Re: MD performance options: More CPU’s or more Hz’s?

[Bill Davidsen <davidsen@tmr.com>]

John Hughes wrote:
> Bill Davidsen wrote:
>> mark delfman wrote:
>>> Hi... I am wondering if anyone can offer some advice on MD performance
>>> related to CPU (speed and or cores).  
>>
>> You didn't ask: if you use ext[34] filesystems, there is a gain to be 
>> had from tuning the stripe and stride parameters, at least for large 
>> sequential io. My measurements were on 2.6.26, so are out of date, 
>> but less head motion is always better. 
> An external journal can be a huge win for ext3 if you are doing lots 
> of file creates/deletes.  (Striped raid, i.e. raid0/raid5/raid6/raid10 
> doesn't help the journal much as it is used sequentially.  In my tests 
> putting the journal on a raid1 and the rest of the fs on a raid10 
> makes things go much faster.  If you have enough disks of course :-))

You might try mounting with data=journal and see what performance you 
get with small reads and writes. Might surprise you. I hadn't thought of 
using raid1 (or raid0 if speed is more important than survival), but I 
have been playing with using SSD just for the journal. As you say, when 
you do lots of creates or deletes it makes a big difference.

-- 
Bill Davidsen <davidsen@tmr.com>
  "We can't solve today's problems by using the same thinking we
   used in creating them." - Einstein