Re: Oracle Myths

Nuno Souto <nsouto_at_optushome.com.au.nospam> wrote in message news:<3d016125$0$28006$afc38c87_at_news.optusnet.com.au>...
> In article <f369a0eb.0206070954.9b8c87c_at_posting.google.com>, you said
> (and I quote):
>
> Most file systems (ufs, NTFS, etc) will try to allocate space in what
> they think is an "optimal disk use" pattern. For example, in NTFS it's
> almost impossible to obtain a single allocation of disk space larger than
> the MFT size. NTFS will split it into two and place each half on each
> side of the MFT - which sits smack bang in the middle of the partition.
> Like it or not, you end up travelling over the MFT on a full table scan.
> Do two big chunk allocations in that partition and I can guarantee you
> even more fragmentation than just two halves around the MFT.
>

<snip>

Very entertaining. Further suggests that anything LMV, file systems, or things of that nature should be avoided if you want to achieve truly sequential I/O.

> Narh, that's just warehouses. Most dbs out there are much smaller than
> that. Around 1Tb, some much less. Of course warehouses go up to tens of
> Tb and even more. But I've worked in some monster OLTP dbs. Largest one
> is just < 2 Tb and gets about 30Gb of new partitions added per day. Gets

I'd be shocked. That's growth of more than 10 TB a year. If that indeed is what they do I'd be very interested to know how they manage to complete all the merge/purge/transformation and then get the data loaded/updated in a 8-10 hour window.

> purged weekly and monthly into a warehouse, or it would simply not last
> long. That's when all hell can break lose: we had to make sure re-use of
> disk space in file system controlled partitions was still efficient.
Received on Sun Jun 09 2002 - 18:30:35 CDT