Cory Petkovsek wrote: > With this software raid 5 config, and only ultra 10k drives, I can > read at about 29-30mb/sec (with dd). > On my other server, it has 6 ultra160 15kRPM in a hardware raid 1+0 > config, I can only read at 40mb/sec. :( Sad. This is using Adaptecs > 3200S (DPT Rebranded) RAID controller. I think this should be at > least 80mb/sec! Sequential read rate is not a particularly interesting measure. Unless you're serving up astronomy datasets, your disks are probably spending more time seeking than reading. Just for grins, I wrote a couple of little programs to measure a disk's sequential read rate and its seek rate. Try running these on your RAIDs - I bet they do a lot better on seeking than my disks. Here's what happens when I run 'em on my personal workstation (-: , an aging 450 MHz PII, 440BX/PIIX4 system with two 7200 RPM UltraATA/33 drives. (Note that UltraATA/100 is the current standard.) # dmesg | grep '^hd[ab].*/' hda: IBM-DTLA-307045, 43979MB w/1916kB Cache, CHS=5606/255/63 hdb: IBM-DJNA-372200, 21557MB w/1966kB Cache, CHS=2748/255/63 # ./throughput /dev/hda /dev/hdb /dev/hda: 1 Gbytes in 48.8933 seconds: 20.9436 Mb/second /dev/hdb: 1 Gbytes in 60.1947 seconds: 17.0115 Mb/second 0.010u 25.080s 1:49.10 22.9% 0+0k 0+0io 101pf+0w # ./throughput /dev/hda & ./throughput /dev/hdb & wait /dev/hda: 1 Gbytes in 71.1773 seconds: 14.3866 Mb/second /dev/hdb: 1 Gbytes in 71.1719 seconds: 14.3877 Mb/second # ./seeks /dev/hda /dev/hdb /dev/hda: 32768 seeks in 240.949 seconds: 135.996 seeks/second, 7.35318 ms/seek /dev/hdb: 32768 seeks in 268.271 seconds: 122.145 seeks/second, 8.18699 ms/seek # ./seeks /dev/hda & ./seeks /dev/hdb & wait /dev/hdb: 32768 seeks in 514.204 seconds: 63.7257 seeks/second, 15.6923 ms/seek /dev/hda: 32768 seeks in 515.087 seconds: 63.6164 seeks/second, 15.7192 ms/seek What can we conclude? Two IDE disks get 28 Mb/sec sequential rate, which nearly equals the rate you got from 3 UltraSCSI drives. One IDE disk can seek 120-140 times a second, and two disks can seek 125 times a second. How many seeks/second can you get on your RAIDs? -- Bob Miller K<bob> kbobsoft software consulting http://kbobsoft.com [EMAIL PROTECTED]
