On Wed, 2004-06-02 at 17:07, Frank Smith wrote: > If it's linux, try using hdparm to verify the modes and speed of your > disk. Like Jon says, a good drive can have terrible performance if > it is running in the wrong mode.
hdparm is a nifty addition to my system monitoring toolkit (top, gnome's cpu monitor icon, sticking my ear close to a drive to listen for seeks, eyeballing the disk activity LED, and dump's data transfer messages). hdparm uncovered some interesting information. The 2 drives on this machine are identical and identically configured, except for one thing: both are using dma, but one of them, hda, is udma2 and hdc is udma5. I did a 'hdparm -X 69 /dev/hda' to set hda to udma5. hdparm said it did, but hdparm -i still said udma2. Jon implied that hdparm may be just kidding about this. hdparm -Tt gives the following: ---- /dev/hda: Timing buffer-cache reads: 2800 MB in 2.00 seconds = 1399.51 MB/sec Timing buffered disk reads: 82 MB in 3.00 seconds = 27.33 MB/sec /dev/hdc: Timing buffer-cache reads: 2772 MB in 2.00 seconds = 1386.21 MB/sec Timing buffered disk reads: 114 MB in 3.03 seconds = 37.62 MB/sec ---- Since I have no feel for what pio would be like, I don't know. But the difference looks ballpark right for the different dma modes. I looked at another system: an old Dell server downstairs with a Maxtor PCI IDE card and a 2 or 3 year old Maxtor 60GB disk, also claiming to be udma5: ---- /dev/hde: Timing buffer-cache reads: 128 MB in 0.59 seconds =216.95 MB/sec Timing buffered disk reads: 64 MB in 1.59 seconds = 40.25 MB/sec ---- Something is wrong here. The disks up here are much newer, and a lot slower. I'm using the onboard controllers in an Intel D865GLC motherboard. > Also, make sure your kernel is using the correct chipset driver > for your IDE controller. On a machine at home I replaced the > motherboard and my disk speeds dropped to under 2MB/sec. I finally > figured out that since I had a different controller than the one I had > compiled in support for, the kernel had dropeed back to generic IDE > support. Rebuilding the kernel with the proper driver made an over 10X > performance boost. That's where I'm going next. Kernel dox, motherboard dox, Gentoo dox, and hdparm's man page. And google, of course... Does anyone know of an equivalent to hdparm -Tt for SCSI disks? -- Glenn English <[EMAIL PROTECTED]>
