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SnapView Snapshot

SnapView Snapshot. Upon completion of this module, you should be able to: Describe SnapView Snapshot operations Configure and Manage SnapView Snapshots. SnapView Snapshots. Lesson 1: Theory and Operation. During this lesson the following topics are covered:

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SnapView Snapshot

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  1. SnapView Snapshot Upon completion of this module, you should be able to: Describe SnapView Snapshot operations Configure and Manage SnapView Snapshots SnapView Snapshot

  2. SnapView Snapshots Lesson 1: Theory and Operation During this lesson the following topics are covered: Purpose of SnapView Snapshot SnapView Snapshots requirements SnapView Snapshots managed objects SnapView Snapshots theory of operations SnapView Snapshot

  3. SnapView Snapshots • SnapView Snapshot - an instantaneous frozen virtual copy of a LUN on a storage system • Allows a secondary server to view a point-in-time copy of a source LUN • Snapshots are created instantly – no data is copied at creation time • Snapshot will not change UNLESS the user writes to it • Original view available by deactivating changed Snapshot • Virtual LUN • Not a real LUN - made up of pointers, original and saved blocks • Uses a copy on first write (COFW) mechanism • Requires a ‘save area’ – the Reserved LUN Pool SnapView Snapshot

  4. SnapView Snapshots Requirements SnapView Snapshot

  5. SnapView Snapshots Managed Objects • Source LUN • The LUN containing production data • SnapView Session • Process of defining the point-in-time designation • Invokes COFW activity for updates to the source LUN • Reserved LUN • Supports the pointer-based design of SnapView Snapshot • Used to save data chunks • SnapView Snapshot • The defined virtual LUN • Presented to the secondary host • Enables visibility into running sessions SnapView Snapshot

  6. SnapView Session • SnapView Session • COFW mechanism starts and ends with session • SnapView snapshot appears off-line until there is an active session • A multiple Source LUN session can be started consistently • SnapView Session name • Sessions should have significant names • Compatibility with admsnap – use alphanumerics, underscores • It’s case-sensitive! • Session consistent start • Holds I/O until session starts on all source LUNs • Fails if any source LUN fails • Does not allow other LUNs to be added to session SnapView Snapshot

  7. Copy on First Write • Allows efficient utilization of copy space • Uses a dedicated save area – the Reserved LUN Pool • Total capacity of Reserved LUN Pool LUNs is approximately 20% of total source LUN sizes • Saves original data chunks – once only • Chunks are a fixed size - 64 KB (128 blocks) • Chunks are saved when they’re modified for the first time • Allows consistent ‘point-in-time’ views of LUN(s) • Allows rollback to previous points in time SnapView Snapshot

  8. Reserved LUN Recommendations • Total number of Reserved LUNs is VNX model-dependent • Reserved LUNs may be of different sizes • No checking of size, disk type or RAID type when allocated • Use SAS drives with write-cache enabled LUNs • Thin LUNS cannot be used in the RLP • Create 2 RLs per Source LUN, each 10% of Source LUN size • Example • LUNs to be snapped: 10 GB, 20 GB, 30 GB, 100 GB • Average LUN size = 160 GB/4 = 40 GB • Make each Reserved LUN 4 GB in size • Make 8 Reserved LUNs SnapView Snapshot

  9. SnapView: Stopping Sessions • Sessions may be manually stopped by the user • SnapView Sessions are automatically stopped • If the Reserved LUN Pool fills (attempt to use too much disk space) • Stopping the SnapView Session • Removes all memory map entries associated with session • Reserved LUN Pool space is made available for reuse SnapView Snapshot

  10. Host I/O to a Source LUN • Three possible types of I/O to a source LUN • Read or write request with no active session • I/O passed to driver below in I/O stack • Read request with active session • I/O passed to driver below in I/O stack • Write request with an active session • If the original data is not already in the Reserved LUN Pool, Copy on First Write is performed • Original data read from source LUN • SnapView finds an unused area in the Reserved LUN Pool • Original data written to unused area in Reserved LUN Pool • Entry made in memory and on disk to indicate where original data is written • Write request passed to driver below in I/O stack • If the original data is already in the Reserved LUN Pool, the write request is passed to driver below in I/O stack SnapView Snapshot

  11. Host I/O to a Snapshot • Three possible types of I/O to a Snapshot • Read or write request with no active session is intercepted by the SnapView driver • I/O requests fail – drive appears off-line • Read request with an active session • Memory map consulted to determine if the data should be read from the Reserved LUN Pool or from the source LUN • Write request with an active session • Write requests are allowed; however, any data written to a Snapshot is not persistent beyond the end of the session • The memory map is consulted to determine if the original data has been written to the Reserved LUN Pool (i.e., COFW has already occurred) • If not, a new map entry is created, and the original data is written to the RLP. The new data is written to the Source LUN SnapView Snapshot

  12. SnapView Snapshot Theory of Operation Reserved LUN Pool Source LUN Production Server 1 Chunks A B C LUN 6 LUN 7 Continuous I/O LUN 8 LUN 9 1 Session 9AM Chunks Session 9AM is started 1 A B C Reserved LUN 6 is allocated Source LUN COFW is enabled 8AM 9AM SnapView Snapshot

  13. SnapView Snapshot Theory of Operation (continued) Production Server Reserved LUN Pool Source LUN Chunks R / W A B C LUN 6 LUN 7 LUN 8 LUN 9 Session 9AM Snapshot of Source LUN is created but not activated 2 2 Server B Snapshot of Source LUN is added to the Storage Group of Server B 3 A B C Chunks Not Ready 3 Snapshot of Source LUN 10AM SnapView Snapshot

  14. SnapView Snapshot Theory of Operation (continued) Production Server Reserved LUN Pool Source LUN Chunks R / W A B C LUN 6 LUN 7 LUN 8 LUN 9 Session 9AM Snapshot of Source LUN is activated 4 Session 9AM is allocated by Snapshot of Source LUN Server B 4 Virtual Source LUN (Snapshot of Source LUN) is made available (R / W) to Server B A B C A B C Chunks Chunks R / W Snapshot of Source LUN 11AM SnapView Snapshot

  15. SnapView Snapshot Theory of Operation (continued) Production Server Reserved LUN Pool Source LUN 5 C’ Chunks C R / W A B C 6 LUN 6 LUN 7 LUN 8 LUN 9 Session 9AM Production Server requests a change on Chunk “C” (COFW) 5 Server B Original Chunk “C” is copied to the Reserved LUN 6 allocated by Session 9AM 6 A B C Chunks R / W Snapshot of Source LUN 12PM SnapView Snapshot

  16. SnapView Snapshot Theory of Operation (continued) Production Server Reserved LUN Pool Source LUN Chunks C R / W A B C’ LUN 6 LUN 7 7 LUN 8 LUN 9 Session 9AM Session 9AM pointer uses the original Chunk ‘C” from Reserved LUN 6 7 Server B A B C Chunks R / W Snapshot of Source LUN 12PM SnapView Snapshot

  17. SnapView Snapshot Theory of Operation (continued) Production Server Reserved LUN Pool Source LUN 9 Chunks R / W B B’ C A B C’ LUN 7 LUN 6 LUN 8 LUN 9 Session 9AM Server B requests a change on Chunk “B” (COFW) 8 Original Chunk “B” is copied to the Reserved LUN 6 allocated by Session 9AM and then modified by the write 9 Server B B’ A B C ’ Chunks R / W 8 Snapshot of Source LUN 1PM SnapView Snapshot

  18. SnapView Snapshot Theory of Operation (continued) Production Server Reserved LUN Pool Source LUN Chunks R / W B B’ C A B C’ LUN 7 LUN 6 1 0 LUN 8 LUN 9 Session 9AM Session 9AM pointer uses Chunk B’ from Reserved LUN 6 1 0 Server B A B’ C Chunks R / W Snapshot of Source LUN 1PM SnapView Snapshot

  19. SnapView Snapshots Lesson 1: Summary During this lesson the following topics were covered: Purpose of SnapView Snapshot SnapView Snapshots requirements SnapView Snapshots managed objects SnapView Snapshots theory of operations SnapView Snapshot

  20. SnapView Snapshots Lesson 2: Configuring and Managing SnapViewSnapshots During this lesson the following topics are covered: Managing the Reserved LUN Pool Managing SnapView sessions and SnapView snapshots Configuring and managing SnapView sessions and SnapView snapshots with the Wizards SnapView Snapshot

  21. Reserved LUN Pool Management SnapView Snapshot

  22. Reserved LUN Pool LUNs – Free LUNs SnapView Snapshot

  23. Reserved LUN Pool – Allocated LUNs SnapView Snapshot

  24. Monitoring Reserved LUN Pool Usage Storage System > System > Monitoring and Alerts > SP Event Logs SnapView Snapshot

  25. SnapView Sessions SnapView Snapshot

  26. SnapView Session Properties Storage System > Data Protection > Snapshots > LUN Snapshots SnapView Snapshot

  27. SnapView Session – Start / Stop SnapView Snapshot

  28. SnapView Snapshot SnapView Snapshot

  29. Snapshot Session Rollback SnapView Snapshot

  30. Snapshot Session Rollback Properties SnapView Snapshot

  31. Snapshot Configuration Wizard SnapView Snapshot

  32. SnapView Snapshots Lesson 2: Summary During this lesson the following topics were covered: Managing SnapView snapshots and SnapView sessions Configuring and managing SnapView snapshots and sessions with the Snapshot Wizard SnapView Snapshot

  33. Summary Key points covered in this module: • SnapView Snapshot is an instantaneous frozen virtual copy of a LUN on a VNX storage system • SnapView Snapshot uses COFW technology • Snapshot Wizard can be used to Configuring and managing SnapView snapshots and sessions SnapView Snapshot

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