Oracle Database Appliance — Storage expansion with NFS (dNFS, HCC)
Mar 26, 2012 / By Alex Gorbachev
The biggest objection to Oracle Database Appliance (ODA) we hear from customers is about 4TB usable space limit (tripple mirrored 12TB of raw storage). I think most of the times this is more a perceived barrier rather than objective — more along the lines of being afraid to hit the limit if the system grows a lot. Nevertheless, Oracle has been always listening customers’ concerns when it comes to purchasing barriers. Of course, this time is no exception.
4TB is limit no more
NFS was always a good option to store your ODA database backups. Now there is a simple way to go beyond 4 TB storage limitation — ODA is now fully supporting read-write NFS-mounted external storage for database files. The recommendation is to use Oracle ZFS Storage Appliance (ZFSSA) since this is what Oracle has been testing extensively with. However, there is no reason why it can’t work with other NAS storage.
Direct NFS is your friend
Whether you are using ZFSSA or another NAS storage device, Direct-NFS (dNFS) can be used (I haven’t tested it yet myself) instead of standard Linux “kernelized” NFS — this allows for a more efficient NFS IO with better performance and scalability and reduced CPU overhead doing NFS IO.
Usage of ZFS Storage Appliance will make Hybrid Columnar Compression (HCC) available for ODA customers. HCC is the technology that originally appeared with Exadata only but has recently become available to Oracle Database customers using ZFSSA and Pillar as the database storage. HCC is actually free with Oracle Database Enterprise Edition — no additional database options and no additional ZFSSA options are required. However, HCC does require Oracle Database version 126.96.36.199 while the latest ODA patchset runs 188.8.131.52 version but wait… 184.108.40.206 will be on ODA in April it seems so stay tuned.
Do you appliance?
One thing to remember with external NFS storage for ODA is the new dependency and, as a result, you now need to take care of storage availability yourself. This somewhat breaks the all-in-one appliance idea — you need to manage your storage which is more work (and coordination between storage and DBA team) than just racking in a singe 4U ODA device. One way to limit dependency of ODA on external storage is to use NFS mounted storage for read-only data in read-only tablespaces and set
READ_ONLY_OPEN_DELAYED parameter to
Just like if your were to use NAS for backups, it’s advised to segregate NFS IO traffic on separate bonded pair of NICs and that’s where ODA has plenty of capacity with six 1Gbit and two 10Gbit NICs.
And good timing for Pythian — a new shiny ZFS 7320 Storage Appliance should show up at our office any day now.
If you haven’t yet considered a new Oracle Database Appliance for your next project, drop us a line at email@example.com.
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