Re: type of striping

From: Chuck <skilover_at_softhome.net>
Date: Tue, 07 Dec 2004 16:05:49 -0500
Message-ID: <31mk9dF3b2jveU1@individual.net>

Howard J. Rogers wrote:
> Chuck wrote:
>

>> Frank van Bortel wrote:
>>
>>> yls177 wrote:
>>>
>>>> Hi, i understand that there are different types of striping for raid 0.
>>>>
>>>> 1) OS/Hardware striping
>>>> 2) manual striping
>>>>
>>>> And the general consenus is that OS/Hardware striping is better than 
>>>> manual.
>>>>
>>>> Please advise
>>>
>>>
>>>
>>>
>>> Advise what?
>>> Against the general consensus? Which would probably be hardware
>>> over software, btw.
>>>
>>> How would you stripe manually?!? Get your sleeves rolled up,
>>> put on your high voltage protection gloves, and jump into the
>>> computer case?
>>>
>>
>> By manual striping, I think he meant the old practice of manually 
>> pre-allocating extents to specific datafiles. I don't think anyone 
>> does this anymore. Back in v7 Oracle used to allocate extents in a 
>> different way than it does today. If you had multiple datafiles in a 
>> tablespace, it would fill the first datafile, then the second, etc. 
>> Now it distributes the extents evenly across all datafiles in the 
>> tablespace, effectively doing automatically what DBA's used to have to 
>> do manually. You can probably still find references to manual striping 
>> in the old v7 manuals if they are still online anywhere.
>> -- 
>> Chuck

>
>
>
> Just thought I'd mention that in fact, things were and are, precisely
> the opposite way around. In a multi-file tablespace in 8.0, for example,
> Oracle would allocate the initial extent on file 1, the next on file 2,
> the next on file 3, then back to file 1, 2, and so on. It would, in
> short, "round robin" the extents.
>
> In locally-managed tablespace, it hammers disk 1 to death and only moves
> on to disk 2 when no more space is available on disk 1 *IF* the
> tablespace is AUTOALLOCATE LMT. If you do UNIFORM SIZE LMT, then the
> round robin behaviour is unchanged.

That's all I ever use is uniform size LMT's. IIRC however the behavior in v7 (which only had DMT's) was to fill one datafile before moving to the next.

Thanks for the info on the different behavior with auto allocate LMT's. For me, that's one more reason to avoid them. Received on Tue Dec 07 2004 - 15:05:49 CST