2nd hard disk for MySQL/PostgreSQL database under RedHat 7.2

[mcmanus at ducksong.com (Patrick R. McManus)]

[Jerry Feldman: Mon, Feb 25, 2002 at 11:24:58AM -0500]
> SCSI vs. EIDE.
> JABR mentiuoned that it is best to use SCSI if one has a SCSI controller. However, I remember 
> seeing recently that IDE (or EIDE) today will give you just as good performance. 

I don't want to bash IDE and the fact that they are a good deal for
the normal desktop.. but to say that they will give you performance
even competitive with scsi is not my experience at all.

typical scsi throughput is 35MB/s.. cheetah's will do 40.. typicaly
udma/100 IDE performance (if you've got a chipset driver to support
DMA at that rate, which depends on your controller under linux) is
25.. I think the best I've come across is 30..

scsi seek times are typically much faster too.. western digital's ide
caviar drives (ata/100) are 8.9ms and their corresponding 7200-spin
scsi drives are 6.9.. that's a 25% difference and in a seek-intensive
space like DB's you see that bigtime.

> 
> Today, IDE drives are still significantly less expensive than SCSI:
> eg. A 7200RPM 100GB EIDE drive is about $175, and  the largest SCSI I could find is 73.4GB 
> (10,000RPM) for about $465. 

yep.. $/MB is heavy in favor of IDE.. however, lots of times spindles
are just as impt as total MBs.. so you end up buying a fair number of
smaller drives instead of a single big one.. IDE is still cheaper, but
on the smaller drives the differential is a lot less and therefore
going cheap is less tempting..

> For a commercial server, I would certainly go SCSI (or possibly firewire...). But for a personal 
> system or a home based or even a lightly loaded commercial server, IDE is much more 
> economical. 

yep.

if your limiting factor is network - go ide.. but if parallel load is
your big issue - you'll do a lot more a lot faster with scsi.

-P