Copyright@2014 D-Link System, Inc. All Rights Reserved.
47
D-Link Document – User Manual
TIP:
“Compression” options:
Disabled:
No compression at all. Default value.
Zero Reclaim:
When the data block contains all zeros, no physical space
will be consumed. The block will be marked specifically.
Generic Zero Reclaim:
It will reclaim data blocks with special patterns
such as all 0’s, all 1’s. Theoretically, it will have better storage efficiency.
Enabled:
This will always enable lossless data compression function using
LZJB algorithm.
TIP:
“Sync” means synchronous I/O, which is similar to the definition of write-
through. Synchronous I/O is that every file system transaction is written and
flushed to stable storage devices by a system call return. The application needs
to wait for the physical data update completion before it could issue another
command. Latency will be longer and performance will suffer.
If you don’t know how to use this setting, please leave it as default.
Disabled:
All write commands become asynchronous. It will ignore the
synchronous transaction demands of applications such as database or
NFS.
Standard:
The default value. It depends on the applications.
Always:
All write commands become synchronous even if the application
issues asynchronous transactions.
The “Sync” option will be unselectable if “volume” is selected instead of file
system. This is because synchronous write function is not supported in iSCSI
block access for the time being.
TIP:
“Number of data copies” in Create File System or Volume UI is used to create
mirroring of data to avoid data corruption. When the original file corrupts, the
system will use the extra “copy” to recover the corrupt file.
The value of two means that when you copy a 10MB file, it will take up 20MB
space. The value of three means that it will take up extra double space to store
the same data in the same storage pool.
Users will not be able to see the actual extra copies. They are controlled by the
file system.
Thin provisioning
The following are the thin provision features:
Dynamic allocating space to store user data.
Applied to both file system and volume.
Remove stranded or reserved-but-unused capacity. Improve storage efficiency.
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