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Space Management for Shares
Space Management for Shares
The Oracle ZFS Storage Appliance manages physical storage using a pooled storage model
where all filesystems and LUNs share common space. Filesystems never have an explicit size
assigned to them, and only take up as much space as they need. LUNs reserve enough physical
space to write the entire contents of the device, unless they are thinly provisioned, in which case
they behave like filesystems and use only the amount of space physically consumed by data.
This system provides maximum flexibility and simplicity of management in an environment
when users are generally trusted to do the right thing. A stricter environment, where user's data
usage is monitored and/or restricted, requires more careful management.
These topics define terminology and how to manage space usage, on a per-share or per-user
basis, using quotas and reservations.
"Shares Terminology" on page 396
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"Managing Filesystem and Project Space" on page 397
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"Setting User or Group Quotas" on page 398
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"Working with Identity Management" on page 399
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"Share Usage Statistics" on page 401
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Shares Terminology
Before getting into details, it is important to understand some basic terms used when talking
about space usage on the appliance.
Physical Data - Size of data as stored physically on disk. Typically, this is equivalent to
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the logical size of the corresponding data, but can be different in the phase of compression
or other factors. This includes the space of the active share as well as all snapshots. Space
accounting is generally enforced and managed based on physical space.
Logical Data - The amount of space logically consumed by a filesystem. This does not
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factor into compression, and can be viewed as the theoretical upper bound on the amount
of space consumed by the filesystem. Copying the filesystem to another appliance using
a different compression algorithm will not consume more than this amount. This statistic
is not explicitly exported and can generally only be computed by taking the amount of
physical space consumed and multiplying by the current compression ratio.
Referenced Data - This represents the total amount of space referenced by the active
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share, independent of any snapshots. This is the amount of space that the share would
consume should all snapshots be destroyed. This is also the amount of data that is directly
manageable by the user over the data protocols.
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Oracle ZFS Storage Appliance Administration Guide, Release OS8.6.x • September 2016
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