SUMMARY: Enabling sweep cycles on Sabre disks

From: Art Hays - PSTAFF (lsr-vax!art@uunet.UU.NET)
Date: Mon Mar 09 1992 - 20:41:38 CST


> About two years ago when I installed my Seagate Sabre 1.2Gbyte drives
>(old Imprimis 9720) on Xylogics 753/7053 controllers, the conventional wisdom
>was to disable the sweep cycle option on the drives. Is this still the case?
>I will summarize.


        There were 6 replies. 5 of the replies say that it is still a good
idea to disable the sweep cycles. Some of these replies stated that with
sweep cycles enabled, the operating system prints error messages to the
effect that the heads aren't on cylinder.

        One reply leaves open the possibility of enabling the sweep cycles:

uunet!elroy.Jpl.Nasa.Gov!david (David Robinson) writes:
> The big problem with the sweeping is that if it is not configured right
> the sweep leaves the head on a different track than the controller
> thinks it's on. On the next read it will error when it discovers
> this discrepancy.
> There are a couple solutions, the first and easiest is to completely
> disable sweeps. Most Unix filesystems get enough activity that the
> extra sweep doesn't make too much difference, it was designed to
> increase the lifetime of the disk by accessing all tracks. The second
> approach is to configure it to still do the sweeps but enable the option
> to always return to the track that it started out on. This will eliminate
> any errors.

        I checked in my Sabre manual, and there are jumper settings that cause
the drive to return the head to the original cylinder after sweeping. There is
also another mode that results in sweeps being initiated only when the drive receives
a command to seek to a new cylinder- the sweep is snuck in between, and the heads
wind up on the new cylinder after the sweep.

Art Hays, Nat. Eye Institute, uunet!lsr-vax!art
Nat. Institutes of Health, Bethesda, MD (301) 496-7143

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