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On Sun, 24 Nov 2002 18:56, Васил Колев wrote:
> About performance - IDE still uses a lot of the CPU, SCSI has it's own
> processing power.

Please do some benchmarks.  You'll discover that when DMA is enabled and you 
have a good chipset then IDE will not use much CPU.

OTOH if you have an Adaptec 1510 then even accessing a CD-ROM will take 
excessive amounts of CPU time.

In summary:  Good controllers use little CPU time, bad controllers use a lot 
of CPU time.  Doesn't matter whether it's IDE or SCSI.

> You can put a lot more disks on a single SCSI
> controler, than on a IDE controler, and there (afaik, i could be
> mistaken) two drives on one bus cannot work simultaneously and share the
> bandwidth (which isn't a problem with SCSI, if you have 160 MB/s bus,
> and 3 disks that can make about 40MB/s, you can have all 120MB/s)

3ware IDE controllers support up to 12 drives.  You won't find many SCSI 
controllers that can do that and deliver acceptable performance (you won't 
get good performance unless you have 64bit 66MHz PCI).

Do a benchmark of two IDE drives on the one cable and you will discover that 
the performance loss is not very significant.

ATA-133 compared to Ultra2 SCSI at 160MB/s is not much difference.  S-ATA is 
coming out now and supports 150MB/s per drive.

Please do some benchmarks before you start talking about performance.

> And maybe i should say something about the reliability, SCSI disks don't
> die that often, compared to IDE drives, while being used a lot 24x7.

The three biggest causes of data loss that I have seen are:
1)  Incompetant administrators.
2)  Heat.
3)  SCSI termination.

SCSI drives tend to have higher rotational speeds than IDE drives and thus 
produce more heat.  Even when IBM was shipping thousands of broken IDE hard 
drives (and hundreds of broken SCSI drives which didn't seem to get any 
press) the data loss caused by defective drives was still far less than any 
of those three factors.

http://www.coker.com.au/selinux/   My NSA Security Enhanced Linux packages
http://www.coker.com.au/bonnie++/  Bonnie++ hard drive benchmark
http://www.coker.com.au/postal/    Postal SMTP/POP benchmark
http://www.coker.com.au/~russell/  My home page

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