piotrtal wrote:How can you not? Why does it not make sense to consider performance and redundancy?
lets not talk about redudundancy and performance between this two installations, but lets take under consideration its easy deployment and easy maintanance.
damorgan wrote:Agree with the basic sentiment on SANs. Overpriced. With performance issues.
And from my experience everyone is pretty much in your bucket ... they have an existing corporate SAN so they use it. What they often don't realize is that that corporate SAN, almost always EMC, is giving poorer performance than they would get with ZFS or NetApp with a substantial financial savings to the organization. ASM is great ... but shared SANs leave a lot to be desired in most, not all, cases.
piotrtal wrote:Not true. Performance and scalability are directly related to the architecture you use. You cannot fix I/O performance by, for example, getting faster disks - as the problem could be latency in getting that data block from the disk shipped to the database server's memory.
i didn't want to talk about redundancy and performance because
- we can always have external redundancy on physical storage device which should be easier to maintain and performance better.
about NFS vs ASM performance i won't discuss, because i don't possess data about it's difference with performance. nfs is probably worse but main role in this plays IP protocol like one of my precedesor said. but what if company doesn't poses FC infrastructure but only IP (x-Ethernet)?It is not NFS vs ASM. It is NFS (storage protocol) versus FC storage protocol or FCoE or SRP. It is Ethernet vs Fibre Channel or Infiniband. ASM DOES NOT HAVE A PERFORMANCE ROLE. ASM does not write to disk on behalf of the database. ASM is a management layer.
i could only presume that ASM is better but question is: "it is so much performance better that it is worth to install ASM instance on each node to maintain disgroups, and diminish capacity of each node at the same time?" each of ASM instance utilizes ressources (memory/cpu) on node and it could be considered as disadvantage.ASM provides a superior management. Simple example - I have over the past years (and as recent as 2 weeks ago), migrated database storage from one storage system (SAN) to another. Without a single second of database downtime.
even if we consider extensive remote RAC installation (one node is far /distance/ from the other) and we have read-preffered storage parameter set for each ASM instance i wouldn't agree. the same we can obtain on harware level. EMC storages could also replicate between sites, and i don't believe that this hardware replication is worse than software ASM replication.Sorry - I simply do not believe in using RAC where RAC nodes are long distances from one another, or from the clustered storage. That is IMO a nonsensical approach to RAC.
if they don't have FC infrastrucre ther is not possible to use it's advantages.ASM does not need FC infrastructure. ASM manages raw devices for database storage. ASM does not care whether that raw device is a SAN LUN via FC. A local raw disk. A raw device via a SRP LUN. A raw device via SCST target. Etc.