Two RAID 0 questions

Rick Stevens rstevens at vitalstream.com
Wed Feb 25 20:44:11 UTC 2004


Alexander Dalloz wrote:
> Am Mi, den 25.02.2004 schrieb Allan Metts um 14:46:
> 
>>At 05:29 AM 2/25/2004, Alexandre Oliva wrote:
>>
>>
>>>Yes.  IDE doesn't permit simultaneous access to disks on the same
>>>controller.  Well, you could make do with two disks on a single
>>>controller, but performance would be terrible.
>>
>>
>>Okay, two IDE identical drives -- one will be the Master on the Primary 
>>controller, the other will be the Master on the Secondary controller.
>>
>>Next question: Will it hurt anything to put the CDROM drive as the Slave on 
>>the secondary controller?  This is a no-no in the SCSI world, since I think 
>>it slows the entire bus down to the speed of the slowest device.  But I 
>>need a CDROM to actually install Fedora, and I'd rather not buy an 
>>additional controller....

That's not true.  99% of SCSI-based CDROMs support detatched operation.
It does not slow down the bus except when the CD-ROM is transferring
data.  Bus speed is managed by the handshake between the initiator and
the target.  If you have an ultra-SCSI disk on the same bus as a CD,
the bus will run at ultra-SCSI speed when the disk and controller are
talking and at the slow speed with the CD and controller are talking.

> It's no problem to have a CD-ROM as slave together with a harddrive on
> the same controller. It will not slow down the whole controller.

That's also true.  IDE and SCSI are handled by a handshake and speed
negotiation.  The bus adapts speeds based on what's talking to what.
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- Rick Stevens, Senior Systems Engineer     rstevens at vitalstream.com -
- VitalStream, Inc.                       http://www.vitalstream.com -
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-      "Doctor!  My brain hurts!"  "It will have to come out!"       -
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