最近集羣機器總是莫名其妙的Down機，出問題的時候機器不響應，遠程管理卡也連接不上，只能聯繫IDC硬重啓，後來找到廠商說要在BIOS關閉c-stats，問題不知道是否解決，先了解下c-stats是幹什麼的：
在Intel的一個網頁上看到：
CPU C-states arecore power states requested by the Operating System Directed Power Management(OSPM) infrastructure that define the degree to which the processor is"sleeping". C0 indicates a normal operation. All other C-states(C1-Cn) describe states where the processor clock is inactive (cannot executeinstructions) and different parts of the processor are powered down. DeeperC-states have longer exit latencies (the time to transition back to C0) butsave more power. The processor can override an OSPM request and automaticallydemote a specific C-state request. For example, the OSPM may request C6 but theprocessor may actually use C3.
主要的級別如下：
C0– Active: CPU is on. C0 is the operating state.
C1– Auto Halt: core clock is off. C1 is a state where the processor is notexecuting instructions, but can return to an executing state essentiallyinstantaneously. Some processors also support an Enhanced C1 state (C1E) forlower power consumption.
C2– Stop Clock: core and bus clocks are off. C2 is a state where the processormaintains all software-visible state, but may take longer to wake up.
C3– Deep Sleep: clock generator is off. C3 is a state where the processor doesnot need to keep its cache coherent, but maintains other states. Someprocessors have variations on the C3 state (Deep Sleep, Deeper Sleep, etc.)that differ in how long it takes to wake the processor.
C4– Deeper Sleep: reduced VCC
DC4– Deeper C4 Sleep: further reduced VCC
總而言之是用來在非CPU-bound型server上節能用的，在一定條件下進入休眠狀態；
搜了一下確實是有這方面的Bug：
http://en.community.dell.com/support-forums/servers/f/956/t/19433716.aspx
另外，和節能相關的在CentOS6.2上還有個Bug，power_saving導致高負載：
https://lkml.org/lkml/2012/6/13/458
http://en.community.dell.com/support-forums/servers/f/1466/p/19456558/20387384.aspx
想起來前天看到的一篇因爲內存問題導致bit變化進而導致db crash的問題，真是到處都有坑啊