On Thu, 2005-07-14 at 11:16 +1000, Neil Brown wrote: > On Wednesday July 13, mingz@xxxxxxxxxxx wrote: > > On Thu, 2005-07-14 at 08:38 +1000, Neil Brown wrote: > > > On Wednesday July 13, jdc@xxxxxx wrote: > > > > Here's a question for people running software raid-5: do you get > > > > significantly better read speed from a raid-5 device than from it's > > > > component partitions/hard drives, using the simple dd test I did? > > > > > > SCSI-160 bus, using just 4 of the 15000rpm drives: > > > > > > each drive by itself delivers about 67M/s > > > Three drives in parallel deliver 40M/s each, total of 120M/s > > > 4 give 30M/s each or a total of 120M/s > > > > > > raid5 over 4 drives delivers 132M/s > > why here a 132MB/s instead of 120MB/s (3 * 40MB/s) as u mentioned? any > > factor lead to this increase? > > > > > > I did another test over 10 times the amount of data, and for 34M/s for > 4 concurrent individual drives, which multiplies out to 136M/s. The > same amount of data of the raid5 gives 137M/s, so I think it was just > experimental error. ic. thanks for explanation. yes, agree. it seems that u can get a near linear performance with decent SCSI HW while what we can get from SATA is not good. :P Ming > > NeilBrown - To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
