Disk Performance Issues

[Josh Paetzel]

On Tue, Apr 22, 2003 at 09:29:23PM -0400, Bill Moran wrote:
> Josh Paetzel wrote:
> >I've got a FreeBSD 4.8-STABLE system with a Maxtor 6L040J2 ATA/133 7200 
> >RPM IDE OS drive in it on a gigabtye GA-7VRXP motherboard.  I've also got 
> >a pair of Western Digital WD800BB 7200 RPM ATA/100 drives in RAID 1 on an 
> >onboard Promise 20276 ATA/133 RAID Controller.  
> >
> >atacontrol reports that all the drives are being properly probed:
> >
> >===root at markx ('tty') /storage/os_isos -> atacontrol mode 0
> >Master = UDMA133 
> >Slave  = ???
> >===root at markx ('tty') /storage/os_isos -> atacontrol mode 1
> >Master = PIO4 
> >Slave  = PIO4
> >===root at markx ('tty') /storage/os_isos -> atacontrol mode 2
> >Master = UDMA100 
> >Slave  = ???
> >===root at markx ('tty') /storage/os_isos -> atacontrol mode 3
> >Master = UDMA100 
> >Slave  = ???
> >
> >
> >My issue is that I'm seeing sustained transfer rates on 600-700 meg files 
> >in the 5-6 Meg/second range...about 1/4 of what the drives are capable of. 
> >Does anyone have any advice on where to go from here in troubleshooting 
> >this issue?
> 
> You're reading the specs wrong.  That drive is not capable of sustained 
> through-
> put of 133mb/s.  According to the data sheet, it can only do 44mb/s 
> sustained.
> That seems to be about what you're getting.  The ATA133 interface will only
> go at 133 until the drive's buffers fill up, then it has to slow down to 
> match
> the actual speed the drive can transfer data to/from the platters.  Some of 
> the
> higher-end SCSI drives are capable of sustained speeds that high, but I 
> don't
> know of any 7200 RPM drives that can touch it.  Maxtor makes a 15000 RPM 
> drive
> that can (purportedly) sustain 75megabytes/sec. (wow!)
> 
> -- 
> Bill Moran
> Potential Technologies
> http://www.potentialtech.com

http://www.dartek.com/printablespecs.cfm?ItemNo=79374

This claims my ATA/100 drives are capable of sustained data transfer of 52.5 
Megs/sec.  I don't think that's very accurate...most of the benchmarks I've 
seen are in the 20-30 Meg/sec range for modern ata/100 and 133 drives.  5 
Megs/sec is NOT normal performance however.  These numbers I'm throwing about 
all refer to susstained transfer rates on large files.

Josh