Date: Sun, 24 Nov 1996 19:08:20 -0700 (MST) From: Wes Peters <softweyr@xmission.com> To: chat@freebsd.org Subject: SCSI A/V drives (was Re: ATAPI) Message-ID: <199611250208.TAA00308@obie.softweyr.com> In-Reply-To: <199611232121.OAA19464@phaeton.artisoft.com> References: <199611231856.NAA03954@hill.gnu.ai.mit.edu> <199611232121.OAA19464@phaeton.artisoft.com>
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% What are these A/V drives I see nowdays? Are these just
% standard-issue SCSI drives trying to get on the 'multimedia'
% bandwagon, or is there really something else to them?
Terry Lambert writes:
> They are standard drives which do not have an off cycl;e for thermal
> recalibration.
>
> This makes them faster to dump an incoming stream of "A/V" data
> and turn around for more data, but it makes them much more sensitive
> to thermal variance.
>
> [...]
The big difference, in terms of usage, is that you cannot take a
normal disk drive and dump incoming video streams onto it. As the
heads begin moving back and forth across the disk it will heat up.
At this point, the disk will perform a thermal recalibration, costing
several seconds, and your video stream will be broken.
As Terry mentioned, for use as data disks, A/V disks will give you
more consistent performance if kept at a constant operating
termperature. If your machine experiences wide temperature variances,
which most PCs, with their poor-quality cases, power supplies, and
ventilation will, you may experience higher error rates.
I recommend using A/V drives in large server systems with several disk
drives and a good positive air flow through the case, especially for
high usage filesystems like a news spool. For workstations, any gain
is probably not worth the additional cost.
--
"Where am I, and what am I doing in this handbasket?"
Wes Peters Softweyr LLC
http://www.xmission.com/~softweyr softweyr@xmission.com
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