Viewing Pool and Device Status (BUI)
Data Profile Description
lower random read capability than mirrored options.
Single parity RAID can be considered for non-critical
applications with a moderate random read component.
For pure streaming workloads, give preference to the
Double parity RAID option which has higher capacity
and more throughput.
Other
Striped Data is striped across disks, with no redundancy. While
this maximizes both performance and capacity, a single
disk failure will result in data loss. This configuration
is not recommended. For pure streaming workloads,
consider using Double parity RAID. Due to non-
redundancy, disks configured in a striped profile will not
receive firmware updates, unless the configured storage
pools are in an exported state.
Triple parity RAID, wide stripes RAID in which each stripe has three disks for parity.
This is the highest capacity option apart from Striped
Data. Resilvering data after one or more drive failures
can take significantly longer due to the wide stripes
and low random I/O performance. As with other RAID
configurations, the presence of cache can mitigate the
effects on read performance. This configuration is not
generally recommended.
Note - Earlier software versions supported double parity with wide stripes. This has been
supplanted by triple parity with wide stripes, as it adds significantly better reliability. Pools
configured as double parity with wide stripes under a previous software version continue to be
supported, but newly-configured or reconfigured pools cannot select that option.
For expandable systems, some profiles may be available with an 'NSPF' option. This stands for
'no single point of failure' and indicates that data is arranged in mirrors or RAID stripes such
that a pathological disk shelf failure will not result in data loss. Note that systems are already
configured with redundancy across nearly all components. Each disk shelf has redundant paths,
redundant controllers, and redundant power supplies and fans. The only failure that NSPF
protects against is disk backplane failure (a mostly passive component), or gross administrative
misconduct (detaching both paths to one disk shelf). In general, adopting NSPF will result in
lower capacity, as it has more stringent requirements on stripe width.
Log devices can be configured using only striped or mirrored profiles. Log devices are only
used in the event of node failure. For data to be lost with unmirrored logs, it is necessary
for both the device to fail and the node to reboot immediately after. This a highly-unlikely
event, however mirroring log devices can make this effectively impossible, requiring two
simultaneous device failures and node failure within a very small time window.
112 Oracle ZFS Storage Appliance Administration Guide, Release OS8.6.x • September 2016
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