6 Replies Latest reply: Apr 10, 2013 3:43 PM by D Tej RSS

    ASM Stripping and Mirroring

    902332
      Hi all,

      While reading this asm concepts i most of the time i came across stripping and mirroring.

      But i am not getting clear idea about this stripping and mirroring.

      Could you please give me clear idea about this to understand this

      thanks for you help...
        • 1. Re: ASM Stripping and Mirroring
          sb92075
          899329 wrote:
          Hi all,

          While reading this asm concepts i most of the time i came across stripping and mirroring.

          But i am not getting clear idea about this stripping and mirroring.

          Could you please give me clear idea about this to understand this

          thanks for you help...
          since you seem unwilling or incapable to use GOOGLE yourself I am assisting by proving URL below

          http://www.lmgtfy.com/?q=disk+stripping+mirroring
          • 2. Re: ASM Stripping and Mirroring
            Catch-22
            What are you reading?

            Let's say you have a 30 MB file and 2 hard drives.

            Mirroring duplicates the data to provide data redundancy. If one disk fails, the other one can be used to retrieve the data. This works transparently, without user intervention.

            Disk 1: 30 MB
            Disk 2: 30 MB

            Stripping distributes the data accross storage media to increase the total storage capacity. There is no redundancy, if one disks fails, the file is lost and recover has to be performed from external backup. The storage is also not usable anymore if one disk member is lost.

            Disk 1: 15 MB
            Disk 2: 15 MB

            Besides storage capacity and data redundancy there are also performance aspects since multiple disks are involved. A mirror will typically provide increased read performance since data can be read from 2 drives, but write performance will be the same than writing data to a single drive. Stripping will provide better read and write performance as the workload is split over multiple hardware. Stripping and Mirroring is often combined but an expensive storage solution since you need to have a least 4 disks.

            Keep in mind that Oracle ASM provides data redundancy that seems similar to typical RAID 1 (mirroring) and 0 (stripping) solutions, but works fundamentally different. RAID works on the basis of disk data blocks. ASM woks on the basis of files and using the free disk space of disk failure groups. ASM can also provide a 2-way mirroring using 3 disks, in which case data is stored in a round robin fashion.
            • 3. Re: ASM Stripping and Mirroring
              Victor Armbrust
              Follow an article that explain RAID concepts.

              When using ASM, you can do the mirroring using NORMAL REDUNDANCY in ASM DISKGROUPS.


              Oracle x RAID - Best Practices
              http://www.google.com/translate?u=http%3A%2F%2Fvictor-dba.blogspot.com.br%2F2012%2F03%2Foracle-x-raid-melhores-praticas.html&langpair=pt%7cen&en=pt&en=utf8

              Victor
              • 4. Re: ASM Stripping and Mirroring
                onedbguru
                A good resource for ASM concepts is "Automatic Storage Management - Under-the-Hood"

                http://my.safaribooksonline.com/book/operating-systems-and-server-administration/storage-systems/9780071496070
                • 5. Re: ASM Stripping and Mirroring
                  941744
                  That was fun.. I really Enjoyed... ;)
                  • 6. Re: ASM Stripping and Mirroring
                    D Tej
                    ASM Stripping:

                    ASM stripes files across all the disks within the disk group thus increasing performance, each stripe is called an ‘allocation unit’. ASM offers two types of stripping which is dependent on the type of database file

                    Coarse Stripping which is used for datafile, archive logs (1MB stripes)
                    Fine Stripping which is     used for online redo logs, controlfile, flashback files(128KB stripes)


                    ASM Mirroring

                    Disk mirroring provides data redundancy, this means that if a disk were to fail Oracle will use the other mirrored disk and would continue as normal. Oracle mirrors at the extent level, so you have a primary extent and a mirrored extent. When a disk fails, ASM rebuilds the failed disk using mirrored extents from the other disks within the group, this may have a slight impact on performance as the rebuild takes place.

                    All disks that share a common controller are in what is called a failure group, you can ensure redundancy by mirroring disks on separate failure groups which in turn are on different controllers, ASM will ensure that the primary extent and the mirrored extent are not in the same failure group. When mirroring you must define failure groups otherwise the mirroring will not take place.

                    There are three forms of Mirroring

                    External redundancy - doesn't have failure groups and thus is effectively a no-mirroring strategy
                    Normal redundancy - provides two-way mirroring of all extents in a disk group, which result in two failure groups
                    High redundancy - provides three-way mirroring of all extents in a disk group, which result in three failure groups