ABB 模块TB840A
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嵌入式存储交换技术还是比较常用的，于是我研究了一下如何增加嵌入式存储交换技术的可靠性，在这里拿出来和大家分享一下，希望对大家有用。嵌入式存储交换技术使存储系统可以在存储阵列内部集成2Gbps交换网络连接。嵌入式存储交换技术的好处包括更高的可靠性、更好的性能以及在不降低性能的条件下添加硬盘的能力。
共享总线架构被应用在许多存储系统的后端，从而使存储阵列中的每一个硬盘驱动器或磁带驱动器成为一个单故障点。由于一个驱动器出现问题而大大增加了整个磁盘阵列停机的风险。存储区域网或网络连接存储系统的前端无论是否使用光纤通道、iSCSI或IP，存储系统控制器都利用原始的光纤通道仲裁回路(FC-AL)共享总线协议，对前端发送到后端的请求进行翻译。老式FC-AL环路的仲裁和数据流必须经过环路中的所有设备。因此，这条路径上的每一台设备都增加了时延，更重要的是，增加了额外的故障点。
老式FC-AL环路通过控制器机制运行，控制器首先对环路的控制权进行仲裁，然后向一个硬盘驱动器发送命令，要求驱动器接收写到硬盘上的数据或从特***置请求数据。而后端嵌入式存储交换技术以交换的方式使用FC-AL协议，将点到点连接赋予每个磁盘驱动器。
交换机如果采用嵌入式存储交换技术，那么它的芯片上将集成交换机内核、嵌入式并串转换器/串并转换器、1G/2Gbps带宽功能和诊断功能的关键部件。存储系统在物理上将多块硬盘安装在一个机箱中，构成所谓的“硬盘组”(JBOD)。在嵌入式存储交换机提供的更高水平的集成出现之前，由于空间、电源、热量和价格问题，在JBOD中安装交换功能对于模块化存储系统是不切实际的。在嵌入式存储交换添加到JBOD时，它就变成了交换硬盘组(SBOD)。
现在当一个发起设备对系统的控制权进行仲裁时，仲裁进程不经过所有的设备(如在共享总线架构中)，而只传送到交换矩阵并返回给发起设备。这个过程非常快，大大减少了系统时延。在发起设备获得控制权后，它可以打开目标驱动器并开始通信。发起设备与驱动器之间传送的数据包现在是点到点传送的，并且多个对话可以同时发生。
无论嵌入式后端交换机是提供从控制器到多部JBOD的连接性，还是提供到使用SBOD的单个硬盘驱动器的连接性，嵌入式交换都实现了连接的可靠性、可用性和适用性。嵌入式交换为IT管理人员提供了部署自动维护、监控和维修的工具。每一个嵌入存储交换机端口都可以重新调整低电平信号时间，从而增加信号的完整性，减少系统抖动。
IT管理人员可以在***高层面上制定策略，这些策略可以传送到存储系统的***低层，而后端嵌入式存储交换机则可以在***低层上执行这些策略。例如，可以制定一项策略，规定当检测到故障趋势时(如一段时间上循环冗余校验错误数量增多)自动删除硬盘。
嵌入式存储交换技术消除了共享基础设施存储系统运行时造成的性能瓶颈。目前所有的拓扑结构都可以从后端交换技术的某个方面受益(在后端嵌入式存储交换技术中，性能将根据负载分布(从视频流到数据仓库应用)的不同而变化)，更能从存储系统的低拥有成本和自动化中受益。
***F SVENSKA MANOMETER 0-4000 BAR 6-1/4 IN DIAL 3/8 IN N
DWYER 2002 MAGNEHELIC 0-2IN-H2O 4 IN 1/8 IN NPT PRESSUR
NEW ASHCROFT 25W1001TH PRESSURE 0-200PSI 2-1/2 IN 1/4 I
WEKSLER INSTRUMENTS ROYAL SERIES PRESSURE 0-160PSI 4-1
ASHCROFT Q-586 DURAGAUGE PRESSURE 0-160PSI 5IN FACE DIA
BOURDON PRESSURE 0-100PSI 4 IN 1/4 IN NPT GAUGE B302778
ASHCROFT TWIN NEEDLE PRESSURE 0-60PSI 5-1/2 IN GAUGE B2
WIKA 0-5000PSI 1-1/2IN 0-30000KPA 1/8IN NPT STAINLESS P
NEW ASHCROFT 351009AW02L PRESSURE 0-300PSI 3-1/2 IN 1/4
DWYER 2002C MAGNEHELIC PRESSURE 0-2IN-H2O 4IN DIAL FACE
NEW WIKA PRESSURE 0-100PSI 2-3/8 IN 1/4 IN NPT GAUGE D2
DWYER 2002C MAGNEHELIC 0-2IN-H2O 4 IN 1/8 IN NPT PRESSU
NEW GITS BROS 18013 SIGHT 1/4 IN NPT GAUGE D399756
DWYER 2001 MAGNEHELIC 0-1.0IN-H2O 4 IN 1/8 IN NPT PRESS
PNEUMATECH 2130 DIFFERENTIAL PRESSURE 0-25PSID 3 IN 1/4
NEW MARSH PRESSURE 0-30PSI 2IN FACE 1/4 IN NPT GAUGE D3
ASHCROFT 100C-I THERMOMETER DIAL TEMPERATURE 30-130F 5I
ORANGE RESEARCH 1201PG-1A-2.5L DIFFERENTIAL 0-5PSI PRES
ASHCROFT Q-8451 DURAGAUGE PRESSURE 0-400PSI 4-1/2 IN 1
WEKSLER 141GSDH SUBMARINE THERMOMETER 30-240F TEMPERATU
WIKA 8212228 233.53 2.5 LIQUID 0-30PSI 2-1/2IN 1/4IN NP
WINTERS PFQ907 LIQUID FILLED PRESSURE 0-300PSI 2-1/2IN
USG PRESSURE SOLFRUNT 1-15PSI 4IN 1/2IN GAUGE B201581
SWAGELOK 2000PSI 2-1/2 IN 1/4 IN NPT PRESSURE GAUGE B45
NEW ASHCROFT 45 2462 AS 04B 300 PRESSURE 0-300PSI 1/2IN
ASHCROFT Q-8451 DURAGAUGE PRESSURE 0-600KPA 5 IN 1/2 IN
TRERICE 52-2863 4 14IN SENSOR PROBE TEMPERATURE 25-125F
ASHCROFT TEMPERATURE 50-450C 5 IN DIAL FACE 1/2 IN NPT
ENFM STAINLESS PRECISION PRESSURE 0-15PSI 4 IN 1/4 IN N
TRERICE -5 TO 50C THERMOMETER TEMPERATURE 25-125F 5 IN
ASHCROFT Q-8451 DURAGAUGE PRESSURE 0-160KPA 5 IN 1/2 IN
ASHCROFT Q-8451 DURAGAUGE PRESSURE 0-1600KPA 5 IN 1/2 I
AMSCO STERIS INTERNAL SYPHON PRESSURE 0-100PSI 2-5/8 IN
NEW DWYER 2002 MAGNEHELIC PRESSURE 0-2IN-H2O 4IN FACE 1
ASHCROFT LIQUID FILLED PRESSURE 0-85PSI 4 IN 1 IN GAUGE
TRERICE 52-2863.0 10 IN PROBE TEMPERATURE 25-125F 5 IN
BUDENBERG 12323881 0-30 LB/IN2 1/4 IN NPT PRESSURE GAUG
ASHCROFT DURAGAUGE 2LB SUBD PRESSURE 0-160PSI 6 IN DIAL
NEW DWYER 2215C PRESSURE MAGNEHELIC 0-15PSI 4 IN 1/8 IN
WINTERS PFQ907 LIQUID FILLED PRESSURE 0-300PSI 2-1/2IN
NEW MERCOID DA-21-2-8S PRESSURE SWITCH 10-200PSI 6 IN 1
ASHCROFT Q-8451 DURAGAUGE PRESSURE 0-160KPA 5 IN 1/2 IN
BOURDON 316SS PRESSURE 0-60PSI 0-400KPA 5 IN 1/2 IN NPT
ASHCROFT THERMOMETER 100-800F 3 IN 1/2 IN NPT TEMPERATU
WINTERS TTD405 PRESSURE 0-200PSI TEMPERATURE 30-240F 3I
ASHCROFT Q-8451 DURAGAUGE PRESSURE 0-250KPA 5 IN 1/2 IN
NEW TEL-TRU AA375R 3IN DIAL TEMPERATURE GAUGE STAINLESS
ASHCROFT 316-TUBE/SOCKET 0-600KPA 4 IN 1/2 IN PRESSURE
WIKA 316 SS 0-100PSI 4 IN 1/2 IN NPT PRESSURE GAUGE B40
NEW ASHCROFT 50EI60E040 THERMOMETER BIMETAL 50-300F TEM
ASHCROFT Q-8402 0-300PSI MAX 4-1/2 IN DIAL 1/4 IN NPT
MITUTOYO DT-10 0.5GF JEWELED DIAL TENSION GAUGE D276600
BUDENBERG 12505622 -30 TO 0IN HG NPT PRESSURE 1/4 IN GA
TRERICE 52-2237 10-150C THERMOMETER TEMPERATURE 50-300F
NEW DWYER 2001 MAGNEHELIC 0-1.0IN-H2O 4 IN 1/8 IN NPT G
TRERICE INDUSTRIAL THERMOMETER TEMPERATURE 30-240F 1 IN
LIQUID FILL PRESSURE 0-200PSI 5 IN 3/4 IN NPT GAUGE B30
BOURDON LIQUID FILL 0-200PSI PRESSURE 0-1400KPA 5 IN 1
SWAGELOK 0-60PSI 4 IN 1/4 IN NPT PRESSURE GAUGE B397634
ASHCROFT VACUUM 0-30IN-HG 4-1/2 IN 1/4 IN NPT PRESSURE
NEW ASHCROFT 10177920-1 BIMETAL THERMOMETER 0-250F TEMP
NEW ANDERSON 27-3/4IN PROBE FACE DIGITAL TEMPERATURE GA
MARSH 0-1000PSI 3-1/2 IN 1/4 IN NPT HYDRAULIC PRESSURE
ASHCROFT DURAGAUGE PRESSURE 2500KPA 6IN 1/2IN GAUGE WEL
NEW WEKSLER 5A0444FJX BIMETAL THERMOMETER 0-200F 5 IN 1
DWYER 2002 MAGNEHELIC PRESSURE 0-2IN-H2O 4 IN DIAL FACE
NEW DWYER 2025 MAGNEHELIC DIFFERENTIAL 0-25IN-H2O PRESS
TEL-TRU AA575R THERMOMETER 0-180F 5 IN DIAL 3/4 IN NPT
OIL RITE 6IN SIGHT DUAL THERMOMETER -15-120C LEVEL TEMP
ASHCROFT Q-586 PRESSURE 0-60PSI 5 IN 1/4 IN NPT GAUGE B
ASHCROFT 0-160PSI 1/4 IN NPT PRESSURE GAUGE D468298
POWERS 744-100 REMOTE BULB ACCRITEM TEMPERATURE REGULAT
ASHCROFT 1008SL DURALIFE LIQUID FILLED 0-1500PSI 1/4 IN
WESTON 4200 THERMOMETER 0-150C 2 IN TEMPERATURE GAUGE D
SPAN IPS-220/222 SWITCH INDICATOR PRESSURE 0-300PSI 1/4
PMC DUAL 0-30PSI 0-200KPA 4IN DIAL STAINLESS 1/4 IN NP
ASHCROFT 74-00 DURALIFE WELDED LOWER MOUNT PRESSURE 0-1
NEW WEKSLER BA4C-YPD4-1W PRESSURE 0-30PSI 3-1/2 IN 1/4
ASHCROFT 4300 NPT PRESSURE SWITCH 0-1000PSI 1/4 IN GAUG
UNION CARBIDE 0-4000PSI 2-1/2 IN 1/4 IN NPT PRESSURE GA
NEW APV 37-00 PRESSURE 0-600PSI 4-1/2 IN 7/8 IN GAUGE B
GARDNER DENVER 93F1 REPLACEMENT DISCHARGE THERMOMETER 6
MARSH B467-2 PRESSURE 0-30PSI 0-210KPA 4IN 1/4IN GAUGE
ASHCROFT Q-4832 DURAGAUGE PRESSURE 0-30PSI 5IN DIAL 1/2
NEW VALLEY INSTRUMENT 2240 GXB VAC -1.0-0BAR 2-5/8 IN 1
ASHCROFT 45-1377AS-2L 100 DURAGAUGE 0-100PSI 4-1/2IN DI
NEW NOSHOK 25-200-10-PSI 0-10PSI 2-1/4 IN FACE 1/4 IN N
NEW ASHCROFT DRA5ECA LIQUID NPT PRESSURE -100-300KPA 6
TRERICE PRESSURE 0-100PSI 5 IN DIAL FACE 1/4 IN NPT GAU
TRERICE -40-70C TEMPERATURE -40-160F 5 IN DIAL 1/2 IN N