AHCI timeouts - 8.1-PRERELEASE
dewayne.geraghty at heuristicsystems.com.au
Mon Jun 7 05:15:04 UTC 2010
Following extensive testing, I've recommended to Alexander, in a
longer email, that the default for VIA's VT8251 AHCI Controller
be set at AHCI_Q_NOPMP|AHCI_Q_NONCQ
Use of ahci in the kernel without this option will result in timeouts,
ultimately preventing the machine from performing IO. No timeouts
occurred when the ahci driver was removed from the kernel.
Approx 35 tests were applied, simultaneously copying a large number
of files (~2000) to 8 partitions that ranged in size from 10B to 1.6GB.
Testing included single and gmirror disks.
The removal of NCQ resulted in a degraded performance of < 8% when
compared against EDGEIS, which failed under gmirror testing.
Performance under load without NCQ was better than a kernel
The test was conducted on a VIA SN18000 using two WD500GB-AAKS disks,
the disks were repartitioned (gpart) and system rebooted before each test.
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