VERITAS File System 3.5 (HP OnlineJFS/JFS 3.5) Release Notes (5971-4774, August 2003)

VERITAS File System 3.5 (HP OnlineJFS/JFS 3.5) Release Notes
Known Issues
Chapter 1
11
Known Issues
• Non-pingable hang on low memory systems
VxFS may cause a hang on low memory systems after long hours of operation.
You can address the known issue of non-pingable hang by allocating appropriate
memory for the tunables, vx_ninode and vx_bc_bufhwm.
NOTE VxFS consumes a fixed percentage of memory for storing the default values of tunables
such as vx_ninode and vx_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. Hence it is
necessary to tune the tunables according to the type of load on the system.
Tuning down the
inode cache
VxFS file systems allocate and release inodes based on the file system load. Generally,
larger inode caches help the file systems to perform better in case of a file server or web
server load. The global (static) 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 the size of the
physical memory on the system. On systems with a RAM size of less than or equal to
1GB per CPU, you can manually tune down vx_ninode to a value not less than that of
nfile (nfile is an HP-UX tunable that represents the maximum number of file
descriptors).
Tuning down the
buffer cache
VxFS 3.5 implements a private buffer cache to use exclusively for meta data. The
allocations to this buffer cache vary during system usage, based on file system load and
the maximum cache size specified in the global (static) tunable, vx_bc_bufhwm. If the
value of vx_bc_bufhwm is set to zero, VxFS automatically tunes the maximum size of
the meta data buffer cache at boot time, based on the system memory size. On systems
with a RAM size of 1GB per CPU or less, you can manually tune down the value of
vx_bc_bufhwm to a minimum of 6144 (6MB).
Known Limitations
VxFS poses a limitation on the maximum number of inodes for
a 32-bit fsck, kernel parameter setting, system memory size,
and swap size. For information on these limitations, see
the Veritas File System 3.5 Administrator's Guide.