1. ISDMR:BEIT VIII: CHAP2:MADHU N 1 ISM - Course Organization

2. ISDMR:BEIT VIII: CHAP2:MADHU N 2 Chapter Objectives Upon completion of this chapter, you will be able to: List components of storage system environment –Host, connectivity and storage List physical and logical components of hosts Describe key connectivity options Describe the physical disk structure Discuss factors affecting disk drive performance

3. ISDMR:BEIT VIII: CHAP2:MADHU N 3 Lesson: Components of Storage System Environment Upon completion of this lesson, you will be able to: Describe the three components of storage system environment –Host, Connectivity and Storage Detail Host physical and logical components Describe interface protocol –PCI, IDE/ATA and SCSI Describe storage options –Tape, optical and disk drives

4. ISDMR:BEIT VIII: CHAP2:MADHU N 4 Host Applications runs on hosts Hosts can range from simple laptops to complex server clusters Physical components of host –CPU –Storage Disk device and internal memory – I/O device Host to host communications –Network Interface Card (NIC) Host to storage device communications –Host Bus Adapter (HBA) Laptop Server Mainframe Group of Servers LAN

5. ISDMR:BEIT VIII: CHAP2:MADHU N 5 Host: Logical Components Host DBMS HBA Applications Volume Manager Operating System File System Device Drivers

6. ISDMR:BEIT VIII: CHAP2:MADHU N 6 Logical Components of the Host Application –Interface between user and the host –Three-tiered architecture Application UI, computing logic and underlying databases –Application data access can be classifies as: Block-level access: Data stored and retrieved in blocks, specifying the LBA File-level access: Data stored and retrieved by specifying the name and path of files Operating system –Resides between the applications and the hardware –Controls the environment

7. ISDMR:BEIT VIII: CHAP2:MADHU N 7 Logical Components of the Host: LVM Responsible for creating and controlling host level logical storage –Physical view of storage is converted to a logical view by mapping –Logical data blocks are mapped to physical data blocks Usually offered as part of the operating system or as third party host software LVM Components: –Physical Volumes –Volume Groups –Logical Volumes Physical Storage Logical Storage LVM

8. ISDMR:BEIT VIII: CHAP2:MADHU N 8 Volume Groups One or more Physical Volumes form a Volume Group LVM manages Volume Groups as a single entity Physical Volumes can be added and removed from a Volume Group as necessary Physical Volumes are typically divided into contiguous equal-sized disk blocks A host will always have at least one disk group for the Operating System –Application and Operating System data maintained in separate volume groups Logical Disk Block Volume Group Physical Disk Block Physical Volume 1 Physical Volume 2 Physical Volume 3 Logical Volume

9. ISDMR:BEIT VIII: CHAP2:MADHU N 9 LVM Example: Partitioning and Concatenation PartitioningConcatenation Logical Volume Physical Volume Servers

10. ISDMR:BEIT VIII: CHAP2:MADHU N 10 Logical Components of the Host (Cont) Device Drivers –Enables operating system to recognize the device –Provides API to access and control devices –Hardware dependent and operating system specific File System –File is a collection of related records or data stored as a unit –File system is hierarchical structure of files Examples: FAT 32, NTFS, UNIX FS and EXT2/3

11. ISDMR:BEIT VIII: CHAP2:MADHU N 11 How Files are Moved to and from Storage

12. ISDMR:BEIT VIII: CHAP2:MADHU N 12 Connectivity Interconnection between hosts or between a host and any storage devices Physical Components of Connectivity are: –Bus, port and cable CPUHBA Port Cable BUS Disk

13. ISDMR:BEIT VIII: CHAP2:MADHU N 13 Connectivity Protocol Protocol = a defined format for communication between sending and receiving devices –Tightly connected entities such as central processor to RAM, or storage buffers to controllers (example PCI) –Directly attached entities connected at moderate distances such as host to storage (example IDE/ATA) –Network connected entities such as networked hosts, NAS or SAN (example SCSI or FC) Tightly Connected Entities Directly Attached Entities Network Connected Entities

14. ISDMR:BEIT VIII: CHAP2:MADHU N 14 Popular Connectivity Options: PCI PCI is used for local bus system within a computer It is an interconnection between microprocessor and attached devices Has Plug and Play functionality PCI is 32/64 bit Throughput is 133 MB/sec PCI Express –Enhanced version of PCI bus with higher throughput and clock speed

15. ISDMR:BEIT VIII: CHAP2:MADHU N 15 Popular Connectivity Options: IDE/ATA Integrated Device Electronics (IDE) / Advanced Technology Attachment (ATA) –Most popular interface used with modern hard disks –Good performance at low cost –Inexpensive storage interconnect –Used for internal connectivity Serial Advanced Technology Attachment (SATA) –Serial version of the IDE /ATA specification –Hot-pluggable –Enhanced version of bus provides upto 6Gb/s (revision 3.0)

16. ISDMR:BEIT VIII: CHAP2:MADHU N 16 Popular Connectivity Options: SCSI Parallel SCSI (Small computer system interface) –Most popular hard disk interface for servers –Higher cost than IDE/ATA –Supports multiple simultaneous data access –Used primarily in “higher end” environments –SCSI Ultra provides data transfer speeds of 320 MB/s Serial SCSI –Supports data transfer rate of 3 Gb/s (SAS 300)

17. ISDMR:BEIT VIII: CHAP2:MADHU N 17 Storage: Medias and Options Magnetic Tape –Low cost solution for long term data storage –Limitations Sequential data access, Single application access at a time, Physical wear and tear and Storage/retrieval overheads Optical Disks –Popularly used as distribution medium in small, single-user computing environments –Write once and read many (WORM): CD-ROM, DVD-ROM –Limited in capacity and speed Disk Drive –Most popular storage medium with large storage capacity –Random read/write access Ideal for performance intensive online application

18. ISDMR:BEIT VIII: CHAP2:MADHU N 18 Lesson Summary Key points covered in this lesson: Host components –Physical and Logical Connectivity options –PCI, IDE/ATA, SCSI Storage options –Tape, optical and disk drive

19. ISDMR:BEIT VIII: CHAP2:MADHU N 19 Lesson: Disk Drive Upon completion of this lesson, you will be able to: List and discuss various disk drive components –Platter, spindle, read/write head and actuator arm assembly Discuss disk drive geometry Describe CHS and LBA addressing scheme Disk drive performance –Seek time, rotational latency and transfer rate Law’s governing disk drive performance Enterprise flash drive

20. ISDMR:BEIT VIII: CHAP2:MADHU N 20 Disk Drive Components Interface Controller Power Connector HDA

21. ISDMR:BEIT VIII: CHAP2:MADHU N 21 Physical Disk Structure Sector Track Platter Sector Track Cylinder Spindle

22. ISDMR:BEIT VIII: CHAP2:MADHU N 22 Logical Block Addressing Physical Address= CHS Cylinder 2 Head 0 Sector 10

23. ISDMR:BEIT VIII: CHAP2:MADHU N 23 Disk Drive Performance Electromechanical device –Impacts the overall performance of the storage system Disk Service Time –Time taken by a disk to complete an I/O request Seek Time Rotational Latency Data Transfer Rate Disk service time = Seek time + (rotational delay/speed in RPM)+ (block size/transfer rate)

24. ISDMR:BEIT VIII: CHAP2:MADHU N 24 Disk Drive Performance: Seek Time Time taken to position the read/write head Lower the seek time, the faster the I/O operation Seek time specifications include: –Full stroke –Average –Track-to-track

25. ISDMR:BEIT VIII: CHAP2:MADHU N 25 Disk Drive Performance: Rotational Speed/Latency The time taken by platter to rotate and position the data under the R/W head Depends on the rotation speed of the spindle Average rotational latency –One-half of the time taken for a full rotation –Appx. 5.5 ms for 5400-rpm drive –Appx. 2.0 ms for 15000- rpm drive

26. ISDMR:BEIT VIII: CHAP2:MADHU N 26 Disk Drive Performance: Data Transfer Rate Average amount of data per unit time Internal Transfer Rate –Speed at which data moves from a track to disk internal buffer External Transfer Rate –The advertised speed of the interface Interface Buffer HBA Disk Drive Internal transfer rate measured here External transfer rate measured here Head Disk Assembly

27. ISDMR:BEIT VIII: CHAP2:MADHU N 27 Fundamental Laws Governing Disk Performance Little’s Law –Describes the relationship between the number of requests in a queue and the response time. –N = a × R “N” is the total number of requests in the system “a” is the arrival rate “R” is the average response time Utilization law –Defines the I/O controller utilization –U = a × Rs “U” is the I/O controller utilization “RS“ is the service time 1 2 6543 I/O Controller Processed I/O Request Arrival I/O Queue

28. ISDMR:BEIT VIII: CHAP2:MADHU N 28 Utilization vs. Response time Consider a disk I/O system in which an I/O request arrives at a rate of 100 I/Os per second. The service time, RS, is 4 ms. –Utilization of I/O controller (U= a × Rs) –Total response time (R=R s /1-U) Calculate the same with service time is doubled 0%100%Utilization Knee of curve: disks at about 70% utilization Low Queue Size 70%

29. ISDMR:BEIT VIII: CHAP2:MADHU N 29 Enterprise Flash Drives: A New Generation Drives Conventional disk drive Mechanical Delay associated with conventional drive –Seek time –Rotational latency More power consumption due to mechanical operations Low Mean Time Between Failure Enterprise flash drive Highest possible throughput per drive –No Spinning magnetic media –No Mechanical movement which causes seek and latency –Solid State enables consistent I/O performance Very low latency per I/O Energy efficient storage design –Lower power requirement per GB of storage –Lower power requirement per IOPS

30. ISDMR:BEIT VIII: CHAP2:MADHU N 30 Enterprise Flash Drives – Overview Drive is based on Flash Solid State memory technology –High performance and low latency –Non volatile memory –Uses single layer cell (SLC) or Multi Level cell (MLC) to store data Enterprise Flash Drives use a 4Gb FC interface

31. ISDMR:BEIT VIII: CHAP2:MADHU N 31 Enterprise Flash Drives – Benefits Faster performance –Up to 30 times greater IOPS (benchmarked) –Typical applications: 8 – 12X –Less than 1 millisecond service time More energy efficient –38 percent less per terabyte –98 percent less per IO Better reliability –No moving parts –Faster RAID rebuilds IO per second Response Time 1 Flash drive 1@15K Fibre Channel drive 10@15K Fibre Channel drives 30@15K Fibre Channel drives

32. ISDMR:BEIT VIII: CHAP2:MADHU N 32 Enterprise Flash Drives – “Tier- 0” Application Position Enterprise Flash Drives as the high- performance option in demanding environments –Low latency applications, also known as “Tier-0” applications Standard form-factor and capacity design allows for easier integration High performance, low power for a “Green” initiative Target Customer/Market Segments: –High performance solutions coupled with low power –Specifically target Oracle database customers initially –Financial trading –OLTP databases

33. ISDMR:BEIT VIII: CHAP2:MADHU N 33 Lesson Summary Key points covered in this lesson: Disk drive components and geometry Disk drive addressing scheme Disk drive performance Convention drive Vs Enterprise Flash Drives Enterprise Flash Drives for high performance and low power storage solution

34. ISDMR:BEIT VIII: CHAP2:MADHU N 34 Application Requirements and Disk Performance Exercise: Consider an application that requires 1TB of storage capacity and performs 4900 IOPS –Application I/O size is 4KB –As it is business critical application, response time must be within acceptable range Specification of available disk drive: –Drive capacity = 73 GB –15000 RPM –5 ms average seek time –40 MB/sec transfer rate Calculate the number of disks required?

35. ISDMR:BEIT VIII: CHAP2:MADHU N 35 Solution Calculate time required to perform one I/O =Seek time + (rotational delay/speed in RPM)+ (block size/transfer rate) Therefore, 5 ms + 0.5 /15000 + 4K/40MB = 7.1 msec Calculate max. number of IOPS a disk can perform –1 / 7.1 ms = 140 IOPS For acceptable response time disk controller utilization must be less than 70% –Therefore, 140 X 0.7 = 98 IOPS To meet application –Performance requirement we need 4900/98 i.e. 50 disk –Capacity requirement we need 1TB/ 73 GB i.e. 14 disk Disk required = max (capacity, performance)

36. ISDMR:BEIT VIII: CHAP2:MADHU N 36 Chapter Summary Key points covered in this chapter: Storage system environment components: –Host, connectivity and storage Physical disk structure and addressing Factors affecting disk performance Flash drives benefits

37. ISDMR:BEIT VIII: CHAP2:MADHU N 37 Check Your Knowledge What are some examples of hosts? What are the physical and logical components of a host? What are the common connectivity protocols used in computing environments? What is the difference between seek time and rotational latency? What is the difference between internal and external data transfer rates?