In tip 2247, we discussed setting Transfer Mode to DMA if available.
On the Disk Properties tab of your Disk Drives, you can check Write Cache Enabled. This enables the hard disk write-back cache. You will receive a warning about possible system damage or data loss which could occur if a power failure prevents flushing the cache to disk. This is a hardware option and is independent of the OS. If you have a UPS, this would be a safe option to enable.
On the SCSI Properties tab of your Disk Drives, you can Disable Tagged Queuing. Tagged queuing is performed by the SCSI controller (via the driver). This function sorts outstanding commands to reduce seek time. Disabling tagged queing will reduce overall disk performance. If you suspect your device is having trouble with overlapped requests, check Disable Tagged Queuing.
On the SCSI Properties tab of your Disk Drives, you can Disable Synchronous Transfers. Data transfered over SCSI cables can be use Synchronous mode, allowing multiple transfers to occurs before receiving acknowledgements, or Asynchronous mode, which is slower, but safer. If you suspect that your device is have trouble with synchronous transfers, try disabling it.