My disks... My system has 14 disk drives. At 65Meg per second they are only doing about 5 meg per second each. 6 of the disks are on a 40MB/second SCSI bus, this limits my overall speed. During a re-sync I get about 6 Meg/second per disk. My system... 2 CPUs help. It's a Dell. :) It is what they call a workstation. The chipset is Intel 440BX (going from memory, so not 100% sure). In its day it was a high end system. It has SD ram. 100 Mhz system bus. All memory slots are full with the same size DIMMs, so it can interleave if the chipset supports that. The chipset has 3 PCI buses. Since my overall speed is not exceeding the speed of 1 PCI bus, I don't think this helps me, but maybe it does. Everything is SCSI, I don't know if that helps. My disks are on 3 different SCSI busses, 2 Adaptec cards and 1 built-in Adaptec chipset. This may help, it is a Dell Precision Workstation 410. http://support.dell.com/support/edocs/systems/deqkmt/specs.htm If my system is so much faster because of the motherboard design, then cool! I did not know motherboard design could make such a difference. The test "hdparm -tT /dev/md2" used about 35% of both CPU's. The test is so quick it is hard to be sure about the cpu load. I have 17 disks overall, so I tried hdparm of all of my disks at the same time. This uses 100% of my CPUs. I don't understand how this can report such high speeds on my 6 disks on the slow SCSI bus. Timing buffer-cache reads: 128 MB in 11.18 seconds = 11.45 MB/sec 128 MB in 11.03 seconds = 11.60 MB/sec 128 MB in 10.97 seconds = 11.67 MB/sec 128 MB in 10.91 seconds = 11.73 MB/sec 128 MB in 11.43 seconds = 11.20 MB/sec 128 MB in 11.37 seconds = 11.26 MB/sec 128 MB in 11.35 seconds = 11.28 MB/sec 128 MB in 11.37 seconds = 11.26 MB/sec 128 MB in 11.45 seconds = 11.18 MB/sec 128 MB in 11.97 seconds = 10.69 MB/sec 128 MB in 11.78 seconds = 10.87 MB/sec 128 MB in 11.99 seconds = 10.68 MB/sec 128 MB in 12.26 seconds = 10.44 MB/sec 128 MB in 12.18 seconds = 10.51 MB/sec 128 MB in 11.84 seconds = 10.81 MB/sec 128 MB in 11.84 seconds = 10.81 MB/sec 128 MB in 12.43 seconds = 10.30 MB/sec Timing buffered disk reads: 64 MB in 9.42 seconds = 6.79 MB/sec 64 MB in 9.62 seconds = 6.65 MB/sec 64 MB in 9.95 seconds = 6.43 MB/sec 64 MB in 9.71 seconds = 6.59 MB/sec 64 MB in 10.17 seconds = 6.29 MB/sec 64 MB in 11.00 seconds = 5.82 MB/sec 64 MB in 11.45 seconds = 5.59 MB/sec 64 MB in 10.81 seconds = 5.92 MB/sec 64 MB in 11.20 seconds = 5.71 MB/sec 64 MB in 11.57 seconds = 5.53 MB/sec 64 MB in 10.89 seconds = 5.88 MB/sec 64 MB in 11.73 seconds = 5.46 MB/sec 64 MB in 11.27 seconds = 5.68 MB/sec 64 MB in 11.20 seconds = 5.71 MB/sec 64 MB in 12.18 seconds = 5.25 MB/sec 64 MB in 11.41 seconds = 5.61 MB/sec 64 MB in 11.91 seconds = 5.37 MB/sec This is from a single disk: Timing buffer-cache reads: 128 MB in 0.87 seconds =147.13 MB/sec Timing buffered disk reads: 64 MB in 3.51 seconds = 18.23 MB/sec When I test a single disk, they all perform about the same. A single disk "buffer-cache" performs better than any of my SCSI buses. I have 2 at 80 Meg/sec and 1 at 40 Meg/sec. The speed exceeds the speed of the PCI bus. Ok, I understand. I was thinking buffer-cache was the disk drive's on-board cache, but buffer-cache is the Linux disk cache. I think! Now I wonder why it is so slow! :) Anyway, I hope I gave you too much information! :) Guy -----Original Message----- From: TJ [mailto:systemloc@xxxxxxxxxxxxx] Sent: Saturday, December 04, 2004 10:24 AM To: linux-raid@xxxxxxxxxxxxxxx Cc: Guy Subject: Re: Looking for the cause of poor I/O performance On Thursday 02 December 2004 10:54 pm, Guy wrote: > My linux system is a P3-500 with 2 CPUs and 512 Meg RAM. My system is much > faster than my network. I don't know how your K6-500 compares to my > P3-500. > My array gives about 60MB /second. Now I'm extremely curious to know why your box does so much better than mine. Does the bus run at 100? 133? I'm guessing it's SDRAM, not DDR. Also, does it have a stock PCI bus, or something special? TJ Harrell - 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
