pci-e hardware raid controller

[Vu Pham]

On Wed, 2007-06-06 at 14:34 -0500, C M Reinehr wrote:
> 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.
> 

In my particular case, I do not need redundancy at all. All I need is
performance. All the codes are CVSed every hour. The app and its
debugging tool are sometimes too slow (  I can notice a *lot* of disk
accessing at that time ). 

Vu