Re: type of striping

From: Fabrizio <fabrizio.magni_at_mycontinent.com>
Date: Wed, 08 Dec 2004 09:30:11 GMT
Message-ID: <DQztd.478201$35.20545375@news4.tin.it>

Howard J. Rogers wrote:
> Fabrizio wrote:
>

>> Howard J. Rogers wrote:
>>
>>>
>>> Autoallocate is probably my preferred way of creating LMTs.
>>>
>>
>>  From your old posts I always thought you preferred the "uniform size" 
>> for LMTs.
>>
>> May I ask you the advantages of autoallocate?
>>

>
> Ah... I just answered you via email, because that showed up before this
> post. Could I ask you not to email me things you are also going to post
> to the newsgroup? That way, I don't get confused! (Happy to have email
> for other stuff, of course). Anyway...
>

Opss, this is because I use "reply all". I'll strip your personal email from the list. My apologies.

However I haven't received any email from you. If you simply replied it should have bounced back.

> It's true I was always a little suspicious of autoallocate, because it
> was very difficult to pin down precisely what extent sizes you were
> going to get. I hesitate to recommend anything I don't really understand.
>
> But that changed a long time ago. I now believe that DBAs really
> shouldn't have to worry about extent sizing at all, and autoallocate
> takes that chore away completely. PCTINCREASE used to do something
> similar, of course, with the same sort of 'automation' claims, but the
> consequence was horrendous fragmentation issues... autoallocates don't
> fragment (or exceedingly rarely, anyway).
>
> > May I ask you the advantages of autoallocate?
> >
>
> Total automation for one.
>
> For another, ASSM is in widespread use, and that makes the number of
> extents an issue again. Autoallocate minimises the number of extents.
> Poorly chosen uniform sizes will cause grief with ASSM.
>

But what about uniform sized extents without ASSM (in a non-RAC system)?

> Besides which... look at what 10g is doing with ASM, and you'll see that
> the days of ever worrying about extents are (or should be) long, long ago.
>

I believed that with ASSM a DBA should go back to count extents... and I can see fragmentation introduced by autoallocate.

These and fear about ASSM performance and bugs made me wonder if to recreate some of the tablespaces to "uniform size". Now I'm more confused.

(I'll reserve questions on ASM for another thread).

> But I'm not religious about it. If you want to steer clear of
> autoallocates (perhaps because of the no striping issue discussed
> earlier, and your particular hardware) that's fine, too.
>

I have not position here. I'm trying to evaluate pros and cons.

Regards

-- 
Fabrizio Magni

fabrizio.magni_at_mycontinent.com

replace mycontinent with europe

Received on Wed Dec 08 2004 - 03:30:11 CST