啥是BBU
BBU到底是个啥？
因为我们不是搞硬件的，我们可以粗略地把BBU当成一块电池，这块电池用来保护RAID卡上的Cache。一般来讲，RAID卡都会有1G的Cache，这一层Cache对于RAID的写入至关重要，使用RAID卡的Cache可以显著地提升RAID的写入性能。
HW Configuration
================
SAS Address : 500605b009e97840
BBU : Present
Alarm : Present
NVRAM : Present
Serial Debugger : Present
Memory : Present
Flash : Present
Memory Size : 1024MB <--------1024MB 即RAID Cache的大小
但是这里面有个问题，就是掉电保护。我们都知道文件系统fsync或者sync相关的系统调用，会将页高速缓存（Page Cache）中的dirty flush到底层块设备，对于RAID管理的块设备，如果使用了RAID Cache，那么sync也只保证写入RAID Cache，并不保证一定落在底层持久化的磁盘上。这就带来了致命的风险，即异常掉电的时候，RAID Cache中的数据可能会丢失。
这里面有一个dirty冲刷周期的参数：
Cache Flush Interval : 4s
因此，掉电的时候，可能会有过去4秒的dirty内容还未刷入持久化的设备，
那怎么办？BBU就粉墨登场了。
注意，如果你的RAID卡没有BBU，却非要使用WriteBack 的Write Policy，那么掉电之后，丢数据几乎是肯定的。所以要享受RAID 卡上Cache带来的性能提升，就必须配置BBU。
掉电之后，BBU能保护RAID Cache中的数据多久
BBU是能保护RAID Cache中尚未来得及写入底层持久化设备的数据，但是BBU不是核反应堆，它的保护能力是有限度的。一般来讲BBU可以保护RAID Cache中的数据2天左右。
Design Mode : 48+ Hrs retention with a non-transparent learn cycle and moderate service life.
上述内容的含义是说，BBU承诺48小时的保护。
我们曾经有过案例，关机是强制关机，开机之后发现有data loss，后来才知道，强制关机7天之后，才开机，BBU守护了RAID Cache中dirty 内容一段时间之后，终于油尽灯枯。
如果设置Write Policy为NO Write Cache if Bad BBU，即BBU剩余电量不足与保护Cache中的内容1天以上，那么会自动讲Write Policy从WB调整成WT。
注意，机器上电之后，RAID cache中的数据会写入底层的磁盘。
如何检查是否存在BBU
MegaCli AdpAllInfo －A0中会在HW Configuration部分显示是否存在BBU：
HW Configuration
================
SAS Address : 500605b009e97840
BBU : Present <-------------- present表示存在BBU
Alarm : Present
NVRAM : Present
Serial Debugger : Present
Memory : Present
Flash : Present
Memory Size : 1024MB
RAID的WritePolicy 何时会变成WT
我们都知道WB的效能比WT的效能要高，有以下情况会变成WT
用户设置WritePolicy 为WT
MegaCli LDSetProp WT -L2 -A0
设置了Write Policy 为WB并且设置了NoCachedBadBBU，但是电池坏了或者有故障了battery处在“low-charge state”阶段
简单来说，就是说电池的电量不足以保持24小时的数据时，就会讲策略从WB改成WT
seqNum: 0x00016bef
Time: Fri Apr 28 05:08:02 2017
Code: 0x000000c3
Class: 1
Locale: 0x08
Event Description: BBU disabled; changing WB virtual disks to WT, Forced WB VDs are not affected
Event Data:
===========
None
这种行为一般发生在Learn Cycle的 Discharging Cycle步骤，因为会主动放点，会导致电池处于low－charge state。在这个情况下，我们通过MegaCli命令是无法将Write Policy改成WB的：
root@EBS-005-PUB01-JD-Xian:/var/log# /opt/MegaRAID/MegaCli/MegaCli64 -LDSetProp WB -immediate -L2 -A0
Battery capacity is below the threshold value
Adapter 0: Set Property Failed on Vd object
Exit Code: 0x01
注意，并不是说电池电量满足可以保证24小时数据时就会恢复成WB，而是更迟一些，电池电量充满到85%之后，才会从WT改成WB。
seqNum: 0x00016bf6
Time: Fri Apr 28 05:09:04 2017
Code: 0x00000093
Class: 0
Locale: 0x08
Event Description: Battery started charging
Event Data:
===========
None
seqNum: 0x00016bf7
Time: Fri Apr 28 06:59:34 2017
Code: 0x000000c2
Class: 0
Locale: 0x08
Event Description: BBU enabled; changing WT virtual disks to WB
Event Data:
===========
None
理解BBU的的Capacity信息
root@node01:~# /opt/MegaRAID/MegaCli/MegaCli64 -AdpBbuCmd -A0
BBU status for Adapter: 0
BatteryType: iBBU-09
Voltage: 3986 mV
Current: 0 mA
Temperature: 35 C
Battery State: Optimal
Design Mode : 48+ Hrs retention with a non-transparent learn cycle and moderate service life.
BBU Firmware Status:
Charging Status : None
Voltage : OK
Temperature : OK
Learn Cycle Requested : Yes
Learn Cycle Active : No
Learn Cycle Status : OK
Learn Cycle Timeout : No
I2c Errors Detected : No
Battery Pack Missing : No
Battery Replacement required : No
Remaining Capacity Low : No
Periodic Learn Required : No
Transparent Learn : No
No space to cache offload : No
Pack is about to fail & should be replaced : No
Cache Offload premium feature required : No
Module microcode update required : No
BBU GasGauge Status: 0x0180
Relative State of Charge: 89 %
Charger System State: 1
Charger System Ctrl: 0
Charging current: 0 mA
Absolute state of charge: 70 %
Max Error: 0 %
Battery backup charge time : 48 hours +
BBU Capacity Info for Adapter: 0
Relative State of Charge: 89 %
Absolute State of charge: 70 %
Remaining Capacity: 1055 mAh
Full Charge Capacity: 1198 mAh
Run time to empty: Battery is not being charged.
Average time to empty: 2 Hour, 7 Min.
Estimated Time to full recharge: Battery is not being charged.
Cycle Count: 12
BBU Design Info for Adapter: 0
Date of Manufacture: 03/19, 2012
Design Capacity: 1500 mAh
Design Voltage: 4100 mV
Specification Info: 0
Serial Number: 562
Pack Stat Configuration: 0x0000
Manufacture Name: LS36691
Firmware Version :
Device Name: iBBU-09
Device Chemistry: LION
Battery FRU: N/A
Transparent Learn = 0
App Data = 0
BBU Properties for Adapter: 0
Auto Learn Period: 28 Days
Next Learn time: Thu Jun 1 14:17:44 2017
Learn Delay Interval:0 Hours
Auto-Learn Mode: Enabled
BBU Mode = 5
Exit Code: 0x00
首先要关注的信息是：
BatteryType: iBBU-09
这个显示的是BBU的型号信息。
BBU由锂离子电池和电子控制电路组成。 锂离子电池的寿命取决于其老化程度，从出厂之后，无论它是否被充电及它的充放电次数多与少，锂离子电池的容量将慢慢的减少。这意味着一个老电池无法像新电池那么持久。 也就决定了BBU的相对充电状态(Relative State of Charge)不会等于绝对充电状态(Absolute State of Charge)。
这个方面并不难理解，就想笔记本的电池一样，新买来的笔记本电池充满电之后，能够支撑笔记本使用5小时，但是随着时间流逝，使用很久之后，笔记本电池充饱电，也不能支撑笔记本使用5小时，可能只能支撑3小时，这是由于电池老化引起的。BBU也是同样的道理：
Relative State of Charge: 89 %
Absolute State of charge: 70 %
Remaining Capacity: 1055 mAh
Full Charge Capacity: 1198 mAh
BBU Design Info for Adapter: 0
Design Capacity: 1500 mAh
这一段的含义是说，刚出厂的BBU，设计容量是1500 mAh，但是随着长时间的使用，电池开始老化，目前充饱电，最多只能充到1198 mAh， 另外当前的电量是1055 mAh。
Relative State of Charge ＝ 1055 ／ 1198 ～ 89%
Absolute State of charge ＝ 1055 ／ 1500 ～ 70%
另外一个和BBU Capacity相关的参数为：
Remaining Capacity Low : No
注意，一般来讲，BBU要保持住能够保护RAID Cache48小时的电量，如果保持不了，那么这个值会是Yes。 对于BBU 07这个值一般是600mAh，而BBU 08，这个值需要是674 mAh，BBU 09我暂时没有查到。
一般来讲，这个参数可以用来确定BBU是否需要替换。正常情况下，Remain Capacity Low应该是No，始终是No，因为会BBU会及时充放电，所以这个值不应该是Yes，如果这个值为Yes，这说明BBU需要更换了。
这种情况下会有以下现象发生：
一般来讲，会从eventlog中发现这样的输出：
Current capacity of the battery is below threshold
如果Write Policy为WB，并且 No Write Cache if Bad BBU，那么BBU的状态被强制改成WT无法将WT改成WB，会报如下错误：
root@EBS-005-PUB01-JD-Xian:/var/log# /opt/MegaRAID/MegaCli/MegaCli64 -LDSetProp WB -immediate -L2 -A0
Battery capacity is below the threshold value
Adapter 0: Set Property Failed on Vd object
Exit Code: 0x01
我们在现场，确实曾经发现有BBU出现问题
root@EBS-005-PUB01-JD-Xian:/var/log# /opt/MegaRAID/MegaCli/MegaCli64 -AdpBBUCMD -Aall
BBU status for Adapter: 0
BatteryType: iBBU-09
Voltage: 3893 mV
Current: 536 mA
Temperature: 46 C
Battery State: Degraded(Need Attention)
A manual learn is required.
Design Mode : 48+ Hrs retention with a non-transparent learn cycle and moderate service life.
BBU Firmware Status:
Charging Status : Charging
Voltage : OK
Temperature : OK
Learn Cycle Requested : Yes
Learn Cycle Active : No
Learn Cycle Status : OK
Learn Cycle Timeout : No
I2c Errors Detected : No
Battery Pack Missing : No
Battery Replacement required : No
Remaining Capacity x : Yes
Periodic Learn Required : No
Transparent Learn : No
No space to cache offload : No
Pack is about to fail & should be replaced : No
Cache Offload premium feature required : No
Module microcode update required : No
BBU GasGauge Status: 0x0100
Relative State of Charge: 34 %
Charger System State: 1
Charger System Ctrl: 0
Charging current: 536 mA
Absolute state of charge: 29 %
Max Error: 0 %
Battery backup charge time : 19 hours
BBU Capacity Info for Adapter: 0
Relative State of Charge: 35 %
Absolute State of charge: 30 %
Remaining Capacity: 452 mAh
Full Charge Capacity: 1320 mAh
Run time to empty: Battery is not being charged.
Average time to empty: 54 Min.
Estimated Time to full recharge: 2 Hour, 32 Min.
Cycle Count: 0
BBU Design Info for Adapter: 0
Date of Manufacture: 07/08, 2015
Design Capacity: 1500 mAh
Design Voltage: 4100 mV
Specification Info: 0
Serial Number: 475
Pack Stat Configuration: 0x0000
Manufacture Name: LS36691
Firmware Version :
Device Name: iBBU-09
Device Chemistry: LION
Battery FRU: N/A
Transparent Learn = 0
App Data = 0
BBU Properties for Adapter: 0
Auto Learn Period: 28 Days
Next Learn time: Wed May 3 10:49:00 2017
Learn Delay Interval:0 Hours
Auto-Learn Mode: Enabled
BBU Mode = 5
Exit Code: 0x00
root@EBS-005-PUB01-JD-Xian:/var/log# /opt/MegaRAID/MegaCli/MegaCli64 -AdpBBUCMD GetBbuCapacityInfo -A0
BBU Capacity Info for Adapter: 0
Relative State of Charge: 37 %
Absolute State of charge: 32 %
Remaining Capacity: 485 mAh
Full Charge Capacity: 1320 mAh
Run time to empty: Battery is not being charged.
Average time to empty: 58 Min.
Estimated Time to full recharge: 2 Hour, 28 Min.
Cycle Count: 0
Exit Code: 0x00
注意上图，BBU 的Remain Capacity为 452 mAh，而出厂标称值为1500 mAh， Absolute State of charge: 30 %，这时候，其实已经出现问题了，注意如下输出：
Battery State: Degraded(Need Attention)
A manual learn is required.
检查BBU的健康情况
如何检查BBU是否需要更换呢？
RAID batteries - time to replace?这篇文章给出了一个思路：
root@EBS-005-PUB01-JD-Xian:/var/log# /opt/MegaRAID/MegaCli/MegaCli64 -AdpBBUCMD GetBbuCapacityInfo -A0
BBU Capacity Info for Adapter: 0
Relative State of Charge: 37 %
Absolute State of charge: 32 % ---->查看Absolute State of charge的值
Remaining Capacity: 485 mAh
Full Charge Capacity: 1320 mAh
Run time to empty: Battery is not being charged.
Average time to empty: 58 Min.
Estimated Time to full recharge: 2 Hour, 28 Min.
Cycle Count: 0
Exit Code: 0x00
文章给出了如下shell脚本
bbugood() { [ $(megacli adpbbucmd GetBbuCapacityInfo ${1:-a0} | sed -ne '/^[aA]bsolute/{s/^[^[:digit:]]*\([[:digit:]]\+\).*$/\1/p}') -gt 54 ] ;}
这个shell语句有些问题，因为很明显Absolute并不出现在行首，行首还有额外的空格，因此可以使用如下方法获取Absolute State of charge的值：
/opt/MegaRAID/MegaCli/MegaCli64 adpbbucmd GetBbuCapacityInfo -a0 | sed -ne '/[aA]bsolute/{s/^[^[:digit:]]*\([[:digit:]]\+\).*$/\1/p}'
70
作者给出了经验数值，54%，低于54%则判定BBU not good。
注意，Learn Cycle的时候会先放电，然后充电，这个过程中可能会低于经验值，但是要进一步分析Battery State和Learn Cycle Status来判断是否BBU已经老化。
另外一个有价值的参数是：
Battery Replacement required : No
当这个值为Yes的时候当然需要更换电池，但是这个参数一般比较滞后，很难通过它预判BBU需要更换。
BBU的Auto Relearn
为了记录电池的放电曲线，以便控制器了解电池的状态，例如最大和最小电压等，同时为了延长电池的寿命，默认会启用自动校准模式(AutoLearn Mode).
我们首先通过EventLog对 Auto Learn全过程做一个直观了解：
(注意BBU的时间和shell命令输出的时间比较，相差8个小时，不要被时间迷惑)
预告阶段，在relearn start之前4天，2天，1天，5小时，分别预告，要开始relearn了
seqNum: 0x00012827
Time: Mon Apr 24 20:49:28 2017
Code: 0x0000009d
Class: 0
Locale: 0x08
Event Description: Battery relearn will start in 4 days
Event Data:
===========
None
seqNum: 0x00012828
Time: Wed Apr 26 20:48:58 2017
Code: 0x0000009e
Class: 0
Locale: 0x08
Event Description: Battery relearn will start in 2 day
Event Data:
===========
None
seqNum: 0x00012829
Time: Thu Apr 27 20:48:43 2017
Code: 0x0000009f
Class: 0
Locale: 0x08
Event Description: Battery relearn will start in 1 day
Event Data:
===========
None
seqNum: 0x0001282a
Time: Fri Apr 28 15:49:28 2017
Code: 0x000000a0
Class: 0
Locale: 0x08
Event Description: Battery relearn will start in 5 hours
Event Data:
===========
None
第一阶段：控制器把BBU电池充满电(该步骤可能是放电后充电或直接充电，如果电池刚好满电，则直接进入第二阶段)
seqNum: 0x0001282b
Time: Fri Apr 28 20:50:38 2017
Code: 0x0000009b
Class: 0
Locale: 0x08
Event Description: Battery relearn pending: Battery is under charge
Event Data:
===========
None
第一阶段的典型时间是1分钟左右。
第二阶段 开始校准, 对BBU电池执行放电。 注意，随着放电的进行，当电量低到一定程度的时候，会讲Write Policy从WB改成WT（Force WB的除外）。
注意，当relearn开始的时候，Learn Cycle Active开始从No变成Yes。
这个阶段进一步细分，其实可以细化成两个阶段
当放电量较少，剩余电量仍然超过安全门限，2A阶段:
Battery State: Optimal
随着时间流逝，放电量越来也多，剩余的电量越来越少，当剩余电量低于安全门限的时候，会将WT改成WB，此时
Battery State: Learning
我看了我的一台机器，当剩余电量为 888 mAh的时候，尚为2A阶段，当剩余电量为883 mAh的时候，已经为2B阶段了。
整个第二阶段，相关的event log如下：
seqNum: 0x0001282c
Time: Fri Apr 28 20:51:43 2017
Code: 0x00000097
Class: 0
Locale: 0x08
Event Description: Battery relearn started
Event Data:
===========
None
seqNum: 0x0001282d
Time: Fri Apr 28 20:52:48 2017
Code: 0x00000094
Class: 0
Locale: 0x08
Event Description: Battery is discharging
Event Data:
===========
None
seqNum: 0x0001282e
Time: Fri Apr 28 20:52:48 2017
Code: 0x00000098
Class: 0
Locale: 0x08
Event Description: Battery relearn in progress
Event Data:
===========
None
seqNum: 0x0001282f
Time: Fri Apr 28 21:17:45 2017
Code: 0x000000c3
Class: 1
Locale: 0x08
Event Description: BBU disabled; changing WB virtual disks to WT, Forced WB VDs are not affected
Event Data:
===========
None
从开始校准到校准结束，这个时间的典型值是1个半小时。
放电完成后，完成校准，并重新开始充电， 直接达到最大电量， 整个Learn Cycle才算完成 注意: 如果第二或第三阶段被中断，重新校准的任务会停止，而不会重新执行
seqNum: 0x00012835
Time: Fri Apr 28 22:22:43 2017
Code: 0x00000099
Class: 0
Locale: 0x08
Event Description: Battery relearn completed
Event Data:
===========
None
seqNum: 0x00012836
Time: Fri Apr 28 22:23:48 2017
Code: 0x00000093
Class: 0
Locale: 0x08
Event Description: Battery started charging
Event Data:
===========
None
seqNum: 0x00012837
Time: Fri Apr 28 22:42:13 2017
Code: 0x000000c2
Class: 0
Locale: 0x08
Event Description: BBU enabled; changing WT virtual disks to WB
Event Data:
===========
None
seqNum: 0x0001283b
Time: Fri Apr 28 23:11:28 2017
Code: 0x000000f2
Class: 0
Locale: 0x08
Event Description: Battery charge complete
Event Data:
===========
None
一般充电20分钟之后，就可以讲Write Policy从WT改成WB。充电过程会继续，知道充电完成，一般充电过程过程会在1小时之内。
其实我们更关心的是，从WB改成WT，到WT改回WB，这段时间是多久，因为这段时间内，写入性能会显著下降，典型值是一个半小时左右。
seqNum: 0x0000fac8
Time: Fri Feb 3 21:18:10 2017
Code: 0x000000c3
Class: 1
Locale: 0x08
Event Description: BBU disabled; changing WB virtual disks to WT, Forced WB VDs are not affected
Event Data:
===========
None
seqNum: 0x0000fad0
Time: Fri Feb 3 22:44:48 2017
Code: 0x000000c2
Class: 0
Locale: 0x08
Event Description: BBU enabled; changing WT virtual disks to WB
Event Data:
===========
None
一般来讲，为了延长寿命，都会打开AutoLearn的模式，如果不打开，会降低BBU的寿命。
root@EBS-005-PUB01-JD-Xian:/var/log# /opt/MegaRAID/MegaCli/MegaCli64 -AdpBBUCMD GetBbuProperties -A0
BBU Properties for Adapter: 0
Auto Learn Period: 28 Days
Next Learn time: Wed May 3 10:49:00 2017
Learn Delay Interval:0 Hours
Auto-Learn Mode: Enabled
BBU Mode = 5
Exit Code: 0x00
另一个需要关心的问题是，多久之行一次Auto Learn，这取决于硬件，比如我们这个是28天一次。
手动发起Relearn
注意，我们可以通过如下命令，手动发起Relearn
/opt/MegaRAID/MegaCli/MegaCli64 -AdpBbuCmd -BbuLearn -aALL
这个命令一旦执行，以下事情就会发生：
Remaining Capacity会不断升高，慢慢逼近Full Charge Capacity。
可以通过如下指令观察：
/opt/MegaRAID/MegaCli/MegaCli64 -AdpBbuCmd -GetBbuCapacityInfo -A0
输出如下：
Every 2.0s: /opt/MegaRAID/MegaCli/MegaCli64 -AdpBBUCMd -GetBBUCapacityInfo -A0 Mon May 29 19:26:58 2017
BBU Capacity Info for Adapter: 0
Relative State of Charge: 95 %
Absolute State of charge: 75 %
Remaining Capacity: 1127 mAh
Full Charge Capacity: 1198 mAh
Run time to empty: Battery is not being charged.
Average time to empty: 2 Hour, 15 Min.
Estimated Time to full recharge: 26 Min.
Cycle Count: 12
Exit Code: 0x00
Every 2.0s: /opt/MegaRAID/MegaCli/MegaCli64 -AdpBBUCMd -GetBBUCapacityInfo -A0 Mon May 29 19:38:59 2017
BBU Capacity Info for Adapter: 0
Relative State of Charge: 98 %
Absolute State of charge: 78 %
Remaining Capacity: 1171 mAh
Full Charge Capacity: 1198 mAh
Run time to empty: Battery is not being charged.
Average time to empty: 2 Hour, 21 Min.
Estimated Time to full recharge: 13 Min.
Cycle Count: 12
Exit Code: 0x00
等待稍许时间，Charging Status会变成 Charging
BBU status for Adapter: 0
BatteryType: iBBU-09
Voltage: 4091 mV
Current: 169 mA
Temperature: 38 C
Battery State: Optimal
Design Mode : 48+ Hrs retention with a non-transparent learn cycle and moderate service life.
BBU Firmware Status:
Charging Status : Charging <----------变成charging状态
Voltage : OK
Temperature : OK
Learn Cycle Requested : Yes
Learn Cycle Active : No
Learn Cycle Status : OK
Learn Cycle Timeout : No
I2c Errors Detected : No
Battery Pack Missing : No
Battery Replacement required : No
Remaining Capacity Low : No
Periodic Learn Required : No
Transparent Learn : No
No space to cache offload : No
Pack is about to fail & should be replaced : No
Cache Offload premium feature required : No
Module microcode update required : No
当充电完成，Charging Statue变成None。
＃ 11:46:00 完成充电
seqNum: 0x0000a640
Time: Mon May 29 11:46:00 2017
Code: 0x000000f2
Class: 0
Locale: 0x08
Event Description: Battery charge complete
Event Data:
===========
None
Every 2.0s: /opt/MegaRAID/MegaCli/MegaCli64 -AdpBBUCMd -GetBBUCapacityInfo -A0 Mon May 29 19:46:31 2017
BBU Capacity Info for Adapter: 0
Relative State of Charge: 100 %
Absolute State of charge: 79 %
Remaining Capacity: 1188 mAh
Full Charge Capacity: 1198 mAh
Run time to empty: Battery is not being charged.
Average time to empty: 2 Hour, 23 Min.
Estimated Time to full recharge: Battery is not being charged.
Cycle Count: 12
Exit Code: 0x00
Every 2.0s: /opt/MegaRAID/MegaCli/MegaCli64 -AdpBBUCmd -A0 Mon May 29 19:46:50 2017
BBU status for Adapter: 0
BatteryType: iBBU-09
Voltage: 4067 mV
Current: 0 mA
Temperature: 38 C
Battery State: Optimal
Design Mode : 48+ Hrs retention with a non-transparent learn cycle and moderate service life.
BBU Firmware Status:
Charging Status : None
Voltage : OK
Temperature : OK
Learn Cycle Requested : Yes
Learn Cycle Active : No
Learn Cycle Status : OK
Learn Cycle Timeout : No
I2c Errors Detected : No
Battery Pack Missing : No
Battery Replacement required : No
Remaining Capacity Low : No
Periodic Learn Required : No
Transparent Learn : No
No space to cache offload : No
Pack is about to fail & should be replaced : No
Cache Offload premium feature required : No
Module microcode update required : No
BBU GasGauge Status: 0x0200
过一段时间，Relearn 开始，开始放电，此时 Learn Cycle Active 变成Yes，Charging Status变成 Discharging
seqNum: 0x0000a641
Time: Mon May 29 12:18:30 2017
Code: 0x00000097
Class: 0
Locale: 0x08
Event Description: Battery relearn started
Event Data:
===========
None
BBU status for Adapter: 0
BatteryType: iBBU-09
Voltage: 3989 mV
Current: -313 mA
Temperature: 37 C
Battery State: Optimal
Design Mode : 48+ Hrs retention with a non-transparent learn cycle and moderate service life.
BBU Firmware Status:
Charging Status : Discharging <------------relearn的开始是discharging
Voltage : OK
Temperature : OK
Learn Cycle Requested : Yes
Learn Cycle Active : Yes <-----------relearn start ，此处从No变成Yes
Learn Cycle Status : OK
Learn Cycle Timeout : No
I2c Errors Detected : No
Battery Pack Missing : No
Battery Replacement required : No
Remaining Capacity Low : No
Periodic Learn Required : No
Transparent Learn : No
No space to cache offload : No
Pack is about to fail & should be replaced : No
Cache Offload premium feature required : No
Module microcode update required : No
在这个Discharing过程中，电量逐渐降低：
Every 2.0s: /opt/MegaRAID/MegaCli/MegaCli64 -AdpBBUCMd -GetBBUCapacityInfo -A0 Mon May 29 20:38:16 2017
BBU Capacity Info for Adapter: 0
Relative State of Charge: 91 %
Absolute State of charge: 72 %
Remaining Capacity: 1088 mAh <---------电量在逐渐减少
Full Charge Capacity: 1198 mAh
Run time to empty: 3 Hour, 32 Min.
Average time to empty: 2 Hour, 11 Min.
Estimated Time to full recharge: Battery is not being charged.
Cycle Count: 12
Exit Code: 0x00
当电量低到一定程度时，就会将Write Policy 从WB改成WT，Remaining Capacity Low 从No变成Yes
seqNum: 0x0000a671
Time: Mon May 29 14:10:22 2017
Code: 0x000000c3
Class: 1
Locale: 0x08
Event Description: BBU disabled; changing WB virtual disks to WT, Forced WB VDs are not affected
Event Data:
===========
None
Mon May 29 22:10:50 CST 2017
BBU status for Adapter: 0
BatteryType: iBBU-09
Voltage: 3793 mV
Current: -297 mA
Temperature: 40 C
Battery State: Learning
Design Mode : 48+ Hrs retention with a non-transparent learn cycle and moderate service life.
BBU Firmware Status:
Charging Status : Discharging
Voltage : OK
Temperature : OK
Learn Cycle Requested : Yes
Learn Cycle Active : Yes
Learn Cycle Status : OK
Learn Cycle Timeout : No
I2c Errors Detected : No
Battery Pack Missing : No
Battery Replacement required : No
Remaining Capacity Low : Yes <-------电量低到了一定程度，从Remaining Capacity Low 从NO变成Yes
Periodic Learn Required : No
Transparent Learn : No
No space to cache offload : No
BBU Capacity Info for Adapter: 0
Relative State of Charge: 67 %
Absolute State of charge: 58 %
Remaining Capacity: 883 mAh
Full Charge Capacity: 1319 mAh
Run time to empty: 2 Hour, 58 Min.
Average time to empty: 1 Hour, 46 Min.
Estimated Time to full recharge: Battery is not being charged.
Cycle Count: 12
最终BBU的电量会变得非常低，然后校准完成：
seqNum: 0x0000a67a
Time: Mon May 29 17:21:02 2017
Code: 0x00000099
Class: 0
Locale: 0x08
Event Description: Battery relearn completed
Event Data:
===========
None
校准完成以后，Learn Cycle Required和Learn Cycle Active 都变成No,同时，Battery State可能暂时变成Failed状态。
Tue May 30 01:21:15 CST 2017
^M
BBU status for Adapter: 0
BatteryType: iBBU-09
Voltage: 3267 mV
Current: 0 mA
Temperature: 34 C
Battery State: Failed
Design Mode : 48+ Hrs retention with a non-transparent learn cycle and moderate service life.
BBU Firmware Status:
Charging Status : Discharging
Voltage : Low
Temperature : OK
Learn Cycle Requested : No
Learn Cycle Active : No
Learn Cycle Status : OK
Learn Cycle Timeout : No
I2c Errors Detected : No
Battery Pack Missing : No
Battery Replacement required : No
Remaining Capacity Low : Yes
...
BBU Capacity Info for Adapter: 0
Relative State of Charge: 11 %
Absolute State of charge: 9 %
Remaining Capacity: 139 mAh
Full Charge Capacity: 1316 mAh
Run time to empty: Battery is not being charged.
Average time to empty: 17 Min.
Estimated Time to full recharge: 5 Hour, 41 Min.
Cycle Count: 13
注意这个状态不会停留太久。校准完成之后，就开始充电，因此，Battery State变成 Degraded（Charging）,同时Charging Status变成Charging。
Tue May 30 01:22:15 CST 2017
^M
BBU status for Adapter: 0
BatteryType: iBBU-09
Voltage: 3492 mV
Current: 522 mA
Temperature: 34 C
Battery State: Degraded(Charging) <----------状态变成Degraded(Charging)
Design Mode : 48+ Hrs retention with a non-transparent learn cycle and moderate service life.
BBU Firmware Status:
Charging Status : Charging <--------从Discharing变成Charging
Voltage : Low
Temperature : OK
Learn Cycle Requested : No
Learn Cycle Active : No
Learn Cycle Status : OK
Learn Cycle Timeout : No
I2c Errors Detected : No
Battery Pack Missing : No
Battery Replacement required : No
Remaining Capacity Low : Yes
Periodic Learn Required : No
Transparent Learn : No
当充电电量涨到一定程度时，Remaining Capacity Low变成No，Battery Status从Degraded(Charing)变成Optimal，这个时候会将WT改回WB。
seqNum: 0x0000a67c
Time: Mon May 29 18:47:42 2017
Code: 0x000000c2
Class: 0
Locale: 0x08
Event Description: BBU enabled; changing WT virtual disks to WB
Event Data:
===========
None
Exit Code: 0x00
Tue May 30 02:48:26 CST 2017
^M
BBU status for Adapter: 0
BatteryType: iBBU-09
Voltage: 3981 mV
Current: 524 mA
Temperature: 38 C
Battery State: Optimal <-------------Battery State 从Degraded(Charging)变成Optimal
Design Mode : 48+ Hrs retention with a non-transparent learn cycle and moderate service life.
BBU Firmware Status:
Charging Status : Charging
Voltage : OK
Temperature : OK
Learn Cycle Requested : No
Learn Cycle Active : No
Learn Cycle Status : OK
Learn Cycle Timeout : No
I2c Errors Detected : No
Battery Pack Missing : No
Battery Replacement required : No
Remaining Capacity Low : No <-----------Remaining Capacity Low 变成No
Periodic Learn Required : No
Transparent Learn : No
No space to cache offload : No
Pack is about to fail & should be replaced : No
Cache Offload premium feature required : No
Module microcode update required : No
BBU Capacity Info for Adapter: 0
Relative State of Charge: 69 %
Absolute State of charge: 59 %
Remaining Capacity: 897 mAh <----------电量已经足够高了
Full Charge Capacity: 1316 mAh
Run time to empty: Battery is not being charged.
Average time to empty: 1 Hour, 48 Min.
Estimated Time to full recharge: 1 Hour, 36 Min.
Cycle Count: 13
继续充电，知道充电完成，此时Charging Status变成None
seqNum: 0x0000a684
Time: Mon May 29 19:06:07 2017
Code: 0x000000f2
Class: 0
Locale: 0x08
Event Description: Battery charge complete
Event Data:
===========
None
Tue May 30 03:06:28 CST 2017
^M
BBU status for Adapter: 0
BatteryType: iBBU-09
Voltage: 3955 mV
Current: 0 mA
Temperature: 38 C
Battery State: Optimal
Design Mode : 48+ Hrs retention with a non-transparent learn cycle and moderate service life.
BBU Firmware Status:
Charging Status : None ---------------Charging Status从Charging变成None
Voltage : OK
Temperature : OK
Learn Cycle Requested : No
Learn Cycle Active : No
Learn Cycle Status : OK
Learn Cycle Timeout : No
I2c Errors Detected : No
Battery Pack Missing : No
Battery Replacement required : No
Remaining Capacity Low : No
Periodic Learn Required : No
Transparent Learn : No
No space to cache offload : No
Pack is about to fail & should be replaced : No
Cache Offload premium feature required : No
Module microcode update required : No
BBU Capacity Info for Adapter: 0
Relative State of Charge: 80 %
Absolute State of charge: 69 %
Remaining Capacity: 1043 mAh
Full Charge Capacity: 1316 mAh
Run time to empty: Battery is not being charged.
Average time to empty: 2 Hour, 5 Min.
Estimated Time to full recharge: 5 Day, 16 Hour, 30 Min.