current access to file systems

Dave Howorth dhoworth at mrc-lmb.cam.ac.uk
Thu Jul 22 10:04:31 UTC 2010


Peng Yu wrote:
> On Sat, Jun 19, 2010 at 9:41 PM, Sandy Harris <sandyinchina at gmail.com> wrote:
>> On 6/19/10, Peng Yu <pengyu.ut at gmail.com> wrote:
>>
>>>  I'm seeking for a solution in ubuntu to address the concurrent disk
>>>  access problem that are described below. ...
>>>
>>>  I have one machine (8 CPUs and 40GB RAM) ...
>>> I run a speed test ... (8 process running simultaneously) ...
>>>  NOTE, in the future I may need to expand the system from just one
>>>  machine to multiples machines, which all access the same storage
>>>  space.
>> I would be looking at a hardware RAID controller. They are not cheap,
>> but not out of proportion relative to your CPU & RAM costs. Better
>> reliability which is probably important if many things depend on the
>> storage. Reduced CPU load, caching, ...
> 
> Sorry for the late reply. I just saw your email. Would you please let
> me know why RAID controller might help me in this case? Does RAID
> controller somehow buffer the data and write them a large chunk at
> once? Do you recommend any brand? What specifications of the
> controller I should look at to make sure that it matches my machine?

Peng Yu, you can answer your questions about RAID yourself. If you don't
know what RAID does, you need to educate yourself first. Do some
browsing. For your application you're looking to get benefits from
striping and you probably don't need a special controller. You can use
Linux software RAID (google for mdadm or look at wikipedia etc).

But when you talk about multiple machines accessing the same disk
storage, when one is already saturating the disk, you're going to a
whole different level. You probably need to do a fundamental review of
your application design to see how to avoid that requirement. It sounds
to me like you need a new system architecture. But that's well outside
the scope of this list.

Cheers, Dave






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