is there any way to increase disk performance ?

[Kris Kennaway]

Tim Judd wrote:
> Yavuz wrote:
>> I have freebsd7 (amd64 bit)  and sata2 disk 7200 rpm.
>>
>> it's running mail server which has services like pop3,imap,smtp and 
>> webmail on this machine.
>>
>> When I type systat 1 -vmstat on command line, even I rarely see that 
>> disk usage hits 100%.
>> I have no problem as ram and cpu.  they is enough.
>>
>> is there any way to increase disk performance without causing any 
>> problem ?
>>
> 
> So in one second, the disk hits 100% utilization, weather it's reading 
> or writing data to disk.  You said above that "I rarely see" -- so even 
> though, as a server, you're running slow spindles, you are doing pretty 
> good.
> 
> I've no real experience with a site that's (for example) been 
> slashdotted, to test what is tolerable, and what's not.  But as I 
> currently guess, an OVERALL average between 25% to 33% is about as much 
> as I would ever tax a server for CONSISTENT averages.
> 
> So if you're seeing it rarely, such as when somebody hits webmail and 
> takes 1 second of constant disk read to serve the content, I'd be happy 
> there...
> 
> I don't think you have a problem, when you put your concern into the 
> broader scope of 1 minute, 1 hour, 1 day or 1 week.  It'll be very 
> difficult to never see 100% in 1 second no matter how powerful the 
> machine is.

Make sure you understand that gstat's "%busy" column does not tell you 
how close to capacity your disk is, it tells you what % of time it is 
handling I/O.  Since modern drives can have many commands queued at any 
given time, those are not the same thing.

To understand whether your disk is overloaded, look at the ms/r and ms/w 
times.

Kris