Re: To ODA or Not?
- From: Jeff Chirco <backseatdba@xxxxxxxxx>
- To: dmarc-noreply@xxxxxxxxxxxxx
- Date: Fri, 27 Mar 2015 16:22:15 -0700
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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