VERITAS Storage Foundation 4.1 Release Notes

Software Issues
40 VERITAS Storage Foundation Release Notes
VERITAS File System Software 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. Disk Layout Version 6 is available
with this release. If the applications are not relinked, they cannot recognize a file system with disk
layout Version 6. However, they would continue to recognize file systems with disk layout Version
4 and 5.
Large File Support
VxFS 4.1 only supports files up to 2 TB on 64-bit kernels. See related issue “Large File Systems
and Large File Support” on page 15 for more information.
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.