Clustering has always been a (small) win for the ATA/SATA hardware I have worked on. Many controllers read the scatter-gather list "on demand", so if clustering is not used, there are a lot of times where the controller must stop streaming data, and fetch the next s/g entry, then resume streaming data. Clustering reduces the number of such events, giving better bus utilization and (slightly) faster transfers. The more modern hardware I'm working with now will generally read the s/g table in larger blocks, so that it only rarely needs to interrupt data transfers to fetch s/g info. Clustering is not as big a win with this, but still reduces total bus cycles required. Cheers - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
