Re: Moving from RAID 0 to LVM RAID?

["Ben Holland" <user=122@nabble.blu.org>]

 Ahhh I am not sure now, it very well could have been psudo raid but there 
was a built in raid controller that once the bios booted up you could 
configure your settings. It is quite possible that this was in fact done 
with bios driven stuff which I don't think I would ever wish to use. I do 
know though that every time I've had a SCSI controller it's had RAID built 
in to the hardware, SATA most of the comps didn't but they were also really 
low end and the newer ones said they had some form of RAID, the few that had 
>4 drives generally came with raid 5, in this day and age I wouldn't buy a 
computer that could take >=4 drives without getting hardware raid 5 built in 
to hardware, but that may mean i'm a picky bastard, which I freely admit to 
being. Just a quick question, how do you know if what you are getting has 
real raid vs psudo raid if they both look the same? ~Ben 

On Fri, Mar 7, 2008 at 9:56 AM, Jarod Wilson <[hidden email]> wrote: 

> On Thu, 2008-03-06 at 23:49 -0500, Ben Holland wrote: 
> > >> this is bad and in fact your LVM controller may really 
> > >> hate you 
> > 
> > >Um... There is no such thing as an LVM controller. Its all done in 
> > >software by the kernel. 
> > 
> > Recovery from a broken disk, I would say depending on the drive 
> condition 
> > but over all when i've seen drives die they die hard, some of the data 
> is 
> > recoverable I'm sure but not all. 
> 
> I believe both Tom and I were referring to recovery of data from a 
> logical volume that spanned multiple physical disks. i.e., LVM is more 
> like JBOD than RAID, where files are usually constrained to one disk or 
> another, so files on the non-dead drives are completely intact and 
> easily recoverable. 
> 
> > And the controller I was talking about is 
> > the kernel module, obviously it's not in hardware. Perhaps I'm using the 
> > wrong word, I've always referred to the thing that governs the LVM's as 
> the 
> > lvm controller. 
> 
> Ah, okay. I think scsi controller -> hardware, raid controller -> 
> hardware, sata controller -> hardware, etc., so an 'lvm controller' 
> logically follows as a piece of hardware too. 
> 
> > LVM's  I would say are kinda neat, but to be honest I still 
> > haven't seen a case where they were needed. 
> 
> Me neither. They annoy me, and I don't use 'em most of the time. 
> 
> > >I'd wager more like 50-50. I've seen plenty of 2U boxes that have 4 to 
> 6 
> > >drive bays and don't come with any RAID controller at all, let alone 
> one 
> > >capable of RAID 5. 
> > 
> > I'm very surprised by this. Every low end rack comp i've seen that 
> wasn't 
> > more then 3 years old has come with some form of raid, to the point 
> where I 
> > can even get hardware raid on MB's for personal home comps. 
> 
> You sure that's actually hardware RAID you're talking about, and not the 
> crappy bios-driven pseudo-raid, which is really just glorified software 
> RAID (with all the drawbacks and none of the benefits of linux kernel 
> software RAID)? 
> 
> > There were a 
> > bunch i've worked with that were true POS in every sense of the word, 
> but 
> > they were EOL and their replacements had raid on board. Every single 4-6 
> HDD 
> > comp i've seen I think i've seen a built in raid controller capable of 
> > handling 5. If not then I highly recommend getting boxes that do in fact 
> > have hardware raid, if you can't then use software. 
> 
> Lots of low-end rack hardware from the likes of both Dell and HP (the 
> bulk of what we have in our lab) come with nothing but SATA controllers 
> that only do bios pseudo-raid, unless you opt for upgrades. 
> 
> 
> -- 
> Jarod Wilson 
> [hidden email] 
> 
> 
> -- 
> This message has been scanned for viruses and 
> dangerous content by MailScanner, and is 
> believed to be clean. 
> 
> _______________________________________________ 
> Discuss mailing list 
> [hidden email] 
> http://lists.blu.org/mailman/listinfo/discuss
>