Compaq ProLiant 6000 Compaq DLT Tape Array II: High-Performance Backup of Ente - Page 6

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ECG075.0997 (cont.) DLT Tape Array II ... The dual peer-to-peer buses provide throughput that is superior to that of single PCI-buses typical of smaller servers. Many dual buses are stacked buses. They use a PCI-to-PCI-bridge, which feeds one PCI bus to the other and then goes through a host-to-PCI-bridge to get to the host bus (Figure 5). Although this permits the use of additional cards by providing more slots, it does not increase performance. In contrast, the additional PCI card space in the ProLiant 5000 and ProLiant 6000 permits use of multiple SMART-2/P Array Controllers, multiple SCSI cards for tape drives, and multiple network interface cards. All of these devices run at peak PCI speeds, coexisting with minimal bottlenecks in performance. Although the PCI bus is rated at 133 MB/second, that is a burst data transfer speed. Actual measurements are typically from 60 MB/second to a maximum sustained peak of about 100 MB/second. Host Bus Processors Host-to-PCI Bridge Memory PCI Bus Slots 133 MB/s PCI-to-PCI Bridge PCI Bus 133 MB/s Slots Figure 5: PCI-to-PCI bridge architecture. Feed Speed The disk drive subsystem is a critical component in high-speed backups. There is a direct relationship between the number of disk drives in the array and the speed at which the array can provide data to the processor (more drives allow greater speed). There is also a direct relationship between the number of RAID controllers and performance (more is better). For example, a server using a single SCSI card to access hard disks is limited to 10, 20 or 40 MB/s, depending on the type of SCSI cards and drives in use. On the other hand, an array controller can often deliver the maximum limit of performance that the PCI bus can deliver: 133 MB/s. The Compaq SMART-2/P Array Controller is the best choice. It has two channels, and a minimum of four drives per channel should be used for high performance. If only six drives are available, the best performance will be achieved by assigning three drives to each channel. Adding a fourth drive to each channel improves performance significantly. Adding more than four drives per channel makes only a minor improvement in throughput, although it does add capacity. Tests were performed with an assortment of narrow and wide drives ranging in size from 2 to 9 gigabytes (GB). Superior performance was seen on the Compaq Fast-Wide 2 GB, 4 GB and 9 GB drives. See Test 12 for more information.

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7
%
(cont.)
DLT Tape Array II
ECG075.0997
The dual peer-to-peer buses provide throughput that is superior to that of single PCI-buses
typical of smaller servers. Many dual buses are stacked buses. They use a PCI-to-PCI-bridge,
which feeds one PCI bus to the other and then goes through a host-to-PCI-bridge to get to the
host bus (Figure 5). Although this permits the use of additional cards by providing more slots, it
does not increase performance. In contrast, the additional PCI card space in the ProLiant 5000
and ProLiant 6000 permits use of multiple SMART-2/P Array Controllers, multiple SCSI cards
for tape drives, and multiple network interface cards. All of these devices run at peak PCI
speeds, coexisting with minimal bottlenecks in performance. Although the PCI bus is rated at
133 MB/second, that is a burst data transfer speed. Actual measurements are typically from 60
MB/second to a maximum sustained peak of about 100 MB/second.
PCI-to-PCI
Bridge
Processors
Memory
Host Bus
Host-to-PCI
Bridge
PCI Bus
133 MB/s
PCI Bus
133 MB/s
Slots
Slots
Figure 5: PCI-to-PCI bridge architecture.
Feed Speed
The disk drive subsystem is a critical component in high-speed backups. There is a direct
relationship between the number of disk drives in the array and the speed at which the array can
provide data to the processor (more drives allow greater speed). There is also a direct
relationship between the number of RAID controllers and performance (more is better). For
example, a server using a single SCSI card to access hard disks is limited to 10, 20 or 40 MB/s,
depending on the type of SCSI cards and drives in use. On the other hand, an array controller
can often deliver the maximum limit of performance that the PCI bus can deliver: 133 MB/s.
The Compaq SMART-2/P Array Controller is the best choice. It has two channels, and a
minimum of four drives per channel should be used for high performance. If only six drives are
available, the best performance will be achieved by assigning three drives to each channel.
Adding a fourth drive to each channel improves performance significantly. Adding more than
four drives per channel makes only a minor improvement in throughput, although it does add
capacity.
Tests were performed with an assortment of narrow and wide drives ranging in size from 2 to 9
gigabytes (GB). Superior performance was seen on the Compaq Fast-Wide 2 GB, 4 GB and 9
GB drives. See Test 12 for more information.
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