[Vserver] Tuning HD performance

From: Arnór Kristjánsson <addi_at_bhs.is>
Date: Mon 28 Aug 2006 - 15:40:38 BST
Message-Id: <3E8FBB7F-67E5-4A65-B366-6FAFE03FD5CD@bhs.is>

Hi,

I'm running a vserver running various LAMP servers. A while ago I
installed munin to check how the server was behaving at various
times. It turns out that the server has a LOT of iowait (up to 115)
when under load.

What I did was that I ran tiobench on the local HD and this is what I
got:

--
Sequential Reads
                               File  Blk   Num                    
Avg      Maximum      Lat%     Lat%    CPU
Identifier                    Size  Size  Thr   Rate  (CPU%)   
Latency    Latency      >2s      >10s    Eff
---------------------------- ------ ----- ---  ------ ------  
--------- -----------  -------- -------- -----
2.6.14.3-vs2.0.1              100   4096    1  446.29 99.97%      
0.006        0.04   0.00000  0.00000   446
2.6.14.3-vs2.0.1              100   4096    2  728.70 396.4%      
0.007        0.05   0.00000  0.00000   184
2.6.14.3-vs2.0.1              100   4096    4  855.43 1587.%      
0.011        0.20   0.00000  0.00000    54
2.6.14.3-vs2.0.1              100   4096    8  839.09 2328.%      
0.013       56.08   0.00000  0.00000    36
Random Reads
                               File  Blk   Num                    
Avg      Maximum      Lat%     Lat%    CPU
Identifier                    Size  Size  Thr   Rate  (CPU%)   
Latency    Latency      >2s      >10s    Eff
---------------------------- ------ ----- ---  ------ ------  
--------- -----------  -------- -------- -----
2.6.14.3-vs2.0.1              100   4096    1  418.79 96.48%      
0.006        0.02   0.00000  0.00000   434
2.6.14.3-vs2.0.1              100   4096    2  754.47 386.3%      
0.006        0.04   0.00000  0.00000   195
2.6.14.3-vs2.0.1              100   4096    4  839.15 1374.%      
0.010        0.05   0.00000  0.00000    61
2.6.14.3-vs2.0.1              100   4096    8  739.47 870.8%      
0.009        0.04   0.00000  0.00000    85
Sequential Writes
                               File  Blk   Num                    
Avg      Maximum      Lat%     Lat%    CPU
Identifier                    Size  Size  Thr   Rate  (CPU%)   
Latency    Latency      >2s      >10s    Eff
---------------------------- ------ ----- ---  ------ ------  
--------- -----------  -------- -------- -----
2.6.14.3-vs2.0.1              100   4096    1    6.89 4.602%      
0.021        9.83   0.00000  0.00000   150
2.6.14.3-vs2.0.1              100   4096    2    9.12 15.32%      
0.031       80.06   0.00000  0.00000    60
2.6.14.3-vs2.0.1              100   4096    4    9.65 52.36%      
0.040        0.54   0.00000  0.00000    18
2.6.14.3-vs2.0.1              100   4096    8    9.92 102.5%      
0.066      100.08   0.00000  0.00000    10
Random Writes
                               File  Blk   Num                    
Avg      Maximum      Lat%     Lat%    CPU
Identifier                    Size  Size  Thr   Rate  (CPU%)   
Latency    Latency      >2s      >10s    Eff
---------------------------- ------ ----- ---  ------ ------  
--------- -----------  -------- -------- -----
2.6.14.3-vs2.0.1              100   4096    1    0.34 0.148%      
0.010        0.03   0.00000  0.00000   230
2.6.14.3-vs2.0.1              100   4096    2    0.34 0.352%      
0.011        0.06   0.00000  0.00000    98
2.6.14.3-vs2.0.1              100   4096    4    0.37 1.033%      
0.017        0.07   0.00000  0.00000    36
2.6.14.3-vs2.0.1              100   4096    8    0.38 1.596%      
0.016        0.14   0.00000  0.00000    24
--
I'm wondering; shouldn't the CPU % be lower on reads? Is there a way  
to increase this performance?
A.
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Received on Mon Aug 28 18:32:25 2006
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