paul at clubi.ie wrote:
> I understand why SCSI is used a lot for RAID, and I agree with you
> that reliability is only one small reason.
>> You need to stop conflating IDE and SATA though (e.g. SAS is SATA phy
> with SCSI command protocol over it - you sometimes can plug SATA
> drives into SAS bays).
>SAS is a different beast from ordinary Consumer SATA, A cheap SATA PIDE
adaptor won't give you SAS. I think you will find than almost all
consumer PCs / Mobos that allege to offer SATA RAID, that it is RAID0 or
RAID1 and in SW (inside the driver). Not HW (i.e. its own CPU & RAM) and
not RAID5.
I was only talking about a cheap cluster, using two external shelves and
two channels of SCSI on two host controllers. I suppose 10 year old
tech, but very cheap and indeed not scalable.
If you want reliability over performance SW RAID1 is best as the OS will
still boot on any ordinary controller with 1 disk. RAID5 definitely
needs some overall system thought. RAID 0 is very bad idea as for a
small improvement you are twice as likely to lose everything.
A basic UPS is about 100 Euro and s/h AMI Megaraid PCI card about £15 on
eBay. But why are SCSI disks so much more expensive than ordinary SATA
or PIDE disks?
--
Mike
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