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Disk Array High Availability Features
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RAID 3 works well for single-task applications using large block I/Os. It is not a good
choice for transaction processing systems because the dedicated parity drive is a
performance bottleneck. Whenever data is written to a data disk, a write must also be
performed to the parity drive. On write operations, the parity disk can be written to four
times as often as any other disk module in the group.
RAID 5
RAID 5 uses parity to achieve data redundancy and disk striping to enhance performance.
Data and parity information is distributed across all the disks in the RAID 5 LUN. A RAID 5
LUN consists of three or more disks. For highest availability, the disks in a RAID 5 LUN
must be in different enclosures.
If a disk fails or becomes inaccessible, the disk array can dynamically reconstruct all user
data from the data and parity information on the remaining disks. When a failed disk is
replaced, the disk array automatically rebuilds the contents of the failed disk on the new
disk. The rebuilt LUN contains an exact replica of the information it would have contained
had the disk not failed.
Until a failed disk is replaced (or a rebuild on a global hot spare is completed), the LUN
operates in degraded mode. The LUN must now use the data and parity on the remaining
disks to recreate the content of the failed disk, which reduces performance. In addition,
while in degraded mode, the LUN is susceptible to the failure of the second disk. If a
second disk in the LUN fails while in degraded mode, parity can no longer be used and all
data on the LUN becomes inaccessible.
Figure 22
illustrates the distribution of user and parity data in a five-disk RAID 5 LUN. The
the stripe segment size is 8 blocks, and the stripe size is 40 blocks (8 blocks times 5 disks).
The disk block addresses in the stripe proceed sequentially from the first disk to the
second, third, fourth, and fifth, then back to the first, and so on.
Содержание Surestore Disk Array 12h - And FC60
Страница 16: ...16 ...
Страница 36: ...36 Array Controller Enclosure Components Figure 9 Controller Enclosure Front View ...
Страница 41: ...Array Controller Enclosure Components 41 Product Description Figure 13 Controller Fan Module ...
Страница 44: ...44 Array Controller Enclosure Components Figure 15 Power Supply Fan Module ...
Страница 68: ...68 Capacity Management Features ...
Страница 117: ...Topologies for HP UX 117 Topology and Array Planning Figure 39 High Availability Topology ...
Страница 122: ...122 Topologies for HP UX Figure 40 High Availability Distance and Capacity Topology ...
Страница 126: ...126 Topologies for HP UX Figure 41 Campus Topology ...
Страница 130: ...130 Topologies for HP UX Figure 43 Four Hosts Connected to Cascaded Switches ...
Страница 134: ...134 Topologies for Windows NT and Windows 2000 Figure 45 Four Host Single Hub Single Disk Array Non HA Topology ...
Страница 136: ...136 Topologies for Windows NT and Windows 2000 Figure 47 Four Host Single Switch Dual Disk Array Non HA Topology ...
Страница 138: ...138 Topologies for Windows NT and Windows 2000 Figure 48 Direct Connect Single Host Single Disk Array HA Topology ...
Страница 140: ...140 Topologies for Windows NT and Windows 2000 Figure 50 Four Host Dual Hub Dual Disk Array HA Topology ...
Страница 142: ...142 Topologies for Windows NT and Windows 2000 ...
Страница 158: ...158 Installing the Disk Array FC60 Figure 54 Enclosure EIA Positions for System E Racks ...
Страница 159: ...Installing the Disk Array FC60 159 Installation Figure 55 Enclosure EIA Positions for Legacy Cabinets ...
Страница 161: ...Installing the Disk Enclosures 161 Installation Figure 56 Disk Enclosure Contents ...
Страница 172: ...172 Installing the Controller Figure 62 Controller Enclosure Package Contents ...
Страница 174: ...174 Installing the Controller Figure 63 Mounting the Controller Enclosure ...
Страница 234: ...234 Adding Disk Enclosures to Increase Capacity ...
Страница 274: ...274 Managing the Disk Array Using SAM Unassigned disks selected as hot spares ...
Страница 345: ...HP UX Diagnostic Tools 345 5 HP UX DIAGNOSTIC TOOLS Overview 346 Support Tools Manager 347 ...
Страница 350: ...350 Support Tools Manager Figure 90 mstm Interface Main Window ...
Страница 358: ...358 Support Tools Manager ...
Страница 401: ...Controller Enclosure Modules 401 Removal and Replacement Figure 101 BBU Removal and Replacement ...
Страница 440: ...440 FCC Statements USA Only ...
Страница 466: ...466 Index ...