I have a HP DL360 server with 4x 146GB SAS disks and a Smart Array P400i RAID controller with 256MB cache. The disks are in RAID 5 (3 disks + 1 hot spare).

The server is running VMware ESX 3i.

The disk write performance is really bad. Here are some numbers:

> 
> ns1:~# hdparm -tT /dev/sda
> 
> 
> /dev/sda:  
> 
>  Timing cached reads: 3364 MB in 2.00 seconds = 1685.69 MB/sec  
> 
>  Timing buffered disk reads: 18 MB in 3.79 seconds = 4.75 MB/sec
> 
> 
> ns1:~# time sh -c "dd if=/dev/zero of=ddfile bs=8k count=125000 && sync"  
> 
>  125000+0 records in  
> 
>  125000+0 records out  
> 
>  1024000000 bytes (1.0 GB) copied, 282.307 s, 3.6 MB/s  
> 
> 
> 
> real 4m52.003s  
> 
>  user 0m2.160s  
> 
>  sys 3m10.796s
> 
> 
> 

Compared to another server those number are terrible: Dell R200, 2x 500GB SATA disks, PERC raid controller (disks are mirrored).

> 
> web4:~# hdparm -tT /dev/sda
> 
> 
> /dev/sda:  
> 
>  Timing cached reads: 6584 MB in 2.00 seconds = 3297.79 MB/sec  
> 
>  Timing buffered disk reads: 316 MB in 3.02 seconds = 104.79 MB/sec  
> 
> 
> 
> web4:~# time sh -c "dd if=/dev/zero of=ddfile bs=8k count=125000 && sync"  
> 
>  125000+0 records in  
> 
>  125000+0 records out  
> 
>  1024000000 bytes (1.0 GB) copied, 35.2919 s, 29.0 MB/s  
> 
> 
> 
> real 0m36.570s  
> 
>  user 0m0.476s  
> 
>  sys 0m32.298s
> 
> 
> 

The server isn't very loaded and the VMware Infrastructure Client performance monitor is showing 550KBps average read and 1208KBps average write for the last 30 minutes (highest write rate: 6.6MBps).

This has been a problem from the start. Any ideas?