[CentOS] how to optimize CentOS XEN dom0?

Wed Feb 23 08:42:53 UTC 2011
Rudi Ahlers <Rudi at SoftDux.com>

On Wed, Feb 23, 2011 at 9:06 AM, yonatan pingle
<yonatan.pingle at gmail.com> wrote:
> you should have a look at your I/O disk status.
>
> try with iostat -dx 5 to see the disk utilization info over time.
> when it comes to slowdown on a virtual environment on a Desktop grade
> machine,  i suspect disk I/O latency and bottleneck as a cause.

Thanx, I don't know how to interpret the results (yet), but here's the
current output:


Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz
avgqu-sz   await  svctm  %util
sda               0.00    27.20  0.00  6.80     0.00   448.00    65.88
    0.00    0.59   0.35   0.24
sda1              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
sda2              0.00    27.20  0.00  6.80     0.00   448.00    65.88
    0.00    0.59   0.35   0.24
dm-0              0.00     0.00  0.00 27.80     0.00   222.40     8.00
    0.01    0.35   0.09   0.24
dm-1              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-2              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-3              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-4              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-5              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-6              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-7              0.00     0.00  0.00  0.40     0.00     6.40    16.00
    0.00    0.00   0.00   0.00
dm-8              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-9              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-10             0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-11             0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-12             0.00     0.00  0.00  2.80     0.00    97.60    34.86
    0.00    0.00   0.00   0.00
dm-13             0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-14             0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-15             0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-16             0.00     0.00  0.00  3.00     0.00   121.60    40.53
    0.00    0.00   0.00   0.00
dm-17             0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00

Although, most of those values change the whole time, as such:

Device:         rrqm/s   wrqm/s   r/s   w/s   rsec/s   wsec/s avgrq-sz
avgqu-sz   await  svctm  %util
sda               0.00     1.00  0.00  0.80     0.00    17.60    22.00
    0.00    0.00   0.00   0.00
sda1              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
sda2              0.00     1.00  0.00  0.80     0.00    17.60    22.00
    0.00    0.00   0.00   0.00
dm-0              0.00     0.00  0.00  1.40     0.00    11.20     8.00
    0.00    0.00   0.00   0.00
dm-1              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-2              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-3              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-4              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-5              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-6              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-7              0.00     0.00  0.00  0.40     0.00     6.40    16.00
    0.00    0.00   0.00   0.00
dm-8              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-9              0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-10             0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-11             0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-12             0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-13             0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-14             0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-15             0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-16             0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00
dm-17             0.00     0.00  0.00  0.00     0.00     0.00     0.00
    0.00    0.00   0.00   0.00




>
> check that your disk is running at its optimal state.
> look at some indicators , such the the I/O utilization averages,
> server load averages
> hddtemp /dev/sda will check for heating ( under high load it might )
>
> in any case , you still got plenty of ram to spend.
>


The HDD temp is 52 degrees Celsius, and according to the SNMP stats,
it's been on average between 48 & 54 for the past 3 months now. But,
every other server that I just checked is between 16 degree & 38
degrees. This is the hottest machine which means I need to add some
extra cooling to it. it's a 1U chassis that we "inherited"  when we
acquired another company a while ago, and it was (still is to some
degree) to move everyone to a new server so we keep it alive for now.



root at zaxen01:[~]$ smartctl -l scttemp /dev/sda
smartctl version 5.38 [x86_64-redhat-linux-gnu] Copyright (C) 2002-8 Bruce Allen
Home page is http://smartmontools.sourceforge.net/

=== START OF READ SMART DATA SECTION ===
SCT Status Version:                  3
SCT Version (vendor specific):       522 (0x020a)
SCT Support Level:                   1
Device State:                        Active (0)
Current Temperature:                    52 Celsius
Power Cycle Min/Max Temperature:     50/53 Celsius
Lifetime    Min/Max Temperature:     22/60 Celsius
Under/Over Temperature Limit Count:   0/594
SCT Temperature History Version:     2
Temperature Sampling Period:         1 minute
Temperature Logging Interval:        1 minute
Min/Max recommended Temperature:      0/ 0 Celsius
Min/Max Temperature Limit:            0/ 0 Celsius
Temperature History Size (Index):    128 (24)

Index    Estimated Time   Temperature Celsius
  25    2011-02-23 08:33    52  *********************************
 ...    ..(  7 skipped).    ..  *********************************
  33    2011-02-23 08:41    52  *********************************
  34    2011-02-23 08:42    53  **********************************
  35    2011-02-23 08:43    52  *********************************
  36    2011-02-23 08:44    52  *********************************
  37    2011-02-23 08:45    52  *********************************
  38    2011-02-23 08:46    53  **********************************
  39    2011-02-23 08:47    52  *********************************
 ...    ..(  2 skipped).    ..  *********************************
  42    2011-02-23 08:50    52  *********************************
  43    2011-02-23 08:51    53  **********************************
  44    2011-02-23 08:52    52  *********************************
 ...    ..(107 skipped).    ..  *********************************
  24    2011-02-23 10:40    52  *********************************




-- 
Kind Regards
Rudi Ahlers
SoftDux

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