On Tue, 2 Aug 2005, Boik Moon wrote: > Hi, > > According to RAID theory, the READ performance with RAID0, 1 and 5 > should > Be faster than one with non-RAID. I tested it on Redhat linux(ES) on > Pentium PC, but they are almost same. I am using > RocketRAID404(HPT374)PCI card to connect 4 master IDE > Drivers. > Ideally it must be 2 or more times faster on RAID0/1/5. Why must it be? There was a discussion about this here recently IIRC... Maybe the archives have the full details. I'm assuming you are using software RAID here and not what the card supports... You should be able to see a speed-up with RAID-0, but with the other levels, it's not always obvious. My experiences are that in general, I don't see a speed-up with RAID-1. I tend to test systems with a RAID-0 array if possible though and then there usually is an obvious speed-up, but a lot depends on your hardware. If you have (eg) one card with 4 drives hung off it, then you might find that the PCI bandwdith is the bottleneck - if you want absolute preformance, you'd need a motherboard with separate PCI busses, etc. AIUI, RAID-1 will read 'chunksize' off one disk, then move to the next disk, although I'm not sure if the reads are/can be posted together. It probably depends on how much data you are readong off the filesystem at that time Do make sure you have DMA enabled on each drive/controler, etc. You should be able to use hdparm to check this - a modern drive should be able to sustain a read speed of between 50 and 60MB/sec... You'll see this drop down to 3-5MB/sec if theres no DMA... I also think YMMV is the phrase to use here... Good luck! Gordon - 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
