Veritas File System 5.0 Release Notes (September 2006)

Veritas File System 5.0 Release Notes
Known Issues
Chapter 118
Known Issues
• Applications using statvfsdev (3C) interface
The applications that use the statvfsdev (3C) interface on a device name need to relink with the new
LIBC to be able to understand the Disk Layout Version 6 and 7. If the applications are not relinked, they
cannot recognize a file system with Disk Layout Version 6 or Disk Layout Version 7. However, they
would continue to recognize file systems with Disk Layout Version 4 and 5.
• Large file support
VxFS 5.0 only supports files up to 2 TB on 64-bit kernels.
• Mapping a large offset of a file
Calling the mmap (2) function on a large offset of a file might require a large amount of swap space. If
mmap (2) is called on a 1 TB offset in MAP_SHARED mode, then approximately 256 MB of virtual
memory pages could be instantiated. This means that VM requires space to hold 256 MB of data
structures. Each of these structures are 16 bytes, thus approximately 4 GB space is required. Since these
data structures are able to be paged, more than 4 GB of swap space is reserved when mmap (2) is called.
• System hang can occur on systems with less cache memory
VxFS allocates a fixed amount of memory. You can change the amount of memory allocated using the
tunables vx_ninode and vxfs_bc_bufhwm. After long hours of operation, low-memory systems
(that is, systems having less physical RAM), may slow down or hang due to memory pressure. To
alleviate this problem, lower the values of vx_ninode and vxfs_bc_bufhwm to limit VxFS memory
consumption.
NOTE VxFS consumes a fixed percentage of memory for storing the default values of
tunables, such as vx_ninode and vxfs_bc_bufhwm. For example, VxFS consumes
nearly 10% of total physical memory for the default value of vx_ninode. If the
system has 512 MB of memory, VxFS will require up to 52 MB to store the VxFS
inode cache. Therefore it is necessary to tune the tunables according to the type of load
on the system.
• Tuning down the inode cache
VxFS allocates and releases inodes based on the file system load. Generally, larger inode caches help
the file system to perform better in the case of a file server or web server load. The global tunable,
vx_ninode, determines the maximum possible size of the VxFS inode cache. If the default value of
vx_ninode is set to zero, VxFS automatically tunes the size of the inode cache at boot time, based on