ADIC 1.3 Manuale Utente

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With SNFX 1.3, a change has been 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. 

NOTE:

Due to allocation rounding, applications may still 
receive a premature 

out of space

 error, but 

only when there are only 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. This amount of reserved space is determined by the following 
formula: 

reserved space megabytes = (MaxConnections - 1) * 

MaxMBPerClientReserve * #-of-data-stripe-groups 

For example: 

1 TB file system, 4 data stripe groups, MaxConnections=25, 
MaxMBPerClientReserve=100 

After 

cvmkfs

 has been used to create the file system, 

df 

reports: 

File system    1K-blocks   Used             Available Use% Mounted on  snfs1
1073741824  9830400   1063911424      1%                       /snfs1 

While not recommended, the Reserved Extents feature can be disabled by 
applying the following setting to the Globals section of the FSM 
configuration file: 

MaxMBPerClientReserve 0 

This will cause the file system to not reserve space, but will reduce I/O 
performance in some cases.