© 2009 EMC Corporation. All rights reserved. Host and Storage System Environment Chapter 2

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 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

© 2009 EMC Corporation. All rights reserved. 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

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 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

© 2009 EMC Corporation. All rights reserved. Components of a Host - 5 Storage Hierarchy – Speed and Cost Speed Slow Fast Cost HighLow Tape Optical disk Magnetic disk RAM L2 cache L1 cache CPU registers

© 2009 EMC Corporation. All rights reserved. Components of a Host - 6 I/O Devices Human interface – Keyboard – Mouse – Monitor Computer-computer interface – Network Interface Card (NIC) Computer-peripheral interface – USB (Universal Serial Bus) port – Host Bus Adapter (HBA)

© 2009 EMC Corporation. All rights reserved. Components of a Host - 7 Logical Components of a Host

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 8 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

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 9 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

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 10 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

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 11 LVM Example: Partitioning and Concatenation PartitioningConcatenation Logical Volume Physical Volume Servers

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 12 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

© 2009 EMC Corporation. All rights reserved. Components of a Host - 13 File System: Metadata Examples 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

© 2009 EMC Corporation. All rights reserved. Components of a Host - 14 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

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 15 How Files are Moved to and from Storage

© 2009 EMC Corporation. All rights reserved. Components of a Host - 16 Module Summary Key points covered in this module: Hosts typically have: – Hardware: CPU, memory, buses, disks, ports, and interfaces – Software: applications, operating systems, file systems, device drivers, volume managers Journaling enables: – very fast file system checks in the event of system crash – provides better integrity for file system structure HBAs are used to connect hosts to storage devices

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 17 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

© 2009 EMC Corporation. All rights reserved. Connectivity - 18 Bus Technology Serial Serial Bi-directional Parallel

© 2009 EMC Corporation. All rights reserved. Connectivity - 19 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

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 20 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

© 2009 EMC Corporation. All rights reserved. Connectivity - 21 Communication Protocols Host Apps Operating System PCI SCSI or IDE/ATA Device Drivers

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 22 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 V1: 250MB/s V2: 500 MB/s V3: 1 GB/s

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 23 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)

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 24 Popular Connectivity Options: SCSI Parallel SCSI (Small computer system interface) – Most popular hard disk interface for servers – Supports Plug and Play – 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)

© 2009 EMC Corporation. All rights reserved. Connectivity - 25 SCSI - Small Computer System Interface Most popular hard disk interface for servers Higher cost than IDE/ATA Supports multiple simultaneous data access Currently both parallel and serial forms Used primarily in higher end environments

© 2009 EMC Corporation. All rights reserved. Connectivity - 26 SCSI Model Target Initiator

© 2009 EMC Corporation. All rights reserved. Connectivity - 27 SCSI Model Target ID Initiator ID LUNs

© 2009 EMC Corporation. All rights reserved. Connectivity - 28 SCSI Addressing Initiator ID - a number from 0 to 15 with the most common value being 7. Target ID - a number from 0 to 15 LUN - a number that specifies a device addressable through a target. Initiator IDTarget ID LUN

© 2009 EMC Corporation. All rights reserved. Connectivity - 29 Disk Identifier - Addressing c0 – Controller/ Initiator/HBA Peripheral Controller t0 Target LUNs d0d1d2 Host Addressing – Controller – Target – LUN c0 t0 d0

© 2009 EMC Corporation. All rights reserved. Connectivity - 30 SCSI - Pros and Cons 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

© 2009 EMC Corporation. All rights reserved. Connectivity - 31 Comparison IDE/ATA vs. SCSI FeatureIDE/ATA SCSI Connectivity MarketInternal Storage Internal and External Storage Speed (MB/sec) 100/133/ Hot Pluggable No Yes Expandability Easier to set up Very good but very expensive to set up Cost/Performance Good High cost/Fast transfer speed

© 2009 EMC Corporation. All rights reserved. Connectivity - 32 Physical Components – Host with External Storage Bus Disk Cable Host Port HBA CPU

© 2009 EMC Corporation. All rights reserved. Connectivity - 33 Fibre Channel Storage Arrays Host Apps DBMSMgmt Utils File System LVM Multipathing Software Device Drivers HBA

© 2009 EMC Corporation. All rights reserved. Connectivity - 34 External Storage Interfaces – A Comparison SCSI – Limited distance – Limited device count – Usually limited to single initiator – Single-ported drives Fibre Channel – Greater distance – High device count in SANs – Multiple initiators – Dual-ported drives

© 2009 EMC Corporation. All rights reserved. Connectivity - 35 External Storage Interfaces – A Comparison iSCSI – Transport is over an IP network – SCSI Commands are exchanged over an IP network Fibre Channel over Ethernet – Tunnels fibre channel commands over IP

© 2009 EMC Corporation. All rights reserved. Connectivity - 36 Fibre Channel Connectivity Switches Storage Hosts

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 37 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

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 38 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

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 39 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 Laws governing disk drive performance Enterprise flash drive

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 40 Disk Drive Components Interface Controller Power Connector HDA

© 2009 EMC Corporation. All rights reserved. Physical Disks - 41 Disk Drive Components: Platters

© 2009 EMC Corporation. All rights reserved. Physical Disks - 42 Disk Drive Components: Spindle Spindle Platters

© 2009 EMC Corporation. All rights reserved. Physical Disks - 43 Disk Drive Components: Read/Write Heads

© 2009 EMC Corporation. All rights reserved. Physical Disks - 44 Disk Drive Components: Actuator Actuator Spindle

© 2009 EMC Corporation. All rights reserved. Physical Disks - 45 Physical Disk Structures: Actuator Arm Assembly Actuator R/W Head

© 2009 EMC Corporation. All rights reserved. Physical Disks - 46 Disk Drive Components: Controller Bottom View of Disk Drive HDA Controller Interface Power Connector

© 2009 EMC Corporation. All rights reserved. Physical Disks - 47 Physical Disk Structures: Sectors and Tracks Sector Track Platter

© 2009 EMC Corporation. All rights reserved. Physical Disks - 48 Platter Geometry and Zoned-Bit Recording Platter Without Zones Sector Track Platter With Zones

© 2009 EMC Corporation. All rights reserved. Physical Disks - 49 Physical Disk Structures: Cylinders Cylinder Tracks, Cylinders and Sectors

© 2009 EMC Corporation. All rights reserved. Physical Disks - 50 Logical Block Addressing Physical Address = CHSLogical Block Address = Block # Sector Cylinder Head Block 0 Block 16 Block 32 Block 48 Block 8 (lower surface)

© 2009 EMC Corporation. All rights reserved. Physical Disks - 51 Drive Partitioning and Concatenation A Concatenation - One Logical Volume Partitioning - Multiple Logical Volumes A B C D

© 2009 EMC Corporation. All rights reserved. Physical Disks - 52 Lesson Summary Key points covered in this lesson: Physical drives are made up of: – HDA Platters connected via a spindle Read/write heads which are positioned by an actuator – Controller Controls power, communication, positioning, and optimization Data is structured on a drive using tracks, sectors, and cylinders The geometry of a disk impacts how data is recorded on a platter

© 2009 EMC Corporation. All rights reserved. Physical Disks - 53 Lesson: Disk Drive Performance Upon completion of this lesson, you will be able to: Describe the factors that impact the performance of a drive Describe how drive reliability is measured

© 2009 EMC Corporation. All rights reserved. Physical Disks - 54 Disk Drive Performance: Positioning Seek time is the time for read/write heads to move between tracks Seek time specifications include: – Full stroke – Average – Track-to-track

© 2009 EMC Corporation. All rights reserved. Physical Disks - 55 Disk Drive Performance: Rotational Speed/Latency

© 2009 EMC Corporation. All rights reserved. Physical Disks - 56 Disk Drive Performance: Command Queuing Request 1 Request 2 Request 3 Request Request 1 Request 2 Request 3 Request Without Command Queuing With Command Queuing

© 2009 EMC Corporation. All rights reserved. Physical Disks - 57 Disk Drive Performance: Data Transfer Rate Interface Buffer HBA Disk Drive Internal transfer rate measured here External transfer rate measured here

© 2009 EMC Corporation. All rights reserved. Physical Disks - 58 Drive Reliability: MTBF Mean Time Between Failure Amount of time that one can anticipate a device to work before an incapacitating malfunction occurs – Based on averages – Measured in hours Determined by artificially aging the product

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 59 Fundamental Laws Governing Disk Performance Littles 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 I/O Controller Processed I/O Request Arrival I/O Queue

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 60 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%

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 61 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

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 62 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

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 63 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 Fibre Channel drive Fibre Channel drives Fibre Channel drives

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 64 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

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 65 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

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 66 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 – RPM – 5 ms average seek time – 40 MB/sec transfer rate Calculate the number of disks required?

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 67 Solution Calculate time required to perform one I/O Seek time + (rotational delay)/speed in RPM + (block size/transfer rate) Therefore, 5 ms / K/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)

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 68 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

© 2009 EMC Corporation. All rights reserved. Storage System Environment - 69 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?