Re: To ODA or Not?
- From: "Mladen Gogala" <dmarc-noreply@xxxxxxxxxxxxx> (Redacted sender "mgogala@xxxxxxxxx" for DMARC)
- To: oracle-l@xxxxxxxxxxxxx
- Date: Fri, 27 Mar 2015 18:18:06 -0400
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 DBA
http://mgogala.freehostia.com
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