Messages in this thread | | | Date | Tue, 26 Apr 2005 10:12:59 -0600 | From | Grant Grundler <> | Subject | Re: [PATCH] PCI: Add pci shutdown ability |
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On Tue, Apr 26, 2005 at 02:30:12PM +1000, Benjamin Herrenschmidt wrote: > Additionally, some machines won't properly park/flush the disk, it's > necessary to send the proper suspend commands to IDE hard disks prior to > shutting down or we risk data loss.
That sounds like the disk is caching write data.
SCSI has a "Write Cache Enable" bit in the "caching mode page". See "scsiinfo -c" output.
10 years ago I measured/compared performance of disabling WCE (plus queue depth of 8) and enabling WCE (queue depth 1). It's a wash for the workloads I was testing. I was told "stupid OSs" that didn't know about tagged queueing needed WCE for benchmarks. HP cared for exactly the same reasons: Bus Resets or Disk power failure would cause data loss with WCE enabled.
Disabling WCE on current OSs would solve the above problem IFF IDE/SATA also supports "cache mode" page.
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