SATA or SCSI drives - Multiple Read/write speeds.

Alvin Oga alvin at Mail.Linux-Consulting.com
Mon Dec 8 18:15:24 EST 2003


hi ya robin/bill

On Mon, 8 Dec 2003, Bill Broadley wrote:

> In my experience there are many baises, religious opinions, and rules
> of thumb that are just extremely BAD basis for making these related
> decisions.  Especially since many people's idea about such things change
> relatively slowly compared to the actual hardware.

yupperz !!
 
> My best recommendation is to either find a benchmark that closely resembles
> your application load (Similar mix of read/writes, same level of RAID, same
> size read/writes, same locality) and actually benchmark.
> 
> I'm sure people can produce a particular configuration of SCSI, ATA, and SATA that 
> will be best AND worst for a given benchmark.

yupperz ... no problem ... you want theirs to look not as good, and our
version look like its better... yupp ..

definite yupppers one do a benchmark and compare only similar environments
and apps ... otherwise one is comparing christmas shopping to studing
to be a vet ( benchmarks not related to each other )

-----

for which disks ...
	- i'd stick with plain ole ide disks
	- its cheap
	- you can have a whole 2nd system to backup the primary array
	for about the same cost as an expensive dual-cpu or scsi-based
	system

for serial ata ...
	- dont use its onboard controller for raid ... 
	- it probably be as good as onboard raid on existing mb...
	( ie ... none of um works right 
		works == hands off booting of any disk 
		works == data resyncs by itself w/o intervention

		but doing the same tests w/ sw raid or hw raid
		controller w/ scsi works fine

> So I'd look at bonnie++, postmark, or one of the other opensource benchmarks
> see if any of those can be configured to be similar to your workload.  If not
> write a benchmark that is similar to your workload and post it to the list asking
> people to run it on their hardware.  The more effort you put into it the
> more responses your likely to get.  Posting a table of performance results
> on a website seems to encourage more to participate.

other benchmark tests you can run ....

	http://www.Linux-1U.net/Benchmarks

other tuning you can to to tweek the last instruction out of the system

	http://www.Linux-1U.net/Tuning
 
> There are no easy answers, it depends on many many variables, the type
> of OS, how long the partition has been live (i.e. fragmentation),
> the IDE/SCSI chipset, the drivers, the OS, even the cables can have
> performance effects.

(look for the) picture of partitions/layout ... makes  big difference

	http://www.Linux-1U.net/Partition/

> The market seems to be going towards SATA, seems like many if not all major
> storage vendors have an entry level SATA product, I've no idea if this
> is just the latest fad or justified from a pure price/performance perspective.

if the disk manufacturers stop making scsi/ide disks .. we wont have
any choice... unless we go to the super fast "compact flash"
and its next generation 100GB "compact flash" in the r/d labs 
which is why ibm sold its klunky mechanical disk drives in favor
of its new "solid state disks"  ( forgot its official name )

c ya
alvin

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