p410 cache

[devboy_1]

Hi,

Using DL360 G7 which has a P410 RAID controller. I didn't purchase nor install it.

The array configuration utility has the following to say about the cache battery:

Cache Backup Power Source Capacitor
Battery/Capacitor Pack Count 1
Battery/Capacitor Status OK

My question is what is the difference between a battery and a capacitor in this respect? I've been looking all over here: http://h18004.www1.hp.com/products/servers/proliantstorage/arraycontrollers/index.html
Can't find anything that's called a capacitor.

Can someone please explain the difference between a battery pack and a capacitor pack?


Cheers,
DB

[SMR]

Batteries take up to 72 hours to charge, and hold a charge for an average of 48 hours, they have been used on write cache backup (BBWC) for quite some time.

Flash backed write cache is the new stuff, uses capacitors that recharge in a matter of minutes and hold data for a lot longer.

If you have Flash backed write cache (FBWC) you have a capacitor instead of a battery.

[devboy_1]

Hi SMR,

OK, so 2 questions:
1. Where in the "more information" or diagnostics report does it specify which cache type is installed? Is is something built into the P410i controller or some extension device (as far as I know the "batteries" themselves are optional)?

2. Our of curiosity, FBCW means that all data is cached on the flash component or it works with RAM that get's flushed to the flash on power loss?

[Daniel Bowers]

RE: #2
The flash device is only used on a power-loss event. DRAM is still used for the cache during normal operations; when power is lost, everything in the cache's DRAM is copied to flash.

The capacitor just provides the power needed to complete the copy.