Veritas File System 4.1 Release Notes (5900-0592, March 2010)

The vx_hsm_get_dirattr() reads a directory entry 8 KB at a time. If the user buffer is
not large enough to hold the combined entries of the corresponding file statistics information
(up to ~114kb), the next call to vx_hsm_get_dirattr () will continue from the wrong
offset within the directory, resulting in some directory entries being skipped.
No error is displayed and the processing continues from the last directory entry information
that can be fitted into the user buffer. However, the next directory read will begin 8 KB
further down the directory.
Workaround
The buffer size must be sufficiently large.
• Large Files Should Be Mounted Only on Systems With Sufficient Memory
When a file system is mounted, VxFS creates some additional data structures in the kernel.
As the size of the file system increases, the amount of data structures stored by VxFS also
increases. The file system stores upto 128 bytes per allocation unit (32,768 file system blocks).
This translates to a usage of 512K per 1 TB for an 8K block size file system (4 MB per 1 TB
for a 1K block size file system). Therefore, large file systems must be mounted only on
systems that have sufficient memory. The memory requirements for mounting large file
systems are shown in the tables below.
Table 1-4 Memory Usage for a File System With a 1K Block Size
256 TB64TB8 TB1 TB128 GB
File System
Size
N/AN/A32 MB4 MB1 MBMemory
Usage
Table 1-5 Memory Usage for a File System With a 2K Block Size
256 TB64TB8 TB1 TB128 GB
File System
Size
N/A128 MB16 MB2 MB512 KMemory
Usage
Table 1-6 Memory Usage for a File System With a 4K Block Size
256 TB64TB8 TB1 TB128 GB
File System
Size
N/A64 MB8 MB1 MB256 KMemory
Usage
Table 1-7 Memory Usage for a File System With a 8 K Block Size
256 TB64TB8 TB1 TB128 GB
File System
Size
128 MB32 MB4 MB512 KB128 KBMemory
Usage
• While performing a full fsck, the system keeps certain data structures in the core for
validating the space usage and inode usage. The space needed depends on the number of
inodes and the number of blocks in the file system. The fsck command needs approximately
16 MB per 1 TB for an 8K block size file system (128 MB per 1 TB for a 1K block size file
system) and 32 MB per million inodes. Sufficient memory and swap space should be
configured on the system before running a full fsck on a large file-enabled system.
A replay fsck does not need a significant amount of memory and does not have these
issues.
14 Veritas File System 4.1 Release Notes