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Storage System Environment

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  1. Storage System Environment Module 1.2

  2. Storage System Environment Upon completion of this module, 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 Storage System Environment

  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 Storage System Environment

  4. Group of Servers LAN 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) Server Laptop Mainframe Storage System Environment

  5. Host Applications Operating System File System DBMS Volume Manager Device Drivers HBA HBA HBA Host: Logical Components Storage System Environment


  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 Storage System Environment

  7. Logical Components of the Host (Cont) • Device Drivers • Enables operating system to recognize the device • Provides APIto 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 Storage System Environment

  8. UNIX (UFS) File type and permissions Number of links Owner and group IDs Number of bytes in the file Last file access Last file modification Windows (NTFS) Time stamp and link count File name Access rights File data Index information Volume information File System: Metadata Examples Storage System Environment

  9. File Systems: Journaling and Logging • Improves data integrity and system restart time over non-journaling file systems. • Uses a separate area called a log or journal. • May hold all data to be written • May hold only metadata • Disadvantage - slower than other file systems. • Each file system update requires at least 1 extra write – to the log Storage System Environment

  10. Logical Storage LVM Physical Storage 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 Storage System Environment

  11. 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 Volume Logical Disk Block Logical Volume Physical Volume 1 Physical Volume 3 Physical Volume 2 Physical Disk Block Volume Group Storage System Environment

  12. LVM Example: Partitioning and Concatenation Servers Logical Volume Physical Volume Partitioning Concatenation Storage System Environment

  13. LVM Example A Windows XP system with two physical hard disks. • "C:", "D:", and "E:" are volumes. • Hard Disk 1 and Hard Disk 2 are physical disks. • Any of these can be called a "drive". Storage System Environment

  14. File System Blocks Teacher (User) Course File(s) File System Files 1 2 3 Configures/ Reside in Mapped by a file Manages system to Disk Physical Extents Disk Sectors LVM Logical Extents 5 4 6 Managed by Consisting of Mapped by Residing in disk storage LVM to subsystem How Files are Moved to and from Storage Storage System Environment

  15. CPU HBA Cable BUS Disk Port Connectivity • Interconnection between hosts or between a host and any storage devices • Physical Components of Connectivity are: • Bus, port and cable Storage System Environment

  16. Bus Technology Serial Serial Bi-directional Parallel Storage System Environment

  17. Bus Technology • System Bus – connects CPU to Memory • Local (I/O) Bus – carries data to/from peripheral devices. • Bus width measured in bits • Bus speed measured in MHz • Throughput measured in MB/S Storage System Environment

  18. DirectlyAttachedEntities Network ConnectedEntities Tightly ConnectedEntities 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) Storage System Environment

  19. 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 Storage System Environment

  20. PCI Storage System Environment

  21. 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) Storage System Environment

  22. PATA Storage System Environment

  23. SATA Storage System Environment

  24. 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) Storage System Environment

  25. SCSI-Bus Interface Connector N (Narrow) W (Wide) SCA (Single Connector Attached) Storage System Environment

  26. Pros: Fast transfer speeds, up to 320 megabytes per second Reliable, durable components Can connect many devices with a single bus, more than just HDs SCSI host cards can be put in almost any system Full backwards compatibility Cons: Configuration and setup specific to one computer Unlike IDE, few BIOS support the standard Overwhelming number of variations in the standard, hardware, and connectors No common software interfaces and protocol SCSI - Pros and Cons Storage System Environment

  27. Comparison IDE/ATA vs SCSI Feature IDE/ATA SCSI Internal and External Storage Connectivity Market Internal Storage 320 Speed (MB/sec) 100/133/150 Yes Hot Pluggable No Very good but veryexpensive to set up Expandability Easier to set up High cost/Fasttransfer speed Cost/Performance Good Storage System Environment

  28. 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 Storage System Environment

  29. 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 Storage System Environment

  30. 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 Storage System Environment

  31. Controller HDA Interface Power Connector Disk Drive Components Storage System Environment

  32. Physical Disk Structure Spindle Sector Track Sector Cylinder Track Platter Storage System Environment

  33. Block 0 (Upper Surface) Block 8 (Lower Surface) Block 16 Block 48 Block 32 Logical Block Address= Block# Logical Block Addressing Sector 10 Head 0 Cylinder 2 Physical Address= CHS Storage System Environment

  34. Platter Geometry and Zoned-Bit Recording Sector Track Platter Without Zones Platter With Zones Storage System Environment

  35. 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 Storage System Environment

  36. 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 Storage System Environment

  37. 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 Storage System Environment

  38. Buffer Interface HBA 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 External transfer rate measured here Internal transfer rate measured here Head Disk Assembly Disk Drive Storage System Environment

  39. SATA vs SAS drives in 3.5-in form factor in 2006 Power Consumption Power consumed by the disk motor: Power  Diameter4.6 ×RPM2.8 × Number of platters Storage System Environment

  40. 6 5 4 3 1 2 I/O Queue Arrival I/O Processed I/O Request Controller 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 Storage System Environment

  41. 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= Rs /1–U) • Time spent by a request in a queue Rq = Rs U /(1–U) • Average queue size = U2 / (1–U) • Calculate the same with service time is doubled Knee of curve: disks at about 70% utilization Low Queue Size 0% Utilization 70% 100% Storage System Environment

  42. 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? Storage System Environment

  43. 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) Storage System Environment

  44. 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 Enterprise Flash Drives: A New Generation Drives Storage System Environment

  45. 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 Storage System Environment

  46. 10@15K Fibre Channeldrives 30@15K Fibre Channel drives 1@15K FibreChannel drive Response Time 1 Flash drive IO per second 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 Storage System Environment

  47. 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 Storage System Environment

  48. 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 Storage System Environment

  49. Module Summary Key points covered in this module: • Storage system environment components: • Host, connectivity and storage • Physical disk structure and addressing • Factors affecting disk performance • Flash drives benefits Storage System Environment

  50. 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? Storage System Environment