On 10/21/2013 06:47 PM, Piergiorgio Sartor wrote:
Interesting, then logic would suggest to (b)cache
the components of the RAID.
Of, even better, to (b)cache /dev/sd[ab] (in this
case) and cover, in this way, everything.
Well, I agree, there's more to it. Like cost. One could consider to pair
serveral HHD' each with a dedicated bcache SSD. And from that one could
build a RAID array. This RAID array has excellent (read) performance
because of the combined SSD performance. This storage system does break
when one of the HDD's or SDD's breaks, which is also a nice feature. So
if it weren't for the cost (and the number of availbale SATA connectors)
this could be interresting. But it's all a matter of requirements of course.
It's a desktop PC, I notice that performances
mainly depend on the storage subystem, the rest
(CPU, memory, GPU) is fine for me.
In my desktop PC I'm running singls SSD bcache on a RAID5 array. The
performance is fine, and when the SSD breaks, well, I hope the FS on the
HDD can be recovered. And if not? Well, it's only a desktop PC.
And when using multiple SSD's for reduncancy, the following article
covers some interresting features in bcache:
http://www.linux.com/news/featured-blogs/200-libby-clark/728209-about-the-linux-kernel-bcache
Quote "Multiple SSDs will allow us to mirror dirty data and metadata,
but not clean data - you get redundancy without wasting SSD space
duplicating clean cached data".
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