On Fri, 10 Aug 2018 12:29:04 -0000 (UTC) mlel...@serpens.de (Michael van Elst) wrote:
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> cryintotheblue...@gmail.com (Sad Clouds) writes: > > >Reading from the virtual RAID drive gives throughput of 892MB/sec for > >raw device, but only 53MB/sec for block device. This is NetBSD-8 > > >Any ideas why block device I/O is so abysmal? Is this something > >specific to NetBSD? > > When using the block device, everything is funneled through the > classic buffer cache. The buffer size is retrieved from the disklabel > and defaults to 2kbyte only. Finally, reads are done synchronously > without significant read-ahead. > > This is specific to NetBSD, but it is hardly used because file I/O > is done by the virtual memory system, bypassing the classic buffer > cache. So there is no incentive to improve the situation as it also > requires a redesign of the buffer cache and some people would rather > get rid of the block device interface. > > So, just don't use it. In particular not for benchmarks :) OK, thanks for the info, I was trying to see what NetBSD I/O would be like on this device if I were to use it for FFS file system, but looks like reading from block device is not the right way to benchmark it. I didn't want to format it with FFS since it has Linux installed, which I use on daily basis.
