Carlos E. R. wrote:
On 27/01/2021 13.04, Per Jessen wrote:
Carlos E. R. wrote:
On 27/01/2021 12.49, Per Jessen wrote:
Carlos E. R. wrote:
On 27/01/2021 10.45, Stakanov wrote:
A question about "battery": is it still an argument if you system is backed up by an UPS? I thought the batteries on controller cards were paramount only on systems that are not protected by a convenient UPS. Wrong?
The idea is, I assume, that battery backed hardware raid detects that the power died and commits everything to disk before finally powering down the HDs.
The battery is there to power the write cache memory until mains power returns. These days it is flash backed cache, not battery backed.
I guess that cache has a significant size?
It depends - in earlier days 64Mb, 128Mb, 256Mb, today 1024Mb. (maybe more).
Let me see. A "Seagate BarraCuda 3.5" 4TB SATA3" has an internal buffer of 256MB. Then those cards don't have a "significant size" of memory, IMHO.
I'm not sure if that is pertinent :-) The built-in cache on the disk drive is for speeding up reads, not writes.
And begs the question about who backs up the hard disk buffer memory.
It is not used for write caching. -- Per Jessen, Zürich (2.2°C) http://www.hostsuisse.com/ - dedicated server rental in Switzerland.