From: Kevin Hui <khui@cs.toronto.edu> To: Alfred Perlstein <bright@mu.org> Cc: freebsd-questions@freebsd.org Subject: Re: Experiencing very slow raw write speeds on /dev/ad1 Message-ID: <Pine.GSO.4.21.0108101106250.9706-100000@gardiner.cs> In-Reply-To: <20010810025156.N85642@elvis.mu.org>
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> > Adding write caching helped a lot. Now the write speed jumps to ~15.8MB/s
> > instead of the previous 3.5MB/s.
> > Are there any other such settings I should pay attention to? I asked
> > because I believe that the performance is still not as good as can be. I
> > have the rawio program running under Linux with the identical hardware
> > (accessing the /dev/raw/raw0, which maps to /dev/hdb) and I got ~38.4MB/s
> > raw write speed (BTW I get ~38.4MB/s from both Linux and FreeBSD when I do
> > the single-process raw sequential read test).
>
> I'm a bit confused, where do the numbers differ and what are the numbers?
The numbers from simple runs (standard chunk size, single I/O thread,
sequential read and then sequential write) are provided below. The
FreeBSD write number is less than half of what Linux is getting.
-Kevin.
Linux running rawio:
--------------------
Linux# time ./rawio -p 1 -s 8000000000 -r -w /dev/raw/raw1
Random read Sequential read Random write Sequential write
ID K/sec /sec K/sec /sec K/sec /sec K/sec /sec
aw1 38406.8 2344 38656.5 2359
real 0m15.946s
user 0m0.010s
sys 0m1.790s
FreeBSD running rawio:
----------------------
FreeBSD# time ./rawio -p 1 -s 8000000000 -r -w /dev/ad1
Random read Sequential read Random write Sequential write
ID K/sec /sec K/sec /sec K/sec /sec K/sec /sec
ad1 38410.4 2344 15732.6 960
26.06 real 0.00 user 1.18 sys
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