pci-e hardware raid controller

[C M Reinehr]

On Tuesday 05 June 2007 14:01, Vu Pham wrote:
> On Tue, 2007-06-05 at 10:06 -0500, C M Reinehr wrote:
> > On Tuesday 05 June 2007 08:50, Vu Pham wrote:
> > > I am looking for a sata pci-e *hardware* raid controller for Linux
> > > ( Suse 10.2 ). I mean the one that the Linux OS can see the whole raid
> > > system as one physical drive.
> > >
> > > This one will be use as a raid-0 with 4 SATA drives.
> > >
> > > Any recommendation ?
> > >
> > > Thanks,
> > >
> > > Vu
> >
> > Generally, when someone asks for help with a problem or information on a
> > product, I dislike receiving replies suggesting a different product. But,
> > now I'm going to do it. Why would you want to spend money to buy and
> > additional single point of failure, when you could accomplish the same
> > thing for free with LVM2 (logical volume management)?
> >
> > (Sorry, but I just couldn't help myself.)
>
> No problem, all advice ( and critics ) are welcome :)
>
> There are two reasons:
>
> 1. this is a test system for coding and I would like to have the highest
> disk access performance as much as possible, and I think the hardware
> raid is faster than software raid. Or is the gain so small to afford a
> hardware raid ?

	I have absolutely no experience here, but if I had to guess, I would think 
that a true, hardware based solution would, indeed, out perform a software 
based solution. Whether the difference would be significant or not would 
depend upon the load put upon the system.

> 2. With LVM, Linux will save the lvm configuration somewhere on disk and
> to fully restore the whole system, you have to prepare a similar lvm
> configuration in advance, right ? If I am only able to restore to a
> single disk, will the restore work ? I 've tried LVM only one or twice
> long time ago, so I think I am pretty much wrong on this.

	This would depend upon your backup solution. As far as any applications would 
be concerned, they would see only a single large partition. So, if you used 
tar, Bacula or some other, similar backup program you would just be copying 
files and could restore them anywhere that you chose. So, you could restore 
to a single disk or multiple disks.

	However, if you're talking about completely imaging the system, O/S & all, 
I'm not sure just what problems you would run into. Personally, my procedure 
is to backup my application files and my configuration files (/etc/*) and 
then do a minimum, new system install, creating a new volume management 
scheme, raid, etc. from scratch, and then restore my applications on top of 
it. But then, I only have a half-dozen or so systems to worry about.

	On the other hand, if your raid card should fail, you would have to replace 
it with an identical card. Anything else and you still would not be able to 
recover your disks. At least with LVM2 you're not restricted to any 
particular hardware make, model, or hardware configuration.

	For what it's worth, I use LVM2 on every new install, desktop or server. 
Since you were speaking only of RAID0, you wouldn't need to do a RAID (md) 
install. As I understand it, LVM2 can handle striping, itself.

Cheers!

cmr

> Vu


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