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I have a proliant server which requires a cache battery replacement.

Can you please advise what are the implications if this is not replaced over time. many thanks

Upen desai
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The battery will degrade over time, eventually getting marked as "failed" by the controller. At this point, it can no longer guarantee that cached writes will be stored correctly on dish, so it will turn off its cache layer, significantly decreasing performance.

EEAA
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    Thank you for reply so quickly. This is our backup server and is getting replaced. But we may use it some time in the future in case we have to do any restores. So Wanted to find out if its ok not to replace the battery. Many thanks – Upen desai Apr 04 '13 at 13:03
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The life of a controller battery on HP Smart Arrays is ~3 years.

The purpose of the array battery is to provide power protection for the controller's write cache. The is a data protection mechanism that allows writes to the cache to be acknowledged by a lower-latency cache versus waiting on the underlying disks.

Typically, failure of this battery disables the cache, impacting write speed of the system.

For the past few years, firmware revisions for these controllers enabled a "cache override" function which allows you to ignore the battery's failed state and keep the cache enabled. There is a data safety risk (e.g. If you lose power suddenly), but sometimes avoiding the performance degradation is worth it.

In short, you can ignore the battery failure for as long as you wish. Write performance will suffer unless you enable the cache battery override feature.

Modern controllers use non-volatile flash with a supercapacitor to avoid the need to replace batteries.

ewwhite
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The battery elements used in P800 BBWC module are 1.2V 500mAh NiMH x4 - I have replaced many of those with regular AA NiMH batteries (of higher capacity) using a battery holder like this enter image description here

Alex P.
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  • This is good advice, but does not actually answer the question. It would probably work better as a comment with a text link to the image. – Andrew B Apr 04 '13 at 13:52
  • That's crazy :) Does it work? Why didn't you use the HP part? – ewwhite Apr 04 '13 at 14:05
  • It does work - why wouldn't it? I am suggesting to replace just the battery elements leaving the battery controller in place. I did not use the HP part because I did not have time to wait for the delivery - so I just used whatever spare parts I had. – Alex P. Apr 04 '13 at 15:36