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Date: Sun, 11 Sep 2016 17:54:00 -0400 (EDT)
From: "Sean C. Farley" <scf@FreeBSD.org>
To: freebsd-stable@FreeBSD.org
Subject: Slow CD access until primed by readcd (cdrtools)
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I ran into an issue with at least a few CD's where the access to them 
mounted as cd9660 was very slow.  dd of /dev/cd0 was also slow.

However, if I run readcd (from cdrtools-devel-3.02a06,1) at least once, 
which would run at full speed, then any access to the disc whether 
mounted or not is at full speed.  I do not recall this happening in the 
past, but this is with a newer computer (i.e., newer drive).  It appears 
to be that something is determining the full speed correctly when readcd 
is run and is keeping that state until the disc is removed while 
mounting or running dd against the drive does not.

OS:  10.3-STABLE (r304921) amd64.

pass0: <HL-DT-ST BD-RE  WH16NS40 1.00> Removable CD-ROM SCSI device
pass0: 150.000MB/s transfers (SATA 1.x, UDMA6, ATAPI 12bytes, PIO 8192bytes)

Any ideas?

Sean
-- 
scf@FreeBSD.org