1. Virtualisation From the Bottom Up From storage to application

2. academy@ ® Introduction What do we mean by Virtualisation? –The abstraction of computer resources –Can be done at many levels: Server Virtualisation Desktop Virtualisation Resource Virtualisation –Virtual Memory –Virtual Networks –Virtual Storage –Clustering We will focus on Server and Storage

3. academy@ ® Why Bother??? Virtualised resources maximize efficient use of hardware Storage virtualisation –Uses storage more efficiently –Greatly increases flexibility - can provide snapshot and mirroring functionality to aid test, backup and DR objectives –Increases scalability Server virtualisation –Consolidates hardware –Provides business continuity protection –Re-host legacy applications –Streamline software test and development

4. academy@ ® What is Storage Virtualization? Separating the logical representation of storage from the physical storage components. –Creating a logical virtualization layer –A software representation of volume entities Separates the host view of storage from the physical storage configuration Creates another object that has the important/essential characteristics of the original –Transparent to Host I/O

5. academy@ ® Blocks on Disks Disk Virtualization –The disk is presented as groupings of logical blocks –Blocks are the logical storage objects that “exist” on a disk\volume Data is written to or read from blocks by OS –Data layout on disk is hidden Physically on cylinders, heads and sectors (C/H/S) Logically presented as blocks –No knowledge of C/H/S Technology has existed for many years –Implemented in disk firmware

6. academy@ ® Block Virtualization A LUN is presented to a host More efficient use of storage division or assembly Implementation: RAID Server Manager SAN Appliance ASSEMBLY of logical volumes

7. academy@ ® Block Virtualization DIVISION into logical volumes

8. academy@ ® Block Vs Disk Virtualization Logical Block Assignment Virtualization Layer Disk Virtualisation Block Virtualisation Physical Disks Logical Volumes Mapping tables

9. academy@ ® Traditional Virtualization The most common locations today are: On Host –On most systems Function of Volume Manager At storage sub system –In RAID Controller Optimised purpose built hardware –Virtual Block/disk devices are presented as LUNs (Logical Units) Physical configuration hidden Virtualisation in the SAN

10. academy@ ® Storage Virtualisation over the SAN Unix Server Windows Server SAN Fabric Hosts Storage Tape Library RAID System / JBODs Virtualization Layer

11. academy@ ® Example – LSI StoreAge SVM Standard RAIDs, JBODs & TapesSVM Servers DPMs LinuxWindowsSolaris Front End Zone Back End Zone

12. academy@ ® Split-Path Approach (SPAID) Processor executes all operations Higher latencies Limited performance Processor executes few operation Low latency High performance Standard PC-based Platform Split-Path Approach Control and exception I/Os (~5%) Soft-Path CPU Switch Subsystem Data I/O Operations (~95%) Soft-Path CPU Switch Subsystem All I/O Operations (100%)

13. academy@ ® Essential concept – pooled storage Pool 1 Pool 2 Pool 3

14. academy@ ® An Introduction to MultiView Used to create and manage snapshots of SVM volumes A snapshot is a full representation of a volume –without having to copy all the volume data –multiple copies of a volume can be maintained, without having the need to wait hours for a data copy, or using valuable storage capacity Two basic elements are Point-in-Times (PiTs) and Views When a Pit is created, the data in the volume it relates to is “frozen” against write access –Updates are redirected to a new temporary volume –A PiT is therefore a snapshot of a volume at a set time A View is pointer to a PiT and is seen as an independent volume

15. academy@ ® Point in Time (PiT) I/O FROZEN Source Volume R W X X 1 2 Temporary Volume 2 Temporary Volume 1 Point in Time + RR Working Volume =+

16. academy@ ® MultiView FROZEN TV 2 TV 1 PiT View (logical Volume) Pointer Only The view appears as a logical volume, but it is only a pointer to the original volume and PiT(s). Working Volume Source Volume Automatic TV = + +

17. academy@ ® What is Server Virtualisation? A technology that employs an abstraction layer between the operating system and the underlying physical hardware Hardware Layer Software Layer Abstraction Layer “Hypervisor”

18. academy@ ® The key benefits of server virtualisation Isolation –A virtual machine’s state is unaffected by the state of other virtual machines on the same physical hardware Encapsulation –The state of a virtual machine can be captured and files representing a virtual machine can be migrated Hardware-independence –Virtual hardware does not have to be identical to the underlying physical hardware

19. academy@ ® Types of Hypervisor Type 1 or Bare-Metal –Special software than runs directly on a given hardware platform. E.g. Xen / Virtual Iron or VMware ESX Hypervisor Hardware App OS App OS App OS

20. academy@ ® Types of Hypervisor Type 2 or Hosted –Software than runs on an existing operating system, e.g. Microsoft Virtual PC, VMware Server Hardware Hypervisor App OS App OS App OS Host OS

21. academy@ ® Approaches to Virtualisation The x86 architecture was not designed to be virtualised Certain privileged and sensitive instructions cannot be easily virtualised There are three main methods for dealing with these, non-virtualisable instructions –Full Virtualisation with Binary Translation –Paravirtualisation –Native Virtualisation

22. academy@ ® Privilege Levels Without Virtualisation

23. academy@ ® Privilege Levels With Binary Translation

24. academy@ ® Privilege Levels With Paravirtualisation

25. academy@ ® Privilege Levels With hardware-assist

26. academy@ ® Full Virtualisation with Binary Translation Replaces non-virtualisable instructions with new sequences that have the intended effect on the virtual hardware User-level code is executed directly on the hardware The guest OS is not aware that it is being virtualised Significant costs in complexity and run- time performance

27. academy@ ® Paravirtualisation Non-virtualisable instructions are replaced by hypercalls that communicate directly with the hypervisor Carries a lower virtualisation overhead than Full Virtualisation The guest OS requires modification Unmodified OS’s (e.g, Windows XP) cannot be virtualised

28. academy@ ® Native Virtualisation Sometimes called Hardware Assisted Virtualisation Requires Intel and AMD processors with new hardware-assist capabilities Binary translation is effectively done in hardware Very low virtualisation overhead The guest OS is not aware that it is being virtualised

29. academy@ ® Example – Virtual Iron Components –Hypervisor First software loaded when physical server boots Based on open-source Xen hypervisor Uses Native Virtualisation –Service Partition Second software loaded when physical server boots Manages virtual machine creation and configuration and all I/O –Virtualisation Manager Controls virtual machines through an agent on the service partition –Guest Operating Systems

30. academy@ ® Architecture

31. academy@ ® Virtual Storage