Factors for Disk Performance


 

 

df -k command


 

How to use df

 

#> df

 

How to read df output

 

%capacity = 100%

 

Example of df

 

#> df -k
Filesytem         kbytes   used avail capacity Mounted on
/dev/dsk/c0t3d0s0  21615  14909  4546      77% /
/dev/dsk/c0t3d0s6 240463 211348  5075      98% /usr
/proc                  0      0     0       0% /proc
 

 

iostat command


 

How to use iostat

 

#> iostat 5

#> iostat -x 5

 

How to read iostat -x output

 

%b

svc_t

 

iostat -D command


 

How to use iostat -D

 

#> iostat -D 5

 

Example of iostat

 

#> iostat 5
     tty          fd0          sd0          sd1          sd2         cpu
tin tout Kps tps serv Kps tps serv Kps tps serv Kps tps serv us sy wt id
  0  560   0   0    0   0   0   99   1   0   49  10   2   54  4  4  4 88
  0   16   0   0    0   0   0    0   0   0    0   0   0    0  0  0  0 99

#> iostat -x 5
                    extended disk statistics
disk r/s w/s Kr/s Kw/s wait actv svc_t %w %b
fd0  0.0 0.0  0.0  0.0  0.0  0.0   0.0  0  0
sd0  0.0 0.0  0.2  0.1  0.0  0.0  99.5  0  0

#> iostat -D
         fd0          sd0          sd1          sd2
rps wps util rps wps util rps wps util rps wps util
  0   0  0.0   0   0  0.2   0   0  0.4   1   0  3.1

 

sar -a -b -d command


 

How to use sar

 

#> sar -a 5 3

#> sar -b 5 3

#> sar -d 5 3

 

How to read sar data

 

sar -a

The large the values, the more time the kernel is spending to ACCESS user files

This report is USEFUL for understanding "HOW disk-dependent a system is"

 

sar -b

%rcache < 90% and %wcache < 65%

 

sar -d

%busy > 85% : high utilization, load problem

r+w/s > 65% : overload

 

Example of sar output

 

#> sar -a 5 3
16:59:36 iget/s namei/s dirbk/s
16:59:41      0       0       0
16:59:46      8      26      15
16:59:51    271     297     288

Average      93     108     101
#> sar -b 5 3
16:59:36 bread/s lread/s %rcache bwrit/s lwrit/s %wcache pread/s pwrit/s
16:59:41      19      57      67      22      26      17       0       0
16:59:46      23      73      69      18      23      20       0       0
16:59:51      25      51      51      15      27      46       0       0

Average       22      60      63      18      25      28       0       0
#> sar -d 5 3
13:21:07 device %busy avque r+w/s blks/s avwait avserv
13:21:12 sd1       52   0.8    30    216    4.8   21.1
         sd3        6   0.1     1     14    0.0   45.4
average
         sd1       32   0.5    17    187    3.5   23.9
         sd2       45   0.4    24    208    0.0   18.9
         sd3        4   0.0     1      9    0.0   51.1

 

DISK Solutions


 

1st. Check the file system overload (above 90 or 95% capacity)

2nd. If you have more than one disks,

3rd. Consider adding Memory.

4st. Consider buying faster disks.

5st. Make sure disks are not overloading SCSI controller.

6st. Consider adding disks.

7st. Considering using an in-memory file system for /tmp directory.

 

[ Back ]