7 Replies Latest reply on Sep 1, 2016 10:22 PM by Dude!

    1+0  Vs  0+1 in ASM

    Jhil

      RAID  0  for  Stripping

      RAID  1  for  Mirroring.

      Actually what is  1 + 0  and  0 +1  for ASM ?

      Are they talking about RAID conecepts in ASM ?

      Please accept my applogies , if my question is very silly.

      I dont undestand clearly. Please clarify.

       

       

       

       

       

        • 1. Re: 1+0  Vs  0+1 in ASM
          Pini Dibask

          Hello,

          955912 wrote:

           

          RAID 0 for Stripping

          RAID 1 for Mirroring.

          Actually what is 1 + 0 and 0 +1 for ASM ?

          Please refer to the following article regarding the differences between RAID 1+0 and RAID 0+1: http://www.thegeekstuff.com/2011/10/raid10-vs-raid01/

           

          Are they talking about RAID conecepts in ASM ?

          Please accept my applogies , if my question is very silly.

          I dont undestand clearly. Please clarify.

          Oracle ASM provides striping and mirroring capabilities that are similar to RAID 10; however, Oracle ASM doesn't behave exactly as RAID and it can be even smarter due to the fact that it's aware of the different Oracle Database file types. So it can stripe data differently for different file types, while traditional RAID stripes at the block level aren't aware of the different Oracle Database file types. Oracle ASM is also more flexible in terms of mirroring, because it allows different types of mirroring for different files. Read more about this in my article which review what exactly ASM is and how it is different than RAID: Verifying I/O Activity Balance Across Disks in ASM

          1 person found this helpful
          • 2. Re: 1+0  Vs  0+1 in ASM
            Dude!

            What ASM redundancy and RAID redundancy have in common is redundancy, but how it is accomplished is fundamentally different. Comparing RAID with ASM redundancy is comparing apples and oranges. ASM is not RAID. RAID redundancy mirrors complete disks. ASM uses file based redundancy, using free disk space available on any device that is a failgroup within the ASM diskgroup.

             

            ASM is much more flexible than RAID and knows specifically about Oracle database files to use appropriate strip sizes for best performance. You can also resize ASM diskgroups and add additional devices while the diskgroup is online. On the contrary, if you wish to reconfigure a RAID system, you would loose the existing data.

             

            You can however create ASM storage using RAID volumes for additional performance and redundancy, but it is a cost factor. Typically you would either use ASM (normal, high) or RAID redundancy (external). If you have a fake or software based RAID, as opposed to a real hardware RAID, you should probably opt for ASM instead. But then again, ASM was specifically designed to deal with Oracle database files.

            1 person found this helpful
            • 3. Re: 1+0  Vs  0+1 in ASM
              BPeaslandDBA

              If you want to have a choice between 0+1 or 1+0, then you need to perform the RAID level on the storage system itself. Then tell ASM that the diskgroup has external redundancy.


              Cheers,

              Brian

              • 4. Re: 1+0  Vs  0+1 in ASM
                Jhil

                Hi All,

                 

                Thanks all,

                Sorry to ask different question from ASM here.

                 

                # /etc/init.d/oracleasm status

                Checking if ASM is loaded: yes

                Checking if /dev/oracleasm is mounted: yes

                 

                # ls -l /dev/sd[b-g]1

                brw-r----- 1 root disk 8, 17 Sep  1 08:09 /dev/sdb1

                brw-r----- 1 root disk 8, 33 Sep  1 08:09 /dev/sdc1

                brw-r----- 1 root disk 8, 49 Sep  1 08:09 /dev/sdd1

                brw-r----- 1 root disk 8, 65 Sep  1 08:09 /dev/sde1

                brw-r----- 1 root disk 8, 81 Sep  1 08:09 /dev/sdf1

                brw-r----- 1 root disk 8, 97 Sep  1 08:09 /dev/sdg1

                 

                but why following command gets failed ?  Any reason ?

                 

                # ./oracleasm createdisk VOL1 /dev/sdb1

                Marking disk "VOL1" as an ASM disk:                        [FAILED]

                 

                Thanks

                 

                 

                EDIT

                 

                # oracleasm querydisk /dev/sd[b-g]1

                Device "/dev/sdb1" defines a device with no label

                Device "/dev/sdc1" defines a device with no label

                Device "/dev/sdd1" defines a device with no label

                Device "/dev/sde1" defines a device with no label

                Device "/dev/sdf1" defines a device with no label

                Device "/dev/sdg1" defines a device with no label

                • 5. Re: 1+0  Vs  0+1 in ASM
                  BPeaslandDBA

                  Did you use fdisk to format the device? The typical way I do that is:

                   

                  fdisk /dev/sdb

                  Then answer:

                  n       <- for new partition

                  p       <- primary partition

                  1       <- partition number 1

                  enter  <- start on first cylinder

                  enter  <- end on last cylinder

                  w        <- write changes

                   

                  Something to that effect.

                   

                  Cheers,
                  Brian

                  • 6. Re: 1+0  Vs  0+1 in ASM
                    Dude!

                    May I suggest you start a new thread regarding your second question, because it has nothing to do with the initial question asked here.

                    • 7. Re: 1+0  Vs  0+1 in ASM
                      Dude!

                      ASM can use devices with or without a partition, for example /dev/sdc or /dev/sdc1. However using a partition is recommended, otherwise it will be less clear what devices from a device pool are in use and which are not. I think the problem is rather incorrect device permissions, preventing ASMlib from instantiating the device.

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