User`s guide

Document Number: MAN-0057XX-000 Version 1.0
FAST
The FAST storage policy distributes access across all hard disks, also called striping (equivalent
to RAID 0). FAST presents the best data speed but no data redundancy. FAST storage policy
accelerates hard disk operating speed by using many disks in parallel. Hard drive data segments
are written to different disks simultaneously which increases performance while sacrificing data
redundancy.
To implement the FAST storage policy, the SteelVine Storage Processor creates a single virtual
volume that is striped across both hard drives, with a storage capacity that is equal to the sum of
both hard disk drives.
It is possible to set any node within a cascaded configuration to FAST, although there is no
performance benefit when using multiple layers of striping.
SteelVine
Drive A Drive B
Virtual FAST
volume
Port 0
Port 1
Capacity is Drive A
plus Drive B
Striping across disks
Figure 4 - FAST storage policy sample configuration
SAFE
The SAFE storage policy stores all data in duplicate on separate drives to protect against data
loss due to drive failure. One drive mirrors the other at all times, equivalent to RAID 1. Every
write operation goes to both drives. SAFE provides the highest level of data protection for
critical data that you cannot afford to lose if a hard drive fails, but halves the amount of storage
capacity because all data must be stored twice. The resulting storage capacity of the virtual
SAFE volume will be equivalent to the size of one hard drive (if both drives are the same) or the
smaller of the two drives (if they are different).
If one drive fails, the SAFE volume is still usable, but it is in a vulnerable state because its
mirrored hard drive is inaccessible. When the offline drive comes back online, the appliance
begins a rebuild process immediately to restore data redundancy. A message box appears in the
GUI to notify you that a rebuild is in progress.
Although the volume remains available during the rebuild process, the volume is susceptible to
data loss through damage to the remaining drive until redundancy is restored at the end of the
rebuild and verification process. Host access takes precedence over the rebuild process. If you
continue to use the SAFE volume during the rebuild, the rebuild process will take a longer time
to complete, and the host data transfer performance will also be affected.
57XX-Series SteelVine Manager User's Guide
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