storage capacity. If either hard drive fails the primary data stored on the SAFE volume
would still be available whereas the temporary data stored on the BIG volume would be lost.
The size of the SAFE volume of a SAFE33 policy will be one-third of the size of one hard drive
(if they are equal) or one-third of the size of the
smaller (if they are not equal.
) The size of the
BIG volume will be the combination of all remaining capacities.
Example: In Figure 6 below, assume that Drives A and B are 300 GB each. When the SAFE33 Storage
Policy is selected, the resulting virtual volumes will include SAFE volume of 100 GB (1/3 of 300 GB) and
a BIG volume of 400 GB (the remaining capacity after allocating 100 GB from each of the hard drives).
Figure 6 - SAFE33 storage policy sample configuration
When using a SATA host connection, you must have a PM (Port Multiplier) aware host adapter
when using SAFE33 on the top level node of a cascaded configuration so that ALL volumes can
be detected by the host. If your SATA host adaptor is not PM aware, then ONLY the SAFE
volume will be detected and the BIG volume will not be accessible. No such limitation exists
when using a USB host connection.
For subordinate nodes in a cascaded configuration, it is possible to configure a SAFE33 storage
policy, although you will only see the SAFE volume from that node. Therefore, the SAFE33
storage policy should only be used at the top-level node of a cascaded configuration.
Refer to the
Capacity Expansion for SAFE33 & SAFE50
section below for additional
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