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HP Surestore Disk Array 12h HP SureStore E Disk Array FC60 Service Manual (A56 - Page 199

Cache read ahead prefetch, Table 23, Performance Impact of Configuration Settings cont'd

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Table 23 Performance Impact of Configuration Settings (cont'd) Setting: Cache read ahead (prefetch) Function: Sets the number of additional sequential blocks transferred into read cache each time a read I/O is performed. Read ahead can be set for each volume. Performance Impact: Read ahead can significantly improve read performance for sequential I/O transactions. When a read is performed, the specified number of additional blocks are also read into cache in anticipation of the host issuing a read request for that data. Because the data is in cache, the number of read hits increases, improving performance. Read ahead is useful only for sequential I/O profiles. Read ahead can be tuned by increasing the setting and monitoring the cache hit percentage. If the percentage improves, the setting can be increased again until no improvement in performance is seen. Managing Disk Array Capacity 199 Managing the Disk Array

Section	Page
1 Product Description	15
Product Description	16
Operating System Support	18
Management Tools	18
Features	18
High Availability	18
Scalable Storage Capacity	19
LED Status Monitoring	19
Disk Enclosure Components	20
Operation Features	22
Disk Enclosure SC10 Modules	24
Array Controller Enclosure Components	31
Front Cover	34
Controller Modules	35
Controller Fan Modules	37
Power Supply Modules	39
Power Supply Fan Module	40
Battery Backup Unit	42
Disk Array High Availability Features	45
RAID Technology	45
Disk Mirroring	45
Data Parity	46
Data Striping	47
RAID Levels	48
RAID Level Comparisons	55
Global Hot Spare Disks	59
Capacity Management Features	62
Volume Groups	62
Disk Groups	62
Disk Array Caching	63
Dynamic Capacity Expansion	64
2 Topology and Array Planning	65
Overview	66
Array Design Considerations	67
Array Hardware Configuration	67
RAID, Volume Groups, and Global Hot Spares	68
High Availability	69
Performance	69
Storage Capacity	71
Expanding Storage Capacity	71
Recommended Disk Array Configurations	73
Configuration Considerations	73
One Disk Enclosure Configuration	74
Two Disk Enclosure Configurations	76
Three Disk Enclosure Configurations	80
Four Disk Enclosure Configurations	84
Five Disk Enclosure Configurations	88
Six Disk Enclosure Configurations	92
Total Disk Array Capacity	96
For high-availability, one disk per SCSI channel is used as a global hot spare.	97
Topologies for Windows NT and Windows 2000	98
Non-High Availability Topologies	100
High Availability Topologies	104
3 Installation	111
Overview	112
Host System Requirements	113
Windows NT and Windows 2000	113
Site Requirements	114
Environmental Requirements	114
Electrical Requirements	114
Power Distribution Units (PDU/PDRU)	117
Installing PDUs	119
Recommended UPS Models	119
Installing the Disk Array FC60	122
Installing the Disk Enclosures	127
Step 1: Collect Required Tools	127
Step 2: Unpack the Product	127
Step 3: Install Mounting Rails	129
Step 4: Install the Disk Enclosure	129
Step 5: Install Disks and Fillers	133
Moving a Disk Enclosure from One Disk Array to Another	135
Installing the Controller	136
Step 1: Gather Required Tools	136
Step 2: Unpack the Product	136
Step 3: Install Mounting Rails	139
Step 4: Install the Controller Enclosure	139
Configuration Switches	142
Disk Enclosure (Tray) ID Switch	142
Disk Enclosure DIP Switch	142
Fibre Channel Host ID Address Setting	145
Attaching Power Cords	149
Attaching SCSI Cables and Configuring the Disk Enclosure Switches	153
Full-Bus Cabling and Switch Configuration	154
Split-Bus Switch and Cabling Configurations	157
Connecting the Fibre Channel Cables	162
Applying Power to the Disk Array	164
Verifying Disk Array Connection	172
Configuring the Disk Array	173
Windows NT and Windows 2000	173
Adding Disk Enclosures to Increase Capacity	174
General Rules for Adding Disk Enclosures to the Disk Array	174
Step 1. Plan the Expanded Configuration	175
Step 2. Backup All Disk Array Data	176
Step 3. Prepare the Disk Array for Shut Down	176
Step 4. Add the New Disk Enclosures	177
Step 5. Completing the Expansion	180
Capacity Expansion Example	182
4 Managing the Disk Array	187
Tools for Managing the Disk Array FC60	188
Managing Disk Array Capacity	189
Configuring Volumes	189
Selecting Disks for a Volume Group	189
Assigning Volume Group Ownership	193
Selecting a RAID Level	193
Global Hot Spares	194
Setting Stripe Segment Size	194
Evaluating Performance Impact	196
Adding Capacity to the Disk Array	200
Adding More Disk Modules	200
Adding Additional Disk Enclosures	201
Replacing Disk Modules with Higher Capacity Modules	201
Moving a Volume Group from One Disk Array to Another	203
Controller Firmware Components	204
5 Troubleshooting	207
Introduction	208
About Field Replaceable Units (FRUs)	209
Windows NT and Windows 2000 Troubleshooting Tools	210
Disk Array Installation/Troubleshooting Checklist	211
Power-Up Troubleshooting	213
Controller Enclosure Troubleshooting	215
Introduction	215
Controller Enclosure LEDs	216
Controller Status LEDs	218
Identifying Interface Problems	236
Controller Enclosure Troubleshooting	240
Controller Midplane Troubleshooting	247
Cooling System	251
Controller Fan Module	255
Controller Enclosure Power Supply Fan Module	258
Power System	260
Power Supply Module	267
Battery Harness	271
DC Power Harnesses	272
Power Interface Board	274
Master Troubleshooting Table	275
SureStore E Disk System SC10 Troubleshooting	281
Disk Enclosure LEDs	281
Isolating Causes	284
6 Removal and Replacement	287
Overview	288
Required Tools and Equipment	290
Disk Enclosure Modules	291
Disk Module or Filler Module	291
Disk Enclosure Fan Module	296
Disk Enclosure Power Supply Module	298
BCC Module Removal/Replacement	300
Internal Disk Enclosure Assemblies	304
Disk Enclosure SC10	304
Front Cover Door Removal/Replacement	308
Top Cover Removal/Replacement	310
Power Button Assembly Removal/Replacement	312
Backplane/Mezzanine Removal/Replacement	314
Disk Module Carrier Removal/Replacement	318
Controller Enclosure Modules	321
Front Cover Removal/Replacement	322
Controller Fan Module	323
Battery Backup Unit (BBU) Removal/Replacement	325
Power Supply Fan Module Removal/Replacement	328
Power Supply Module Removal/Replacement	330
Controller Module	332
SCSI Cables	338
MIA	340
Internal Controller Enclosure Assemblies	342
Controller Enclosure	342
DIMM/SIMM Memory Cards	346
Harness Cover Plate	349
DC Power Harnesses	350
Power Supply Cage/Midplane Assembly	352
Battery Harness	354
Controller Cage/ Midplane Assembly / Battery Harness	355
7 Reference / Legal / Regulatory	359
System Requirements	360
Host Systems	360
Supported Operating Systems	360
Fibre Channel Host Adapters	360
Models and Options	361
A5635A Controller Enclosure	361
A5636A Disk Enclosure SC10	363
Disk Array FC60 Upgrade and Add-On Products	364
PDU/PDRU Products	365
Replaceable Parts	366
A5635A Controller Enclosure Specifications	368
Dimensions:	368
Weight:	368
AC Power:	369
Heat Output:	369
Environmental Specifications	370
Acoustics	371
A5636A Disk Enclosure Specifications	372
Dimensions:	372
Weight:	372
AC Power:	373
DC Power Output:	373
Heat Output:	373
Environmental Specifications	374
Acoustics	375
Warranty and License Information	376
Hewlett-Packard Hardware Limited Warranty	378
Software Product Limited Warranty	378
Limitation of Warranty	379
Hewlett-Packard Software License Terms	381
Regulatory Compliance	384
Safety Certifications:	384
EMC Compliance	384
FCC Statements (USA Only)	385
IEC Statement (Worldwide)	385
CSA Statement (For Canada Only)	385
VCCI Statement (Japan)	386
Harmonics Conformance (Japan)	386
Class A Warning Statement (Taiwan)	386
Spécification ATI Classe A (France Seulement)	387
Product Noise Declaration (For Germany Only)	387
Geräuschemission (For Germany Only)	388

Match case Limit results 1 per page

Managing Disk Array Capacity

199

Managing the Disk Array

Setting:

Cache read ahead (prefetch)

Function:

Sets the number of additional sequential blocks transferred into read cache each time

a read I/O is performed. Read ahead can be set for each volume.

Performance Impact:

Read ahead can significantly improve read performance for sequential

I/O transactions. When a read is performed, the specified number of additional blocks are also

read into cache in anticipation of the host issuing a read request for that data. Because the data

is in cache, the number of read hits increases, improving performance. Read ahead is useful

only for sequential I/O profiles.

Read ahead can be tuned by increasing the setting and monitoring the cache hit percentage. If

the percentage improves, the setting can be increased again until no improvement in

performance is seen.

Table 23

Performance Impact of Configuration Settings (cont’d)