Choosing the Right Disk Technology in a High Availability Environment DRAFT Version 2.0, August 1996

DRAFT -- Revision 2.0
August 22, 1996Page 2
Table of Contents
INTRODUCTION ..................................................... 4
Disk Link Technology Comparisons ....................................... 5
HP-FL disk links ................................................. 5
SCSI disk links .................................................. 5
Fibre Channel .................................................. 6
Disk Link Comparisons ........................................... 7
Disk Technologies .................................................... 8
Standalone disk drives with LVM mirroring ............................ 9
High Availability Storage Systems ............................. 10
Mirrored JBODs and SCSI targets ............................ 12
Mirrored JBODS and on-line replacement ...................... 13
Advantages and disadvantages of standalone disks with LVM mirroring
.................................................. 14
Disk Arrays using RAID technology ................................. 14
HP-FL Disk Arrays......................................... 16
F/W SCSI Disk Arrays ...................................... 18
High Availability Disk Arrays ................................. 19
Advantages and Disadvantages of High Availability Disk Arrays (HADAs)
.................................................. 22
Disk Arrays with AutoRAID .................................. 23
Advantages and Disadvantages of AutoRAID Disk Arrays .......... 26
Symmetrix 3000 Series Integrated Cache Disk Arrays (ICDA) ....... 27
Advantages and Disadvantages of Symmetrix ICDAs ............. 29
Solid State Disks ............................................... 30
Advantages and disadvantages of solid state disks ............... 30
CAPACITY ......................................................... 31
PERFORMANCE COMPARISONS ...................................... 34
LVM versus non-LVM managed disks ............................... 35
Striping ....................................................... 35
Data Protection ................................................ 36
I/O Size ................................................. 36
Ratio of reads to writes .......................................... 37
Sequential versus random access .................................. 37
Failed mechanisms in RAID 3 or 5 configurations ...................... 37