Server Fault is a question and answer site for system and network administrators. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

I'm in an environment that contains many Supermicro servers equipped with Adaptec and LSI MegaRAID hardware RAID controllers. These controllers contain battery-backed cache modules to help boost write performance and protect data in-transit.

A frequent support issues is RAID controller battery failure. This shifts the array from write-back to write-through mode. There's clearly a negative performance impact as the system runs with degraded write speed. This persists until a downtime window can be established to power the system down and replace the battery.

This is a very routine operation for us; almost weekly across several thousand physical servers... We even have charging stations in place to prep replacement batteries so that can be swapped-in without a charge cycle.

Perhaps I'm spoiled by a long history with HP ProLiant servers and Smart Array RAID controllers, but HP systems typically had battery lifetimes of 4-6 years. They eventually eliminated the use of RAID batteries around 2009. They were replaced with supercapacitor-backed memory modules (flash-backed write cache, or FBWC) and don't require replacement, disposal or a lengthy initial charge cycle.

Since I see the Adaptec and LSI controller battery failures sometimes occurring on systems that have been in service for less than 12 months, I wonder if this is common in other environments.

If this is common, how do other large server environments handle this?

  • Any tips or tricks to handling RAID battery replacements?
  • Are there any configuration parameters that can help?
  • How disruptive is this to operations in your environment?
  • Could poor chassis cooling and temperature be a factor?
  • Are we doing something wrong?
  • Dell PERC controllers are made by LSI. Do Dell environments experience the same short battery lifetimes?

LSI product literature outlining a new-generation battery that can last longer in service than 1 year. enter image description here

HP ProLiant DL585 G2 server with 1000+ day uptime and a happy RAID battery...

# uptime 
 05:38:08 up 1031 days, 44 min, 31 users,  load average: 0.49, 0.64, 0.99

# hpacucli
   Cache Board Present: True
   Cache Status: OK
   Accelerator Ratio: 50% Read / 50% Write
   Total Cache Size: 512 MB
   Battery Pack Count: 1
   Battery Status: OK
share|improve this question
Just a hint: The last generation of Adaptec controllers use supercaps/flash instead of batteries as well. – Sven May 28 '13 at 12:26
Oh, I'm aware that all of the manufacturers have supercap-based solutions now, but given the existing installation footprint, it's hard to make a broad change across the infrastructure. – ewwhite May 28 '13 at 12:28
I have never done this (probably because it sounds like a bad idea and I haven't had the issue as frequently as you are), but you could try replacing a RAID battery on a test server while it is on. Slide it out, take the cover off, disconnect the bad battery, and connect the good, then back in the rack...If all goes well, you have a new battery replacement process that doesn't involve downtime. – August May 28 '13 at 13:49
@August Uhm, as risky procedures go, this sounds pretty high on the "OMG WHERE DID MY DATA GO" list. – Dan May 28 '13 at 13:51
Yep it sure does...I agree it sounds like a horrible idea, but given the situation and requirement for no downtime, it might be worth a shot on a test server (or thirty test servers...) to see if it is possible. What is another option besides redoing the infrastructure to not rely on individual RAID batteries in thousands of servers? – August May 28 '13 at 13:56
up vote 9 down vote accepted

I suspect your Supermicros are broken one way or the other - possibly the battery packs are overheating. Most recent LSIs would report the temperature through MegaCLI - you might want to monitor this value on servers which needed replacement.

root@host:~/SOLARIS# ./MegaCli -AdpBbuCmd -GetBbuStatus -aALL

BBU status for Adapter: 0

BatteryType: BBU
Temperature: 41 C

I have seen a couple of Dell and Fujitsu systems with LSI BBU controllers, none of them had yearly battery pack replacement (except you screwed the pack up by deep-discharge). The typical life time has been around 3 to 5 years.

share|improve this answer
I would add that unless the system EXPLICITLY authorizes hot replacement of the RAID BBU I would not attempt it. I've never seen a system require annual replacement of the RAID cache battery. 3-5 years is a typical service life. – voretaq7 May 28 '13 at 21:49
I think you got it! – ewwhite May 29 '13 at 19:34

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.