![]() | |||||||||||
Messages in this thread |
On Mon, May 30 2005, Greg Stark wrote: > > ATA has a limitation of 32 tags, so queued write cache off won't beat > > unqueued write cache on in any modern drive. > > People earlier were quoting 30-40% gains with NCQ enabled. I assumed > those were with the same drive in otherwise the same configuration, > presumably with write-caching enabled. If you are talking about the numbers I quoted, those were for random read performance. > Without any form of command queueing write-caching imposes a severe > performance loss, the question is how much of that loss is erased when > NCQ is present. I'll try some random write tests with write caching disabled. > People actually tend to report that IDE drives are *faster*. Until > they're told they have to disable write-caching on their IDE drives to > get a fair comparison, then the performance is absolutely abysmal. The > interesting thing is that SCSI drives don't seem to take much of a > performance hit from having write-caching disabled while IDE drives > do. NCQ will surely lessen the impact of disabling write caching, how much still remains to be seen. You could test, if you have the hardware :) Real life testing is more interesting than benchmarks. -- Jens Axboe - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||
| Last update: 2005-05-30 08:36 [from the cache] ©2003-2008 | |||||||||||