Sample set of parameters - Solaris I/O - UFS Tuning

Some of I/O related /etc/system parameters are listed below, This system is a 32GB Solrais x86 server, Always refer to the "SolarisTunable Parameters ReferenceManual" before applying to the systems.

• set maxusers=2048 <- Number of concurrent users on the system determining the amount of physical memory allocated to the kernel (lot of memory and relatively few running processes can save system memory when the default value of maxusers is reduced)
• set ncsize=12000000 <- Defines the number of entries in the directory name look-up cache(DNLC) , use the kstat -n dnlcstats command to determine when entries have been removed from theDNLC because it was too small
• set maxphys=8388608 <- the maximum size of physical I/O requests. If a driver encounters a request larger than this size, the driver breaks the request into maxphys sized chunks
• set pt_cnt=4096 <- When you want to explicitly control the number of users who can remotely log in to the system.
• set npty=176 <- npty limits the number of BSD ptys
• set sadcnt=8192 <- nautopush should be set to twice sadcnt
• set nautopush=4096 <- Set to twice the value of pt_cnt
• set rlim_fd_max=1048576 <- Hard limit on the open file descripters for a single process
• set autoup=600 <- Controls the frequency in seconds of entire physical memory to be scanned for dirty pages
• set tune_t_fsflushr=1 <-Reduces fsflush daemon overhead
• set ufs <-ufs_HW=67108864 <- Limit the amount of I/O that may be outstanding to a single file on a system-wide basis
• set ufs <-ufs_LW=4194304 <- When ufs_HW bytes are outstanding, I/O requests will sleep until less than ufs_LW bytes are outstanding
• set rlim_fd_cur=524288 <- the "soft" limit on file descriptors that a single process can have open
• set segspt_minfree=12500 <- Identifies pages of system memory that cannot be allocated for ISM shared memory
• set maxpgio=65536 <-maximum number of page I/O requests that can be queued by the paging system
• set fastscan=65536 <- maximum number of pages per second that the system looks at when memory pressure is highest
• set segmap_percent=32 <- Amount of memory used, to hold file system pages, % from the physical memory