Re: To ODA or Not?
- From: Jeff Chirco <backseatdba@xxxxxxxxx>
- To: dmarc-noreply@xxxxxxxxxxxxx
- Date: Fri, 27 Mar 2015 16:22:50 -0700
We are not using RAC here.
On Fri, Mar 27, 2015 at 4:22 PM, Jeff Chirco <backseatdba@xxxxxxxxx> wrote:
> HI Mladen,
> Thank you for this information. This helps. As far as the redo logs, if
> you put them on the flash storage drive does that help with concerns to the
> snapshots?
> I am still unsure how the snapshot technology works on the ODA. Is it
> similar to NetApp and using SnapManager for Oracle which basically puts all
> the tablespaces in backup mode and then "snaps" the volume and then puts
> the tablespaces out of backup mode?
>
> On Fri, Mar 27, 2015 at 3:18 PM, Mladen Gogala <
> dmarc-noreply@xxxxxxxxxxxxx> wrote:
>
>> On 03/27/2015 05:07 PM, Seth Miller wrote:
>>
>> Jeff,
>>
>> You are in luck. The latest release of the ODA uses ACFS for the
>> database storage which has snapshot/clone technology similar to NetApp.
>> ACFS and all of its snapshotting capabilities are included.
>>
>> Well, that is not exactly true. ACFS uses COW (Copy-On-Write) snapshots
>> which will triple your IO rates on writes. When you write to a file system
>> with the snapshot, the machine must:
>>
>> 1. Read the old data (first I/O operation)
>> 2. Write the old data to snapshot pool block (second IO operation)
>> 3. write the new data to the FS (third IO operation).
>>
>> Not all snapshot technologies are created equal. SAN manufacturers like
>> NetApp usually use so called "deferred write", while file systems like
>> BRTFS, ZFS and ACFS use COW. I would be vewy, vewy cawefull with COW
>> snapshots, as they can significantly slow your system down, especially if
>> redo logs are on the file system with a snapshot.
>>
>> --
>> Mladen Gogala
>> Oracle DBAhttp://mgogala.freehostia.com
>>
>>
>
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