Re: Exadata backups
- From: Andy Colvin <acolvin@xxxxxxxxxxx>
- To: mboligan@xxxxxxxxx
- Date: Tue, 29 Oct 2013 11:31:45 -0700
Mike,
I don't believe that it's true that the storage servers would communicate
directly with the ZFS storage appliance. While everything is connected via an
Infiniband link, the RMAN processes are running on the compute nodes, and (most
importantly) the NFS filesystems are only mounted on the compute nodes.
The main benefits of backing up to a ZFS storage appliance vs any other kind of
NAS are that it's connected over Infiniband, and that there probably isn't
anything else competing for I/O on the backup appliance. We have had clients
run bake-offs comparing EMC, ZFS, and a few others, and almost every time the
ZFS comes out ahead. It's just not a fair fight when you have a 40gbps
connection vs 10GbE.
The "Exadata" specific backup enhancement is simply a localization of the block
change tracking file to each storage server. This way, the storage servers are
able to track the blocks that need to be backed up since the last full or
incremental, freeing up database resources, and allowing the process to be
performed in parallel. This is very different from the actual storage servers
sending the data directly to the ZFS storage appliance.
Thanks,
Andy
Andy Colvin
Principal Consultant
Enkitec
andy.colvin@xxxxxxxxxxx
http://blog.oracle-ninja.com
On Oct 28, 2013, at 3:57 PM, mike boligan <mboligan@xxxxxxxxx> wrote:
> Thanks Alan. So you are saying that the ZFS appliance will read the files
> directly from the cell server and not use any CPU cycles on the compute node?
> I am interested to know more about how that works, there are a couple of
> things that I expect to be true, that must not be for this to work.
> - Things like the RMAN job is kicked off from the compute node, assuming this
> is true somehow the cell server and appliance need to be able to speak
> directly, how is this done? I thought this might be where NDMP comes in.
> - I am pretty sure Oracle said do not install software on the cell nodes, so
> if the cell server and the appliance need to speak I would expect something
> tho be installed for this to work.
> Anything you have to explain the architecture for this is appreciated, I am
> willing to RTFM, I just can't find TFM to R.
>
> Thanks,
> Mike
>
>
>
>
>
> On Monday, October 28, 2013 5:41 PM, Guillermo Alan Bort
> <cicciuxdba@xxxxxxxxx> wrote:
>
> If you have a ZFS appliance, then the RMAN backup can actually be offloaded
> to the storage cells. That alone make exadata + zfs a LOT better than exadata
> + DD.
>
> I've worked a couple of times with DD, but only over ethernet, and I was not
> impressed by the performance and there were a lot of limitations regarding
> number of channels and such. We also had some issues with NFS, but I think
> that was lack of knowledge on our part and not a limitation of the product
> itself. Still, it took a while to get it right with DD.
>
> I was deeply impressed by the speed of both RMAN backups and datapump
> operations to zfs, I reckon this can be accounted for by the InfiniBand
> network, and if you connect datadomain over infiniband you may get similar
> results, with the exception of offloading backup operations to the storage
> cells.
>
> Just to clarify, I've never tried a DD connected to Exadata.
>
> From the DBA point of view, it makes little difference, Exadata is so fast
> and has so many nice QoS features (IORM for one) that you can take backups
> even during daytime and still have little to no effect on the application
> workload (especially OLTP). The only performance difference may be seen
> because with ZFS you can offload backup and restore opration to the cell and
> with datadomain you can't, which means the database server will have to
> process the entire database.
>
> The other issue to consider is whether you want to back up only databases
> residing in the Exadata or if you want to use the backup appliance for other
> things. In the latter scneario I would go with DD.
>
>
>
>
>
> Alan.-
>
>
> On Mon, Oct 28, 2013 at 3:40 PM, hansie <hansrajsao@xxxxxxxxx> wrote:
>
> Mike
>>
>> RMAN is only option for Exadata databases backups irrespective of Oracle
>> ZFS or EMC DD. So backup happens from compute node only. unless you are
>> using DataGuard and taking backup from there. EMC DD is better option for
>> sure.
>>
>>
>> Thanks
>>
>> Hansraj
>>
>>
>>
>> On Mon, Oct 28, 2013 at 1:42 PM, mike boligan <mboligan@xxxxxxxxx> wrote:
>>
>>> We are implementing Exadata and are in the process of evaluating backup
>>> appliances. We are looking at the Oracle ZFS solution and the EMC
>>> Datadomain solution. Anyone go through a similar evaluation recently?
>>> Our storage folks seem to be leaning towards EMC because it has more
>>> administrative features (for things like replicating to a DR site).
>>>
>>> I remember hearing our ACS person mention that the ZFS appliance will
>>> backup Exadata databases going only through the storage cell and not the
>>> compute node. I tried to find something to verify this but am unable to.
>>> If true, this would make this decision pretty easy, if you can confirm or
>>> deny this as well I would appreciate that.
>>>
>>> TIA,
>>> Mike
>>> --
>>> //www.freelists.org/webpage/oracle-l
>>>
>>>
>>>
>>
>>
>> --
>> Thanks,
>> Hansraj
>>
>>
>> --
>> //www.freelists.org/webpage/oracle-l
>>
>>
>>
> --
> //www.freelists.org/webpage/oracle-l
>
>
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