Os concepts 5 Storage and IO Virtualization
- 1. Operating System Concepts: 5 Storage and IO Virtualization Prof Neeraj Bhargava Vaibhav Khanna Department of Computer Science School of Engineering and Systems Sciences Maharishi Dayanand Saraswati University Ajmer
- 2. Characteristics of Various Types of Storage Movement between levels of storage hierarchy can be explicit or implicit
- 3. Migration of data “A” from Disk to Register • Multitasking environments must be careful to use most recent value, no matter where it is stored in the storage hierarchy • Multiprocessor environment must provide cache coherency in hardware such that all CPUs have the most recent value in their cache • Distributed environment situation even more complex – Several copies of a datum can exist – Various solutions covered in Chapter 19
- 4. I/O Subsystem • One purpose of OS is to hide peculiarities of hardware devices from the user • I/O subsystem responsible for – Memory management of I/O including buffering (storing data temporarily while it is being transferred), caching (storing parts of data in faster storage for performance), spooling (the overlapping of output of one job with input of other jobs) – General device-driver interface – Drivers for specific hardware devices
- 5. Protection and Security • Protection – any mechanism for controlling access of processes or users to resources defined by the OS • Security – defense of the system against internal and external attacks – Huge range, including denial-of-service, worms, viruses, identity theft, theft of service • Systems generally first distinguish among users, to determine who can do what – User identities (user IDs, security IDs) include name and associated number, one per user – User ID then associated with all files, processes of that user to determine access control – Group identifier (group ID) allows set of users to be defined and controls managed, then also associated with each process, file – Privilege escalation allows user to change to effective ID with more rights
- 6. Virtualization • Allows operating systems to run applications within other OSes – Vast and growing industry • Emulation used when source CPU type different from target type (i.e. PowerPC to Intel x86) – Generally slowest method – When computer language not compiled to native code – Interpretation • Virtualization – OS natively compiled for CPU, running guest OSes also natively compiled – Consider VMware running WinXP guests, each running applications, all on native WinXP host OS – VMM (virtual machine Manager) provides virtualization services
- 7. Virtualization (cont.) • Use cases involve laptops and desktops running multiple OSes for exploration or compatibility – Apple laptop running Mac OS X host, Windows as a guest – Developing apps for multiple OSes without having multiple systems – QA testing applications without having multiple systems – Executing and managing compute environments within data centers • VMM can run natively, in which case they are also the host – There is no general purpose host then (VMware ESX and Citrix XenServer)
- 8. Computing Environments - Virtualization
- 9. Distributed Systems • Distributed computiing – Collection of separate, possibly heterogeneous, systems networked together • Network is a communications path, TCP/IP most common – Local Area Network (LAN) – Wide Area Network (WAN) – Metropolitan Area Network (MAN) – Personal Area Network (PAN) – Network Operating System provides features between systems across network • Communication scheme allows systems to exchange messages • Illusion of a single system