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

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

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

4. 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)

5. 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)

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

7. 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)

8. 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)

9. 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)

10. 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)

11. 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)

12. 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)

13. 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

14. 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)

15. 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)

16. 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

17. 0/0 What is the most important aspect for you? 1.Performance 2.Reliability 3.Cost 4.Other

18. 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)