pci-e hardware raid controller

[C M Reinehr]

On Wednesday 06 June 2007 10:11, Net Llama! wrote:
> On Wed, 6 Jun 2007, vu pham wrote:
> > On Tue, 2007-06-05 at 14:50 -0500, Net Llama! wrote:
> >> On Tue, 5 Jun 2007, Vu Pham wrote:
> >>
> >> SW RAID is generally as fast as the controller its sitting on.  You
> >> shouldn't assume that HW RAID is faster than SW RAID.  Also, most people
> >> looking to use RAID solutions aren't doing it for better performance.
> >
> > I think raid 0 boosts the disk performance pretty well. I had two
> > workstations each had a single scsi disk. After I add 3 more hdds onto
> > each workstation and use raid-0, I can see all the apps are loaded much
> > faster.
>
> Sure, but RAID0 is just a big virtual disk.  So the performance is going
> to be about the same as the disks themselves.  Its RAID1 and up where
> things get alot more interesting in terms of performance.
>
> > Raid 0 has more possibility of disk failure so I backup my two
> > workstations everyday.
>
> That's why RAID0 is little more than a toy from a reliability perspective.
> RAID5 tends to be the trade-off point between the features of RAID 1 and
> RAID0.  Of course there's also RAID 0+1 which has better performance than
> RAID5, assuming that you  have enough disks in the arrya.
>
> > I am going to try the LVM. If the performance gain is good enough then I
> > do not have to use the hardware raid and can  get more memory for my
> > wks :)
>
> I'm puzzled why anyone thinks that LVM is a substitute for RAID.  THey
> serve different purposes, and have little in common.

	RAID 0, strictly speaking is not RAID--it's not redundant. LVM, obviously, is 
not a substitute for true RAID, but Vu did not express an interest in 
redundancy, only stripping to increase performance. And, LVM can do stripping 
to increase performance.

	As you say, RAID1+0 is better, as it provides both stripping and RAID, which 
is what I use, actually md/RAID10.

Cheers!

cmr
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Debian 'Etch' - Registered Linux User #241964
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