Re: Raw Partitions and Oracle

In article <35021D7A.3FB7_at_p3.net>, Jerry Gitomer wrote:

Indeed, AIX volume manager is excellent. The buffering it uses works well, and the filesystems also use Async I/O. (wish I still used AIX!) Using RAW also stops you from using some Oracle features such as AUTOEXTEND on datafiles.

However, on the flip side, you do get more space - filesystems cost 10% of the disk space you allocate, and over 500Gb, this is significant. On DEC Unix 4, you can also use the volume manager to manage your raw partitions more effectively.
Apparently ,you can gain up to 20% more throughput using RAW devices, although I would not guarantee that!

If you understand RAW partitions, and (through benchmarking) you get a noticable performance increase and you are prepared to live with the increased administration and you want (slightly) better scalability and more disk space, use RAW partitions.

Check with the Administration Guide for you platform for more details.

regs

Neil Chandler.

However,
>Hi Declan,
>
>Check the Oracle tuning manual for your operating system instead of the
>general UNIX performance tuning manual. The reason is that for some
>versions of UNIX Oracle is no longer claiming that raw partitions are
>faster. I think this applies to versions of UNIX that have volume
>managers (HP-UX and AIX in particular) which behave differently than
>traditional UNIX.
>
>Regards
>
>Jerry
>
>
>Declan O'Reilly wrote:
>>
>> In the oracle manuals they say that raw partitions are quicker than
>> using files system for tablespaces etc. because it bypass's the overhead
>> of the file system. But I thought that because unix file systems (we
>> are using HP 9000 - 570 using 10.20) buffer data before it writes it to
>> disk, that using a file system would be quicker since the database
>> server would not have to wait for disk access.
>> I thought that the reason for using raw partitions was more for data
>> integrity i.e. the database server would not loose data if the machine
>> crashes and the data is still in the buffer and not yet written to disk.
>> I am missing something
>>
>> Declan O'Reilly
>
>--
>Jerry Gitomer Since I know how to spell DBA I became one.
>jgitomer_at_p3.net
Received on Tue Mar 10 1998 - 00:00:00 CST