mSATA SSD over USB adater: 300MB/s @ Linux versus 100MB/s @ FreeBSD

Gary Jennejohn gljennjohn at gmail.com
Thu Nov 5 15:44:22 UTC 2020


On Thu, 5 Nov 2020 15:26:35 +0100
Hans Petter Selasky <hps at selasky.org> wrote:

> On 2020-11-05 14:05, vermaden wrote:
> > So we should slow down Linux so FreeBSD can keep up?:)  
> 
> Please also keep in mind that Linux has a data cache on /dev/sdb,
> while FreeBSD always goes to the device!
> 
> Try to disable caching in Linux first.
> 

This is true.  Linux will happily cache megabytes of data, which makes the whole
transfer seem to be faster.  I've observed this behavior in Linux myself.  dd
claims to be finished but then it can take minutes before the data actually
land on the target disk.  This is easily seen with e.g. gkrellm2.

-- 
Gary Jennejohn


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