Given that this must be taken with a bit of a grain of salt: hdparm -tT /dev/hda Timing cached reads: 2820 MB in 2.00 second = 1409.91 MB/sec Timing buffered disk reads: 200 MB in 3.02 seconds = 66.31 MB/sec
hdparm -tT /dev/MD0 Timing cached reads: 2804 MB in 2.00 seconds = 1401.91 MB/sec Timing buffered disk reads: 346 MB in 3.01 seconds = 115.02 MB/sec This is with /dev/md0 being a RAID 0 array of two 250GB SATA drives, / dev/hda is a 250GB PATA drive alone on its controller channel. Brian Wood [EMAIL PROTECTED] On Jan 9, 2006, at 1:36 PM, Johnathon Meichtry wrote: > James, > > Thanks, I was putting it in layman's terms but your right I should > have been > more precise. > > If one was going to be technically correct then it isn't even that > straight > forward as with most systems you will probably have three random > access > reads for every sequential write therefore with RAID0 you may get an > alternating disk write (some would say simultaneous but really > there is no > such thing as there is only one bus) but between them you will > probably have > three reads with two probably being on the same disk therefore > RAID0 only > giving you a marginal performance improvement without even taking into > account disk 1 and disk 2 being on the same controller (i.e. IDE > PATA master > and slave) and the resultant IO wait (not to mention the bottleneck > on the > PCI bus). > > To me striping is one of the things where it looks great in theory > but not > until you have three or more disks across multiple controllers do > you get a > real-world noticeable performance improvement. Not that I am > knocking RAID0 > but I believe that all it gives you is aggregation of partitions > and not > much else so you might as well have at least three or more disks/ > slices and > go for RAID5 so that if you lose one you don't lose the lot and you > have a > better chance of getting a performance improvement. > _______________________________________________ mythtv-users mailing list [email protected] http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
