Storage System Environment Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. Section 1 : Storage System Storage System Environment Chapter 2

Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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

Lesson: Components of Storage System Environment Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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

Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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 Group of Servers LAN Mainframe

Host: Logical Components Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. Host: Logical Components Host DBMS HBA Applications Volume Manager Operating System File System Device Drivers

Logical Components of the Host Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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 classified as: Block-level access: Data stored and retrieved in blocks, specifying the LBA (logical block address) 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

Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. Quiz Question Which statements is true? File-level access is a data stored and retrieved by specifying the name and path of files Applications runs on device manager Block-level access is a data stored and retrieved in blocks, specifying the logical block address File systems are resides between the applications and the hardware

Logical Components of the Host: LVM (Logical Volume Manager) Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. Logical Components of the Host: LVM (Logical Volume Manager) Provides a method for allocating space on mass-storage devices that is more flexible than conventional partitioning schemes. 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

Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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 Usually, Application and Operating System data is maintained in separate volume groups Logical Volume Logical Disk Block Logical Volume Physical Volume 1 Physical Volume 2 Physical Volume 3 Physical Disk Block Volume Group

LVM Example: Partitioning and Concatenation Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. LVM Example: Partitioning and Concatenation Servers Logical Volume Physical Volume Partitioning Concatenation

Logical Components of the Host (Cont) Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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 EXT2/3/4 Additional Task Research on Blade Server Technology & File Systems

How Files are Moved to and from Storage Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. How Files are Moved to and from Storage 1 2 3 4 5 6 Consisting of Mapped by LVM to Teacher (User) Course File(s) File System Files File System Blocks LVM Logical Extents Disk Physical Extents Disk Sectors Configures/ Manages Residing in Reside in Mapped by a file system to Managed by disk storage subsystem

Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. Connectivity Interconnection between hosts or between a host and any storage devices Physical Components of Connectivity are: Bus, port and cable CPU HBA Port Cable BUS Disk

Connectivity Protocol Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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/SATA) Network connected entities such as networked hosts, NAS or SAN (example SCSI or FC) Tightly Connected Entities Directly Attached Entities Network Connected Entities

Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. Quiz Question What is the use of Logical Volume Manager? Interconnection between hosts or between a host and any storage devices Tightly connected entities such as central processor to RAM, or storage buffers to controllers Responsible for creating and controlling host level logical storage Enables operating system to recognize the device

Popular Connectivity Options: PCI Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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 can support both 32-bit and 64-bit data bus Throughput depends on size of data bus and signal frequency: 133 MBps (32-bit at 33MHz) 266 MBps (32-bit at 66 MHz or 64-bit at 33 MHz) 533 MBps (64-bit at 66 MHz) PCI Express (PCIe) Enhanced version of PCI bus with higher throughput and clock speed Commonly used for graphics card

Popular Connectivity Options: IDE/ATA/SATA Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. Popular Connectivity Options: IDE/ATA/SATA 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 Has replaced ATA/IDE in most computers nowadays Hot-pluggable

Popular Connectivity Options: SCSI/SAS Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. Popular Connectivity Options: SCSI/SAS 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 Serial SCSI (SAS) Cheaper, simpler and provides higher performance than parallel SCSI Replaces parallel SCSI in servers nowadays

Storage: Medias and Options Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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

Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. Quiz Question What is the use of Logical Volume Manager? Interconnection between hosts or between a host and any storage devices Tightly connected entities such as central processor to RAM, or storage buffers to controllers Responsible for creating and controlling host level logical storage Enables operating system to recognize the device

Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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 Additional Task Research on various media technologies & their performance

Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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

Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. Disk Drive Components Interface Controller Power Connector HDD

Physical Disk Structure Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. Physical Disk Structure Spindle Sector Track Sector Cylinder Track Platter

Physical Disk Structure Data is recorded on tracks Concentric rings on the platter around the spindle Tracks are numbered, starting from 0, from the outer edge of the platter Track density measures how tightly the tracks are packed There are thousands of tracks on a single platter Tracks are divided into smaller units called sectors Most modern hard drives have 63 sectors per track A sector typically holds 512 bytes A cylinder is a set of identical tracks on both surfaces of each drive platter Location of drive head is referred to by cylinder number

Logical Block Addressing Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. Logical Block Addressing Sector 10 Block 48 Block 16 Block 32 Logical Block Address= Block# Block 0 Block 8 (Upper Surface) (Lower Surface) Head 0 Cylinder 2 Physical Address= CHS

Logical Block Addressing Earlier drives use physical address consisting of cylinder, head and sector (CHS) OS needs to be aware of disk geometry Logical block addressing (LBA) simplifies the disk addressing by using a linear address to access the physical blocks The disk controller translates LBA to CHS address OS only needs to know the number of blocks available Example 1: Say that a disk 8 sectors per track, 8 heads and 4 cylinders. In total, how many blocks are available? Example 2: If a sector holds 512 bytes, how many blocks are required for a 500GB hard disk?

Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. Quiz Question What is the use of Logical Volume Manager? Interconnection between hosts or between a host and any storage devices Tightly connected entities such as central processor to RAM, or storage buffers to controllers Responsible for creating and controlling host level logical storage Enables operating system to recognize the device

Disk Drive Performance Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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)

Disk Drive Performance: Seek Time Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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

Disk Drive Performance: Rotational Speed/Latency Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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

Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. Quiz Question What is the use of Logical Volume Manager? Interconnection between hosts or between a host and any storage devices Tightly connected entities such as central processor to RAM, or storage buffers to controllers Responsible for creating and controlling host level logical storage Enables operating system to recognize the device

Disk Drive Performance: Data Transfer Rate Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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 Buffer HBA Interface Head Disk Assembly Disk Drive

Fundamental Laws Governing Disk Performance Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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 6 5 4 3 I/O Controller Processed I/O Request Arrival I/O Queue

Fundamental Laws Governing Disk Performance Average inter-arrival time, Ra = 1 / a Average time between the arrival of the current I/O request to the arrival of the next I/O request Total response time, R = Rs / (1 – U) The time between the request arrival until the completion of I/O process Average queue size = U2 / (1 – U) Time spent by a request in queue = U x R

Utilization vs. Response time Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. Utilization vs. Response time Knee of curve: disks at about 70% utilization Low Queue Size 0% Utilization 70% 100% 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) Calculate the same with service time is doubled Additional Task Research on Disc Drive Technology

Application Requirements and Disk Performance Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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?

Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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) + 4KB/(40MB/s) = 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)

Application Requirements and Disk Performance Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. Application Requirements and Disk Performance Exercise: Consider an application that requires 2TB of storage capacity and performs 2600 IOPS Application I/O size is 2KB Specification of available disk drive: Drive capacity = 200GB 12000 RPM 5 ms average seek time 40 MB/sec transfer rate Calculate the number of disks required?

Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. Quiz Question What is the use of Logical Volume Manager? Interconnection between hosts or between a host and any storage devices Tightly connected entities such as central processor to RAM, or storage buffers to controllers Responsible for creating and controlling host level logical storage Enables operating system to recognize the device

Enterprise Flash Drives: A New Generation Drives Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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

Enterprise Flash Drives – Overview Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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

Enterprise Flash Drives – Benefits Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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

Enterprise Flash Drives – “Tier-0” Application Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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 Additional Task Research on Flash Drive Technology

Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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

Copyright © 2009 EMC Corporation. Do not Copy - All Rights Reserved. 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

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