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RE: RAC and ASM disk layout

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Date: Mon, 12 Jun 2006 15:16:29 -0400
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The NVRAM is active in iSCSI environments for exactly the reasons you described - an iSCSI target is really just a filesystem file that's exposed, which does create a whole slew of useful functional pieces. For example, if you want to back up all of your Fibre Channel and iSCSI LUNs, you can do so over nfs with a snapshot, etc.

And the iSCSI thing was probably due to using the the full-stack offload cards, which can make a big performance difference. We've just started doing some testing with NFS and the TOE components of those cards, so we'll see if anything interesting bubbles up performance wise.

I actually really like the NetApp model - its very easy to manage, very flexible, and the multi-protocol piece works great for us. We have several hundred systems (mix of real and virtual) that use netapp as their storage in our development lab. With Netapp, we can expose the same data via fibre channel, iSCSI, and NFS, so we can easily distribute storage resources among the different environments. And the WAFL model is one that is tried-and-true, in that its strengths are well-known, its weaknesses are pretty-well documented at this point (though they've been mitigated in OnTap 7). Because of that, you can expect consistent results across different versions of OnTAP, and different netapp hardware platforms. Compare that with HP, HDS, EMC, where different families of products (of course) have vagaries, but there are even fundamental shifts between revisions within the same family.



Matthew Zito
Chief Scientist
GridApp Systems
p: 646-452-4090

-----Original Message-----

[] On Behalf Of Kevin Closson Sent: Monday, June 12, 2006 2:39 PM
To: Oracle-L Freelists
Subject: RE: RAC and ASM disk layout           

        If anybody wants all the bugs out of a product (in this case ASM) before using it, then let's throw all our softs out the window. If you look at any patchset (10gR1 or 10gR2), how many patches you find for ASM, compared to, let's say, CBO? and every body uses CBO.

... all software has bugs. Not all bugs are created equal. Some are bourne out of architecture...some are errant pointers... judge according to your conscience.

        Another point about performance: Netapps say that if you use ASM with iSCSI configuration to go to their disks, it's faster than using NAS (NFS mount the disks). They did the tests, not me. So, if you can live with it, ASM is the way to go.

...bwahahahaha..that is likely because iSCSI is a lighter protocol than NFS. I also suspect that the NVRAM might not be active when a filer is an iSCSI target (somebody in the know please corect me on that point). In general, however, iSCSI from a Netapp filer is a really weird situation. I know very few people on this list care about such subtleties, and thus very few realize that the way NetApp presents an iSCSI target is as follows. The data is stored in blocks in disk, the disks are grouped and managed in volumes, the volumes have a WAFL filesysem with files in it. The Filer presents the files as blocks via the iSCSI protocol...hmmm..




-- Received on Mon Jun 12 2006 - 14:16:29 CDT

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