Re: ODA 12.1.2 Databases on ACFS
- From: Seth Miller <sethmiller.sm@xxxxxxxxx>
- To: dmarc-noreply@xxxxxxxxxxxxx
- Date: Mon, 26 Jan 2015 08:43:08 -0600
Thanks Mladen. I appreciate your feedback.
ODA is certainly not just a Linux box with Oracle, ASM and ACFS. And yes,
it is RAC.
Seth Miller
On Mon, Jan 26, 2015 at 6:07 AM, Mladen Gogala <dmarc-noreply@xxxxxxxxxxxxx>
wrote:
> On 01/25/2015 11:40 PM, Seth Miller wrote:
>
>> As of release 12.1.2.0 of the ODA software, all database are created on
>> ACFS (CloudFS) by default.
>>
>> Has anyone implemented this strategy outside of the ODA?
>>
>> If you have used this on ODA or otherwise, do you have any feedback on it?
>>
>> Are you utilizing the snapshot ability?
>>
>> Seth Miller
>>
> I have tested ACFS on a normal Oracle 12c RAC system with 2 Dell boxes,
> connected to a NetApp filer. The systems were running RHEL 6.5, 64bit. LUNs
> were "scsified" (no ASMLib) and put into ASM. The kernel had no problems
> building the ACFS drivers and the database performance was quite good, but
> there . ACFS One notable omission is that there is no defragmenter, which
> is not very important for a database, but is important if you want to keep
> other types of files which are frequently created and deleted, like archive
> logs. Snapshots, however, are CoW (copy on write) and that method has known
> drawback of tripling the IO rate for writes because the kernel has to do
> the following:
>
> 1) Read the old data
> 2) Write the old data to the snapshot pool location
> 3) Write the new data.
>
> That is what "copy-on-write" means. You will do that for every FS block
> and for every snapshot. If there are two snapshots of your database, the
> system will do 6 IO operations for every write request. With all due
> respect to Dell, their IO throughput is not unlimited, so the whole thing
> slows down considerably. Fortunately, SAN manufacturers, like NetApp have
> much smarter strategy known as "deferred write snapshot" which was used
> instead.
> Personally, I have installed Oracle 12c on Fedora 20 with Brtfs, precisely
> in order to test snapshots. The results show the same problem as above. My
> desktop box slows down to a crawl when inserting a million rows into the
> database using Perl script to avoid the well known PL/SQL optimization with
> commits within the loop. In addition to that, once you use the files on
> ACFS, there is no balancing keeping the files populated to the same level.
> Since this was only a test configuration, the production DB is still
> running 11.2.0.4, the client eventually decided to use ASM instead of ACFS.
> I have no experience with ODA, but my understanding is that it is a Linux
> box with Oracle, ASM & ACFS, no RAC.
>
>
> --
> Mladen Gogala
> Oracle DBA
> http://mgogala.freehostia.com
>
> --
> //www.freelists.org/webpage/oracle-l
>
>
>
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