Messages in this thread | | | Date | Sat, 16 Nov 2002 01:16:41 +0100 | From | Matthias Andree <> | Subject | Re: IDE TCQ |
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On Wed, 13 Nov 2002, Jens Axboe wrote:
> > Second set of questions: Does it do any good to one-channel-one-disk > > setups? Is it supposed to do good to access time, operations/sec, > > throughput, random reqs rearrangement or what? Do you have any > > figures how much TCQ helps performace (e.g. in file serving case)? > > Yes it will help any setup. Due to way ide tcq works, it's recommended > only to use tcq on one drive on a channel right now. This may change in > the future.
Would be "it's recommended to use only one drive on a channel for best results, whether with or without TCQ" more accurate? Or are there reasons that make TCQ <-> slave interactions particularly bad that don't show up without TCQ?
> I don't have any general numbers. I did some benchmarking when I first > implemented it, and it typically shows (as with scsi drives) that having > just enough tags to keep the disk busy helps a bit. The linux io > scheduler does the rest. For random reads, 10-30% speed increase was > observed.
Did you perchance benchmark the impact TCQ has on sequential writes when the write cache is turned off?
Turning off the write cache without TCQ has a severe impact (30 to 70% on my "stupid dd" tests) in my computer (VIA82C686, but I don't recall which drive I did this on, it was either of IBM DJNA, DTLA or Maxtor 4W060H4) - 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/
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