Posts

Showing posts from March, 2014

Swap space calculation | Unix / Linux:

Image
In general, * 2GB swap space for 4GB of RAM or less. * 4GB swap space for 4-16GB of RAM * 8GB swap space for 16-64GB of RAM * 16GB swap space for 64-256GB of RAM * 32GB swap space for 256-512GB of RAM But, Here is some-more detailed information about calculating swap space, Swap space can be a dedicated swap partition (recommended), a swap file, or a combination of swap partitions and swap files. Swap should equal 2x physical RAM for up to 2 GB of physical RAM, and then an additional 1x physical RAM for any amount above 2 GB, but never less than 32 MB. So, if: M = Amount of RAM in GB, and S = Amount of swap in GB, then Using this formula, a system with 2 GB of physical RAM would have 4 GB of swap, while one with 3 GB of physical RAM would have 5 GB of swap. Creating a large swap space partition can be especially helpful if you plan to upgrade your RAM at a later time. For systems with really large amounts of RAM (more than 32 GB) you can likely get away w

LINUX - Detailed history of the commands:

Through ' history ' command, We can see what are all the commands used before, Normal 'history' command output: #  history     1  ls     2  cd /     3  cd     4  cd /var/log/     5  cd ..     6  cd /     7  cd     8  history Can we get more / exact details about when the commands were performed ? Yes, we can get more information by usgin " export HISTTIMEFORMAT='%F %T ' " After performing " export HISTTIMEFORMAT='%F %T ' ", the output goes like, # export HISTTIMEFORMAT='%F %T ' # history     1  2014-03-07 07:11:57 ls     2  2014-03-07 07:12:00 cd /     3  2014-03-07 07:12:01 cd     4  2014-03-07 07:12:18 cd /var/log/     5  2014-03-07 07:12:21 cd ..     6  2014-03-07 07:12:24 cd /     7  2014-03-07 07:12:25 cd     8  2014-03-07 07:12:28 history     9  2014-03-07 07:13:31 export HISTTIMEFORMAT='%F %T'    10  2014-03-07 07:13:3 4history Cheers !!!

measuring exact IO wait:LINUX

iostat - Report Central Processing Unit (CPU) statistics and input/output statistics for devices and partitions. We can get detailed report from iostat with N for LABEL. # iostat -xN 1 Device:         rrqm/s   wrqm/s     r/s     w/s   rsec/s   wsec/s avgrq-sz avgqu-sz   await  svctm  %util sda               0.00     4.00   51.00    2.00 11640.00    48.00   220.53     0.08    1.49   1.42   7.50 zz_root     0.00     0.00    2.00    6.00    48.00    48.00    12.00     0.00    0.00   0.00   0.00 yyy_swap     0.00     0.00    0.00    0.00     0.00     0.00     0.00     0.00    0.00   0.00   0.00 xxxxx_home     0.00     0.00   49.00    0.00 11592.00     0.00   236.57     0.08    1.61   1.53   7.50 fuser : command lists the process numbers of local processes that use the local or remote files specified by the File parameter. -v        verbose output -m        show all processes using the named filesystems # fuser -vm xxxxx_home