RE: Oracle and NAS storage systems

How timely! It just so happens that we've got some NetApp sales droids coming in on Wednesday and we're gonna get an eval box to play with... but don't tell anybody. ;-)

NAS "toasters" (appliances) are implemented with RAID 4 enhancements and WAFL technology from NetApp.

NetApp wants to claim that NAS is just as fast as RAID or SAN but I'm skeptical thinking the limitations of NFS are a problem. Ever hear about a thing called network latency? Even if you make dedicated network connections there could be problems. NetApp filers now support both NFS version 2 and NFS version 3 and I think this is key. NFS Version 2 writes are synchronous requiring the server to flush data to disk before replying to the NFS client (the Oracle RDBMS) so the client has to wait thus creating a significant performance limitation. NFS version 3 tries to overcome this speed limitation by implementing a two phased commit write operation. Version 3 NFS clients can submit async write requests which the server can immediately acknowledge. But if the NFS v3 server fails some data may not actually be written to disk and can be lost so it's up to the NFS v3 client to recover. Upon failure and error notification to the NFS client, the NFS client must resync/resubmit write requests from cache. So the onus is on the NFS v3 client to coordinate messages from the NFS server and confirm that the data has been written to disk. How (and how efficiently!) the Oracle/NetApp NFS client does this is still a mystery to me.

(Anyone go to the NetApp presentation at OOW? What a meltdown!! I never saw a speaker so challenged and humiliated before... it was painful to watch. Our friend Jeremiah has a lot of healthy negativity on this. :-)

Here's an old post on the subject:
http://groups.google.com/groups?selm=Pine.OSF.3.95.981013212349.4502A-100000 %40gonzo.wolfenet.com

Dick...
> they [EMC] do not recommend doing so [implementing NFS datafiles] for
> several of the reasons that I've held out.
Spill dude!! I'm looking for some more ammo for my Wednesday NetApp sales droid confrontation. :-) (Back channel OK.)

AtDhVaAnNkCsE!

Steve Orr
Bozeman, Montana

-----Original Message-----
Sent: Monday, July 15, 2002 10:23 AM
To: Multiple recipients of list ORACLE-L

I think that NA uses RAID4. This is the same as RAID5, but the parity info is not stripped across the disks. This allows them to add disks from the spare spool very quickly, as parity info does not need to be recalculated. Spare disks are simply 'zeroed-out' prior to use.

> -----Original Message-----
> From: DENNIS WILLIAMS [SMTP:DWILLIAMS_at_LIFETOUCH.COM]
> Sent: Monday, July 15, 2002 11:58 AM
> To: Multiple recipients of list ORACLE-L
> Subject: RE: Oracle and NAS storage systems
>
> Dick -
> We use NetAppliance to store Oracle datafiles on our test system. I am
> pretty sure the NetAppliance is configured as RAID5. I would rate it as
> quite satisfactory for that purpose. We have many test systems and they
> are
> only used sporadically.
> I have had no reliability issues with the NetAppliance, so I can't
> figure
> what EMC means by it being "risky".
> I did find that if performance is pushed to a high level, the
> NetAppliance seems to have problems. I can't say for sure whether the
> problem is with the NetAppliance or with a network bottleneck. For
> example,
> I was going to rebuild 5 or 6 large indexes. Both the table and the index
> were on the NetAppliance system. I started a script to simultaneously
> build
> these indexes and went home for the night. Based on my experience with our
> normal RAID5 drives, I came in the next morning fully expecting all those
> indexes to be built. None of the indexes got rebuilt. My guess is that
> there
> was too much contention. I built the indexes one at a time, moving the
> base
> table to a normal RAID5, and performance was quite satisfactory. Have had
> no
> further problems or test user complaints.
> I wouldn't commit to using NAS on a system that will push the disk
> drive
> subsystem really hard. Maybe for a less-critical system that needs access
> to
> large amounts of cheap disk. Test first. I have also heard of a lot of SAN
> systems being mis-configured and producing poor or erratic database
> performance.
>
> Dennis Williams
> DBA
> Lifetouch, Inc.
> dwilliams_at_lifetouch.com
>
> -----Original Message-----
> Sent: Monday, July 15, 2002 9:43 AM
> To: Multiple recipients of list ORACLE-L
>
>
> Folks,
>
> I've been asked to validate/invalidate a contention made by two
> storage
> vendors.
>
> NetAppliance has stated that you can use a netapp filer with Oracle
> for
> datafiles, although their configuration looks more like a DAS(direct
> attached
> storage) configuration using 10baseT cables vs. SCSI cables. Of course
> their
> real claim to fame here is Oracle's endorsement.
>
> EMC on the other hand has stated that using a NAS, in the traditional
> mode,
> for Oracle datafiles is at best risky. And although their product can
> support
> it, they do not recommend doing so for several of the reasons that I've
> held
> out
> are pertinent.
>
> Therefore, is there anyone out their using a NAS to store datafiles?
> If
> so,
> what does the configuration (server to NAS) look like?
>
> Dick Goulet
> --
> Please see the official ORACLE-L FAQ: http://www.orafaq.com
> --
> Author:
> INET: dgoulet_at_vicr.com

-- 
Please see the official ORACLE-L FAQ: http://www.orafaq.com
-- 
Author: Orr, Steve
  INET: sorr_at_rightnow.com

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