Disabling write-behind on IDE drives, and SMART
Jim C. Nasby
decibel at decibel.org
Fri Jan 21 22:36:00 PST 2005
On Fri, Jan 21, 2005 at 11:09:01AM -0800, Don Lewis wrote:
> On 21 Jan, Erik Trulsson wrote:
> > On Fri, Jan 21, 2005 at 08:31:06AM -0800, Kevin Oberman wrote:
> >> For servers that lack solid backup power (not a 10 minute
> >> UPS), I would probably turn it off. But for most systems it is probably
> >> worth the risks.
> > A 10 minute UPS should be plenty for that purpose. All that is needed
> > to protect against the risks of write-caching is for the server to be
> > able to make an orderly shutdown, which should not take more than a
> > couple of minutes. (If you need constant uptime, you need better power
> > backup, but that is a different issue.)
> I guess that you haven't had as many UPS failures as I have had. The
> usual problem is sudden battery and unexpected battery death which
> brings the UPS runtime close to zero.
> The UPSes definitely help with the short hits to the power, but for
> anything important I pay the outrageously high premium for SCSI disks
> and turn off write caching. At least SCSI has working tagged command
> queuing that when used with softupdates avoids the performance hit
> caused by turning off write caching, at least for most workloads.
Does SATA support an equivalent to tagged queuing?
Jim C. Nasby, Database Consultant decibel at decibel.org
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