STORAGE ARCHITECTURE/ MASTER): Disk Storage: What Are Your Options? Randy Kerns Senior Partner The Evaluator Group

Storage systems Types Markets Devices Characteristics Interfaces Form factor Importance Decisions Agenda

Types Different types for different markets  Cache-centric  Distributed  Clustered distributed  Open platform Different characteristics  Attachment: interface type, number, protocol  Functions  Cache Storage systems

Types Different characteristics (continued)  Device attachment Fibre channel – switched Fibre channel arbitrated loop FC to ATA with translator SAS – Serial Attached SCSI SCSI Storage systems (2)

Markets Enterprise datacenter  High-performance disk requirements  Lower performance data – secondary storage Small to mid-size business  Some high-performance disk requirements along with secondary storage  Lower performance disk may be adequate in many environments Departmental / workgroup  Some applications require high-performance disk  Many would be satisfied with lower performance disk Storage systems (3)

Characteristics Media – platters Rotation  Speed  Seek time Processor  Commands / data handling  Servo control  Cache buffer  Tagged command queuing Disk devices

Characteristics (continued) Reliability  Test time  Warranty  Disk aerobics Interfaces  Several types: Differences in capabilities  Number of interfaces  Serial or parallel Hot plug Distance CRC vs. parity Reliability / durability Devices (2)

Characteristics (continued) Offerings  Basically two types: Single processor to handle servo and command/data transfer  Typically slower RPM  Typically less reliability  Less cost Two processors  Highest performance  Highest reliability Devices (3)

Interfaces Fibre channel  High performance – hardware intensive implementation  Command queuing – typically to 256 depth  Dual ported Some overlap – single data transfer path Allows alternate path  Dual processor implementation Performance and reliability Added cost Devices (4)

Interfaces ATA – Advanced Technology Attachment (a.k.a. IDE – Integrated Drive Electronics)  Basic command set  Limited command queuing  Two types: Parallel and serial Parallel – 18 in. distance with 133 MB/s bandwidth Serial – 1 meter distance with 150 MB/s bandwidth  Uses single processor drive hardware  Single ported but may have multiplexor added to front end  Can plug into SAS connector and controller Devices (5)

Interfaces Fibre Attached Technology Adapted (FATA)  Fibre channel interface  Command queuing – typically to 256 depth  Dual ported Same as fibre channel  Uses single processor drive hardware  Advantages: Low cost (small cost increase over ATA) Higher availability Storage systems can treat the same as FC drives – access, error recovery, no translator needed Devices (6)

Interfaces Serial Attached SCSI (SAS)  High-performance serial interface 3 Gb/s bandwidth, 8 meter distance 128 devices attach with expander to 16,384  Command queuing – typically to 256 depth  Dual ported Some overlap – single data transfer path Allows alternate path  Dual processor implementation Performance and reliability at higher cost  Uses same connector as SATA Devices (7)

Devices (8) SAS RAID Controller SAS RAID Controller SATA Drive SAS Drive SAS Drive SAS Expanders SATA Drive Internal (PCI-Xs, PCI Express*, HyperTransport, etc.) or External (FC, iSCSI, Infiniband*, SAS, etc.) Wide Ports (typ. 4 wide) Edge expanders typ. enclosed in JBOD Fanout expander for large configurations 2 Port to single port adapter

Interfaces SCSI  High-performance parallel interface Bandwidth up to 320 MB/s Limited distance 15 possible devices on SCSI bus  Command queuing – typically to 256 depth  Some drives are dual ported  Dual processor implementation Performance and reliability at higher cost Devices (9)

Form Factor 3.5”  Ubiquitous today  Drive platters are usually 2.5” or 3.0” 2.5”  New, high-performance 2.5” drives becoming available  Already have lower capacity, performance drives  Will be product changeover to 2.5” from 3.5” Drive vendors stated direction Will happen over next year Remember change from 5.25 to 3.5 ? Big change in packaging (drive shelves) Devices (10)

Decisions Basic choice: performance and reliability vs. cost  Understand requirements  Understand attributes: number of accesses, type of access Biggest issue: Controlling data placement when different devices are used  Automatically with host software  Automatically in storage system  Manual operation Importance

0/0 What is the most important aspect for you? 1.Performance 2.Reliability 3.Cost 4.Other

Decision process Make informed decision Know your requirements Understand device characteristics – not just price Data placement and control should be the first thing to understand. Importance (2)