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FFS and write cache


Using standard 7200 RPM SATA disks, I see around 50MB/s sequential write 
performance with write cache enabled, and around 3MB/s with the cache disabled. 
(Tested with 'dd'.)

I understand this isn't NetBSD's fault, but it's somewhat unfortunate, since it 
means that for many workloads, the only way to get acceptable performance is to 
use an nvram write cache, or turn on the disk write cache and risk disk 
corruption on power failure.

Has there been any progress on using disk features like explicit cache flush, 
or NCQ, to improve performance on such disks without the risk that enabling the 
write cache entails?

(I'm currently using FreeBSD with ZFS on one system, mostly because of this 
performance issue, but I'd like to switch it to NetBSD.)


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