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    Why are some DBA's averse to using ASM?

    user4397602
      We are upgrading to 11GR2 from 10G and are looking at the pros and cons of using ASM vs AIX JFS2. We are currently on HP-UX on Itanium and it's easy to guess why we are considering moving to AIX. We only have single instance databases and have no plans for using RAC. Half the DBA's in our organization are averse to using ASM citing complexity among other reasons. We asked a few other DBA's in other organizations we knew and were told that they too only use ASM for RAC and avoid it for single instance databases. I think ASM should be used for all Oracle databases esp 11G due to the obvious benefits.

      I looked at the polling for ASM on this forum and see that more DBA's are now using ASM for Single Instance Databases. But then I wonder why many don't? Any comments are appreciated.


      "Which Oracle DB configuration do you currently use with ASM?
      Votes: 176
      40%     RAC database only

      13%     Single Instance databases only

      28%     More RAC databases than Single Instance database

      8%     More Single Instances databases than RAC databases

      9%     Not yet using ASM "

      Edited by: user4397602 on Jun 19, 2012 10:10 PM
        • 1. Re: Why are some DBA's averse to using ASM?
          asifkabirdba
          We have used file system in RAC but now in a new environment we are using 11g and ASM.


          In ASM

          1. Database physical files are very easy to manage.

          2. When you add or remove disk groups in ASM , it will automatically rebalanced the datafiles through ASM disk groups. You don't need to move the datafiles in mount point taking downtime.

          3. Its now DBA responsibility to manage the ASM which using raw disk device. In this case DBA need to play system admin role for ASM.

          4. ASM is faster than file system as people said but it will be said by a DBA who migrated his database server to ASM and compare the performance to file system.


          In my view go for ASM but before going to live play with ASM in test environment.


          Regards
          Asif Kabir
          • 2. Re: Why are some DBA's averse to using ASM?
            Billy~Verreynne
            I think ignorance is the main reason. Not understanding what ASM is, and how and where it fits into the s/w stack.

            These days, the only time that I do not use ASM (even with a single db instance) is Oracle XE - as ASM is not included. And yes, we are even using Oracle XE on a couple of production servers as a "data management device" (with lots of flexibility and features) for Java code, without having to worry about licensing and maintenance costs.

            The only other time that ASM is not suited is when the only database storage option is cooked file systems. But running less and less into this - even on small servers. The 2nd or 3rd (or both) drives are left unformatted and assigned as raw devices for ASM to use.

            Been using ASM for well over 5 years now. Not once have I ever had a situation where I thought "+dammit, wished I did not use ASM+". Had plenty of situations though where ASM made a MAJOR difference in storage migration, and dealing with storage layer errors and problems - where it basically saved the day so to speak.

            So not using ASM? The thought "+you poor dumb and ignorant sod..."+ comes to my mind.
            • 3. Re: Why are some DBA's averse to using ASM?
              698658
              >
              Been using ASM for well over 5 years now. Not once have I ever had a situation where I thought "dammit, wished I did not use ASM". Had plenty of situations though where ASM made a MAJOR difference in storage migration, and dealing with storage layer errors and problems - where it basically saved the day so to speak.
              >

              Dont get me wrong I totally agree but there is a case when ASM can make You @#$@% . Its because different file locking and You can overwrite living database with badly configured rman restore .
              Regards
              GregG
              • 4. Re: Why are some DBA's averse to using ASM?
                EdStevens
                user4397602 wrote:
                We are upgrading to 11GR2 from 10G and are looking at the pros and cons of using ASM vs AIX JFS2. We are currently on HP-UX on Itanium and it's easy to guess why we are considering moving to AIX.
                <snip>

                Just an aside comment ... it's easy to guess why you are leaving Itanium, but not so easy o guess why moving to AIX. It has some quirks of its own, and you are still paying for dedicated hardware software. why not move to Oracle Linux on commodity hardware? No, I'm not a sales guy, and have not vested interest. But given that Linux is all but free and you can run it on generic hardware, the cost argument is pretty compelling. As for the technical merits of AIX, I've used it and have no complaints, but it is surprising how often the oracle docs have to include side notes pointing out special considerations for AIX vs. any other *nix.                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       
                • 5. Re: Why are some DBA's averse to using ASM?
                  Billy~Verreynne
                  GregG wrote:

                  Dont get me wrong I totally agree but there is a case when ASM can make You @#$@% . Its because different file locking and You can overwrite living database with badly configured rman restore.
                  But change control and operational management must be seriously fubar'ed for something like that to happen, no? :-)

                  I would not call this an ASM issue specifically. Someone just as well can pull a fibre cable on the SAN side, or some clever sysadmin may try a mkfs on a scsi disk already allocated to an ASM diskgroup... IOW, this is @#$@% that just happens because someone does something stupid. (and we all have been there)

                  One thing that ASM also buys you from an o/s perspective, is ACFS. No need for a separate s/w stack and a separate cluster network config and heartbeat processing to run a shared cluster file system. So the pros are not only limited to the db instance side. And cons are few and very far in between IMO.
                  • 6. Re: Why are some DBA's averse to using ASM?
                    user4397602
                    We had to take into account other factors besides cost and simplicity :). We have experienced Unix admins who are loathe to consider Linux. Currently we have Veritas VCS clustering our DB servers on HP-UX and have had some issues with it due to way our Networking infrastructure is setup. AIX Virtualization on Power7 is robust, fast and scalable according to IBM! and we also have considerable experience with Power HA(HACMP) which has stood the test of times. As a DBA I'd rather have a simple x-86 HW stack running RAC on Linux with Dataguard for failover, but there are competing visions and the Unix guys won out. Also to consider are the exorbitant Oracle Enterprise/RAC licensing costs. We are estimating that we'll cut the # of Oracle licenses by half going to Power. If Power 7+ comes out with higher speed late this year it will be even better.

                    Edited by: user4397602 on Jun 20, 2012 9:58 AM
                    • 7. Re: Why are some DBA's averse to using ASM?
                      jgarry
                      EdStevens wrote:
                      user4397602 wrote:
                      We are upgrading to 11GR2 from 10G and are looking at the pros and cons of using ASM vs AIX JFS2. We are currently on HP-UX on Itanium and it's easy to guess why we are considering moving to AIX.
                      <snip>

                      Just an aside comment ... it's easy to guess why you are leaving Itanium, but not so easy o guess why moving to AIX. It has some quirks of its own, and you are still paying for dedicated hardware software. why not move to Oracle Linux on commodity hardware? No, I'm not a sales guy, and have not vested interest. But given that Linux is all but free and you can run it on generic hardware, the cost argument is pretty compelling. As for the technical merits of AIX, I've used it and have no complaints, but it is surprising how often the oracle docs have to include side notes pointing out special considerations for AIX vs. any other *nix.
                      Mladen and Noons have an interesting perspective on that in this [url http://groups.google.com/group/comp.databases.oracle.server/browse_thread/thread/b75a266d1b9d24eb/c6b71e096968a2cd#c6b71e096968a2cd]usenet thread. RAC v. non-RAC and editions skew the cost argument, to put it mildly.

                      I was saying back in the '90s that AIX seemed more idiosyncratic than other unix, and I still think that is both good and bad. I think it was the 7.1 timeframe the AIX specific Oracle guide was far superior to the other platform manuals (at the time, I had numerous platform manuals on the shelf next to me, it made it obvious). I think I'd like to go there like the OP, though some of the apps under consideration make me worry it will be the same old 4GL nonsense, er, issues.
                      • 8. Re: Why are some DBA's averse to using ASM?
                        user4397602
                        Billy, I have read a lot of your posts about ASM and am glad you responded. From reading up on ASM, I think the only situation where cooked fs would fare better is when using SAN snapshots. I currently have multiple Development databases(copies of Prod) sharing a host and I can snap the prod luns and mount them to any Dev database (all have individual luns similar to prod) in minutes quite easily. With the Oracle recommendation of only 2 DG's per ASM instance this will be impossible to do. If I can have a separate DG for each database I believe the snapshots will work for me. Your comments are appreciated.

                        Edited by: user4397602 on Jun 20, 2012 10:06 AM

                        Edited by: user4397602 on Jun 20, 2012 10:10 AM
                        • 9. Re: Why are some DBA's averse to using ASM?
                          EdStevens
                          user4397602 wrote:
                          We had to take into account other factors besides cost and simplicity :).
                          Fair enough.
                          We have experienced Unix admins who are loathe to consider Linux.
                          Ah yes. Never underestimate the power of ... I'm not sure exactly what to call it. I know the decision has been made (and given other considerations, it may very well have been a good decision) and I'm preaching to the choir, but for the record .... I know that some purists don't consider "linux" to be "unix", but I really don't see any difference between Linux and some-generic-linux than I do between the various actual versions of unix I've worked with -- Solaris, HP-UX, and AIX. Once you are familiar with one, moving to another should be no big deal from an admin/learning standpoint. If a *nix admin digs in his heels at the thought of learning another flavor, one would almost have to question his real motives ... and real expertise.  Is he good because he's good (intelligent, thoughful, adaptive, good analysis and problem solving skills and aptitude), or because he's been doing the same thing the same way for years.....

                          I wonder what their reaction would be if the suits told them the choice was Linux or .... Windows !!.

                          Again, I preach to the choir.
                          Currently we have Veritas VCS clustering our DB servers on HP-UX and have had some issues with it due to way our Networking infrastructure is setup. AIX Virtualization on Power7 is robust, fast and scalable according to IBM! and we also have considerable experience with Power HA(HACMP) which has stood the test of times. As a DBA I'd rather have a simple x-86 HW stack running RAC on Linux with Dataguard for failover, but there are competing visions and the Unix guys won out. Also to consider are the exorbitant Oracle Enterprise/RAC licensing costs. We are estimating that we'll cut the # of Oracle licenses by half going to Power. If Power 7+ comes out with higher speed late this year it will be even better.

                          Edited by: user4397602 on Jun 20, 2012 9:58 AM
                          • 10. Re: Why are some DBA's averse to using ASM?
                            Billy~Verreynne
                            user4397602 wrote:

                            With the Oracle recommendation of only 2 DG's per ASM instance this will be impossible to do.
                            Do you have a doc ref or URL to share where Oracle states that? Cannot recall ever reading any such recommendation. And I have a couple of RACs using ASM with 2+ diskgroups. Even one where diskgroups are across very different I/O fabric layers (Infiniband and Fibre Channel) and used in the same ASM instances by the same RAC db instances.

                            According to the ASM manual, the limits are 63 diskgroups in a storage system, 10,000 disks, 4PB per disk, 40 Exatabyte in total, with a million files per diskgroup.
                            • 11. Re: Why are some DBA's averse to using ASM?
                              Billy~Verreynne
                              user4397602 wrote:

                              .. but there are competing visions and the Unix guys won out.
                              It is weird to see the views that some have of Linux.

                              A while back, Oracle asked me to chat RAC to one of the local banks as they were hitting the scalability ceiling with their current (non RAC) architecture. And the customer wanted to know about RAC from another customer, rather than from Oracle sales and marketing.

                              I explained the architecture and then went into detail about the various components that made up our RAC clusters. When I mentioned that we only use Linux (and have been for many years), I got stunned wtf looks. Linux was seen as... well, not sure what exactly, but definitely as inferior to HP-UX, AIX and Solaris. Something that a banking system can never run on.

                              This turned to shock looks when I told them that the inferiority is the other way around and that over 90% of the world fastest 500 computing clusters run Linux.. and not Solaris, AIX or HP-UX. So why should we built clusters on anything than robust, mature and proven o/s technology?

                              Through the years I've used IRIX, SINIX, SCO, HP-UX and Solaris. From running mainframe gateways, GIS products and database s/w, to rolling production code using C. I prefer Linux above all these. It is simply that damn good.

                              Your Unix guys are doing, IMO, serious damage to your company's infrastructure ito TCO, flexibility, robustness, and performance - with their ignorant view of Linux.
                              • 12. Re: Why are some DBA's averse to using ASM?
                                user4397602
                                Thanks agian Billy. Here's the Oracle 10G ASM best practices doc that states that - Page 13. I couldn't find a 11G ASM doc.

                                [http://www.oracle.com/technetwork/database/asm-10gr2-bestpractices.pdf]

                                "To reduce the complexity of managing ASM and its diskgroups, Oracle recommends that generally no
                                more than two diskgroups be maintained and managed per RAC cluster or single ASM instance
                                10"

                                Also in this PPT by Nitin Vengurlekar who has a book on ASM, Page 13 states that as well
                                [http://www.dbaexpert.com/blog/wp-content/uploads/2009/08/doug-top-10-asm-questions.pdf]
                                • 13. Re: Why are some DBA's averse to using ASM?
                                  Billy~Verreynne
                                  Thanks for the references. I would like to see these statements backed up by something more than the vague reference that "+to reduce the complexity of managing ASM and its diskgroups+".

                                  ASM DG meta data resides in the disk header. One DG has not bearing on another - does not make another DG more complex to administer.

                                  I think that this recommendation is with reference to what is best for the database. Not ASM.

                                  Dealing, from a database instance, with multiple diskgroups is complex. There is only a single DB_CREATE_FILE_DEST parameter - and it can reference a single DG only. As that PDF presentation states:
                                  "+Having one DATA container means only place to store all your database files, and obviates the need to juggle around datafiles or having to decide where to place a new tablespace.+".

                                  This is not an ASM issue. It is a database storage one.

                                  But keep in mind that ASM is not only used for db storage. You may want two DG's for your database. Another DG for ACFS. And one more as a DG for RMAN hot backups (where this DG is for example an ASM mirror across 2 storage arrays).

                                  So I think one needs to see that recommendation within the context of "+what is recommended for a db instance+"

                                  We for example have a growing dev cluster (started off as 3 nodes, currently 9, with 3+ more nodes planned to be added). We use policy managed RAC databases. Currently it runs 3 RAC databases (4 nodes, 3 nodes and 2 nodes) - and with policy managed I can easily decrease the nodes for one RAC db and increase it for another RAC db. 2 (mostly self built) storage arrays (max 24TB each) are used.

                                  So keeping with the recommendation of 2 DGs per RAC db, I will need to run 6 DGs on an ASM instance, with 2 DGs being used by the local RAC instance. Not that I do - I have it set up as a single DG per RAC db (it is mostly dev, PoC and R&D environments). I agree with limiting the DGs for a database - but I do not see that limitation making much sense when dealing with ASM itself.
                                  • 14. Re: Why are some DBA's averse to using ASM?
                                    user4397602
                                    Thanks for all the useful info.

                                    About your earlier statement
                                    Billy  Verreynne  wrote:
                                    Your Unix guys are doing, IMO, serious damage to your company's infrastructure ito TCO, flexibility, robustness, and performance - with their ignorant view of Linux.
                                    I wouldn't be too harsh on Unix admins as I believe Unix still has a place in Data Centers. One of the reasons Admins like Unix and the Enterprise SPARC, Itanium and Power servers are the excellent RAS features provided by high end HW, and effectively used by Unix.

                                    One could make the same cost/benefit analysis and conclude that running SQL server on Vmware is significantly cheaper than Oracle on Linux. We have a quite a few Vmware on Xeon (4 Proc * 10 core = 40 core) servers. Running SQL Server on Xeon's is very fast, stable and cost effective as SQL licenses are much cheaper. Oracle DBA's obviously ought to ask if SQL can match Oracle. May be not, but SQL Server is a great option for certain requirements.

                                    We are looking at virtualization to consolidate Oracle databases on many servers into a few servers. If you want to run Oracle DB on Vmware you have to license all the cores on the server. Also with Oracle's vague support policy on Vmware, if you want to run Linux on a virtualized setup you have to go with Oracle VM as the only option. Running Oracle on a virtualized setup is what we are looking for and there are not may supported options for the enterprise other than Oracle VM (Sparc/X86) and IBM Power VM(AIX), and with our prior experience using AIX it came out as a good option.

                                    You either go the RAC route paying Oracle or go high end scalable virtualization paying Oracle, IBM or HP. Man! Oracle is everywhere!
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