Messages in this thread | | | Date | Sun, 24 Jun 2007 12:59:10 -0400 (EDT) | From | Justin Piszcz <> | Subject | Re: SATA RAID5 speed drop of 100 MB/s |
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On Sun, 24 Jun 2007, Michael Tokarev wrote:
> Justin Piszcz wrote: >> Don't forget about max_sectors_kb either (for all drives in the SW RAID5 >> array) >> >> max_sectors_kb = 8 >> $ dd if=/dev/zero of=file.out6 bs=1M count=10240 >> 10737418240 bytes (11 GB) copied, 55.4848 seconds, 194 MB/s >> >> max_sectors_kb = 128 >> 10737418240 bytes (11 GB) copied, 22.6298 seconds, 474 MB/s > > Well. You're comparing something different. Yes, this > thread is about linux software raid5 in the first place, > but I were commenting about [NT]CQ within a single drive. > > Overall, yes, the larger your reads/writes to the drive > becomes, the faster its linear performance is. Yet you > have to consider real workload instead of very synthetic > dd test. It may be good approcsimation of a streaming > video workload (when you feed a large video file over > network or something like that), but even with this, > you probably want to feed several files at once (different > files to different clients), so single-threaded test > here isn't very useful. IMHO anyway, and good for a > personal computer test. > > /mjt > - > To unsubscribe from this list: send the line "unsubscribe linux-ide" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >
Concerning NCQ/no NCQ, without NCQ I get an additional 15-50MB/s in speed per various bonnie++ tests.
# Average of 3 runs with NCQ on for Quad Raptor 150 RAID 5 Software RAID: p34-ncq-on,7952M,43916.3,96.6667,151943,28.6667,75794.3,18.6667,48991.3,99,181687,24,558.033,0.333333,16:100000:16/64,867.667,9,29972.7,98.3333,2801.67,16,890.667,9.33333,27743,94.3333,2115.33,15.6667 # Average of 3 runs with NCQ off for Quad Raptor 150 RAID 5 Software RAID: p34-ncq-off,7952M,42470,97.3333,200409,36.3333,90240.3,22.6667,48656,99,198853,27,546.467,0,16:100000:16/64,972.333,10,21833,72.3333,3697,21,995,10.6667,27901.7,95.6667,2681,20.6667
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