[luau] INFO: Heavy duty storage needs

[MonMotha]

Just curious if someone would like to stick this on the MPLUG wiki as a 
ATA/IDE vs SCSI thing under the hardware section (since I just noticed 
there is one).  Someone commented that they liked my explaination.

--MonMotha

MonMotha wrote:
> This is true.  In terms of raw I/O speed, IDE drives have caught up with 
> SCSI.  The reason?  The bus is no longer the bottleneck.  Even the best 
> of SCSI drives would have trouble saturating a 100MB/sec bus (though 
> SCSI is 160).  If all you need is raw I/O speed (which is a good chunk 
> of what your average single user desktop will be working with, 
> especially if they're doing a lot of multimedia), IDE drives are a great 
> choice (especialy combined with a software RAID solution, such as the 
> Linux software RAID or some of the software "RAID" cards that are now 
> out for the 'dozers).
> 
> SCSI shows it's strength in Tagged Command Queueing.  Unlike IDE 
> devices, SCSI drives can work on more than one command at the same time, 
> queueing them up in the best way possible.  For example, an IDE system 
> where a person wants to simultaneously (quicker than a single seek on 
> the drive) pull information from 10 places on the disk will have to do 
> them in the order the system says.  With SCSI, the system can send all 
> 10 (or usually 9) requests in quick succession, and the drive will 
> service them in the best way possible, minimizing redundant seeking, 
> serving out of cache when possible (often even during a seek for the 
> next command in the queue), etc.  In multiuser environments, this can 
> give SCSI a HUGE advantage over IDE.  SCSI drives also tend to have 
> lower seek times, often due to smaller platter sizes rotating at 
> significantly faster speeds (15,000 RPM vs. 7200 or even 5400 RPM). This 
> is also the reason SCSI drives tend to have smaller capacity as compared 
> to IDE drives while still being expensive.  The same "technology" has to 
> be used to pack all those bits into a small space, but the overall space 
> is smaller (many SCSI drives could almost fit their platters into 2.5" 
> laptop HDD enclosures, see fujisu specs on platter size).  These lower 
> seek times also help performance in multiuser environments.
> 
> Also, though this is not as much of a deal with UDMA IDE, IDE uses the 
> CPU for some of it's processing.  The same things are done on SCSI on 
> the dedicated controller and onboard the drive itself.
> 
> Conclusion: Don't assume SCSI is better, but don't assume raw I/O 
> bandwidth is the only measure of a hard drive.
> 
> --MonMotha
> 
> R. Scott Belford wrote:
> 
>> If you intend to record most or all of the traffic moving over your 
>> network, you need to spend as much time thinking about your disk 
>> subsystem as your processor and Ethernet card. Last year Sandstorm 
>> spent several months comparing IDE drives with the UDMA100 interface 
>> to SCSI LVD-160 drives. We also explored a variety of RAID systems. 
>> The conclusion: today's IDE drives are significantly faster than SCSI 
>> drives costing two or three times more per gigabyte stored.
>>
>> This is not the result we were expecting, and it goes directly against 
>> the conventional wisdom that says SCSI is inherently better than IDE. 
>> Nevertheless, it does seem to be the ugly truth, at least for 
>> straightforward read/write tests in a single-user environment. 
>> Although we saw the highest performance with a hardware-based RAID 5 
>> system manufactured by _Advanced Computer & Network Corporation_, we 
>> saw nearly the same performance with a RAID 5 system based on the 
>> _3Ware Escalade 7000_ RAID controller.
>>
>> from an article about network data capture at
>>
>> http://www.oreillynet.com/lpt/a//network/2002/04/26/nettap.html
> 
> 
> 
> _______________________________________________
> LUAU mailing list
> LUAU at videl.ics.hawaii.edu
> http://videl.ics.hawaii.edu/mailman/listinfo/luau
>