Quantum 3.5.1 Benutzerhandbuch

General Operating Guidelines and Limitations

StorNext User’s Guide

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As of SNFS 2.7, a change was made to the way that the Reserved Extents 

performance feature affects free space reporting. In the previous release, 

SNFS would reserve a certain amount of disk space which would cause 

applications to receive an 

out of space

 error before the disk capacity reached 

100%. 
In the current release, this reserved space is treated as allocated space. This 

allows applications to perform allocations until the file system is nearly full. 

 Due to allocation rounding, applications may still receive a premature 

out of space

 error, but only when there are just a few megabytes of space 

remaining. In the worst case, the error will be returned when the reported 

remaining space is: 

(InodeExpandMax * #-of-data-stripe-groups)

 

One side effect of this change is that after creating a new file system, 

df 

will 

show that space has been used, even though no user data has been allocated.
The amount of reserved space varies according to client use but does not go 

below a “floor” of a few gigabytes per data stripe group. The amount of 

reserved space at any time can be seen using the 

cvadmin

 command, selecting 

the file system, and using show long.
While not recommended, the Reserved Extents feature can be disabled by 

applying the following setting to the Globals section of the FSM 

configuration file: 

ReservedSpace No 

This will cause the file system to not reserve space for buffered I/O, thereby 

reducing buffer cache performance and possibly causing severe 

fragmentation.
For more information, see 

the 

cvfs_config(4) man

 page.