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Consider the following five machines (named c, h, j, s and u) and their respective vmstat 1 outputs.

Given the information from the vmstat output:

  • Which machines would you consider being in a good shape? Why? What's your reasoning?
  • Which machines would you consider being in a bad shape? Why? What's your reasoning? How would you go about fixing it? Upgrade memory, CPU, IO-subsystems or something else?

I'm trying to learn how to get an intuitive feel for interpreting vmstat output.

Machine c:

 # vmstat 1
 procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
  1  0      4   9456  10692 304020    0    0   193    92  310  131  7  1 80 11  2
  2  0      4  10212  10676 303020    0    0   412    40 1265  514 11  0 80  8  2
  1  1      4   9664  10684 303328    0    0   320    60 1311  545  7  0 84  7  2

Machine h:

 # vmstat 1
 procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
  0  2 892948  10084  11352 140248   14    9    67   113  123  184  1  0 81 13  4
  1  1 892948   9828  11360 140420   80    0   232    56 1436  839  1  0 74 24  2
  0  1 892948   9424  11368 140596   88    0   192   780 1405  564  1  0 74 23  2

Machine j:

 # vmstat 1
 procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
  0  2    300 152276   7432 616948    0    3   922   795   38   29  8  1 65 25  0
  0  0    300 152096   7436 617136    0    0   184     0  243  421  2  1 77 20  0
  0  0    300 152096   7436 617136    0    0     0    28  160  285  0  0 100  0  0

Machine s:

 # vmstat 1
 procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
  0  0  57748 213168  17672 1282888    0    0    23     6    0    0 11  1 79  9  0
  0  0  57748 213224  17676 1282900    0    0    24     0   33  503  1  0 98  1  0
  0  0  57748 213224  17676 1282900    0    0     0     0    7  254  0  0 100  0  0

Machine u:

 # vmstat 1
 procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
  r  b   swpd   free   buff  cache   si   so    bi    bo   in   cs us sy id wa st
  0  3 452708   8860   2724 266032   34   16   248   244    5   15  5  3 72 19  1
  0  2 452708  62240   2776 211880  292    0  1952     0  625  749  9  2 70 18  1
  1  1 452708  63752   2832 212320  228    0   816     0  745  821  4  0 67 28  1
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2 Answers 2

up vote 2 down vote accepted

Too short periods. It would be better to have vmstat 60. Well, nevertheless:

  • c - is OK.
  • h - has something in si/so. Taking into account the large swpd, if you find the performance less than acceptable, add 521-1024 MB more RAM (892948 kB ideally).
  • j - is OK.
  • s - is OK. A little bit swpd, but no si/so.
  • u - has quite a lot si/so. Taking into account the large swpd, you probably find the performance less than acceptable, and you should add 512 MB of RAM (452708 kB ideally).

None of your system needs more CPU.

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It's hard to say with these extremely brief snapshots, but if the iowait continues to be non-zero on c, faster drives might be in order. Aside from that, I agree with kubanskamac's assessment. –  Insyte Aug 16 '09 at 2:38
    
I forgot that vmstat lists in kB in Linux, not in 4 kB pages; I've adjusted my answer. –  kubanczyk Aug 17 '09 at 9:04

Take a look at the vmstat man page I'd say u, s, h would benifit from more RAM assigned, high swap usage.

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