Troubleshooting
Problem
When a customer tries to increase the size of a JFS2 filesystem, he gets the error below: # chfs -a size=+1000G /mountpoint chfs: 0507-587 A JFS2 file system with a 4096-byte block size can not be larger than 68719476736 512-byte physical blocks.
Cause
Such an error is normally caused due to reaching the maximum filesystem size of 32 TB
Diagnosing The Problem
As a first step to verify the reason for the error message, we should run the command below against the filesystem to check the filesystem size:
# df -g /mountpoint
If the size reported is 32 TB or more, that means the filesystem reached the maximum filesystem size of 32 TB
Explanation of the error:
Many UNIX file systems only allocate contiguous disk space in units equal in size to the logical blocks used for the logical division of files and directories. These allocation units are typically referred to as disk blocks and a single disk block is used exclusively to store the data contained within a single logical block of a file or directory.
JFS2 supports multiple file system logical block sizes of 512, 1024, 2048, and 4096. The logical block size for a JFS2 is specified during its creation.
Here, that particular error means that the JFS2 filesystem that has its value for the logical block size as 4096-byte cannot be increased to larger than 68719476736 512-byte physical blocks.
If we do the math based on that, it will be like this:
68719476736 logical blocks × 512 bytes per physical block = 32 TB
Resolving The Problem
Unfortunately, there is no fix to such an error message as it goes beyond the limitations of the JFS2 filesystem size.
The following size limitations are recommended:
Item Description
Maximum JFS2 file system size: 32TB
Maximum JFS2 file size: 16TB
Minimum JFS2 file system size: 16MB
For more information on the topic, please read the contents of the links below:
JFS2 size limits
http://www.ibm.com/support/knowledgecenter/en/ssw_aix_61/com.ibm.aix.osdevice/jfs2sizelim.htm
JFS and JFS2 disk space segmentation
http://www.ibm.com/support/knowledgecenter/ssw_aix_61/com.ibm.aix.osdevice/diskspcseg.htm
JFS and JFS2 functions
http://www.ibm.com/support/knowledgecenter/ssw_aix_61/com.ibm.aix.osdevice/fs_jfs2.htm
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Document Information
Modified date:
17 June 2018
UID
isg3T1024285