----- Original Message ---- > From: Joost Roeleveld <jo...@antarean.org> > On Thursday 07 April 2011 06:52:26 BRM wrote: > > ----- Original Message ---- > > > > > From: Joost Roeleveld <jo...@antarean.org> > > > > > > On Thursday 07 April 2011 06:20:55 BRM wrote: > > > > ----- Original Message ---- > > > > > > > > > From: Neil Bothwick <n...@digimed.co.uk> > > > > > > > > > > On Thu, 07 Apr 2011 05:22:41 -0500, Dale wrote: > > > > > > I want to do it this way because I don't trust LVM enough > > > > > > to put my > > > > > > > > > > > > OS > > > > > > on. Just my personal opinion on LVM. > > > > > > > > > > This doesn't make sense. Your OS can be reinstalled in an hour > > > > > or two, your photos etc. are irreplaceable. > > > > > > > > Makes perfect sense to me as well. > > > > > > > > Having installed LVM - and then removed it due to issues; namely, > > > > the fact that one of the hard drives died taking out the whole LVM > > > > group, leaving the OS unbootable, and not easily fixable. There > > > > was a thread on that (started by me) a while back (over a year). > > > > > > > > So, perhaps if I had a RAID to underly so I could mirror drives > > > > under LVM > > > > > > > > for recovery I'd move to it again. But otherwise it is just a PITA > > > > waiting > > > > > > > > to happen. > > > > > > > > Ben > > > > > > Unfortunately, any method that spreads a filesystem over multiple disks > > > can be > > > > > > affected if one of those disks dies unless there is some mechanism in > > > place that can handle the loss of a disk. > > > For that, RAID (with the exception of striping, eg. RAID-0) provides > > > that. > > > > > > Just out of curiousity, as I never had the need to look into this, I > > > think that, in theory, it should be possible to recover data from LVs > > > that were not > > > > > > using the failed drive. Is this assumption correct or wrong? > > > > If you have the LV configuration information, then yes. Since I managed to > > find the configuration information, I was able to remove the affected PVs > > from the VG, and get it back up. > > I might still have it running, but I'll back it out on the next rebuild - or > > if I have a drive large enough to do so with in the future. I was wanting > > to use LVM as a bit of a software RAID, but never quite got > > that far in the configuration before it failed. It does do a good job at > > what it's designed for, but I would not trust the OS to it either since the > > LVM configuration is very important to keep around. > > > > If not, good luck as far as I can tell. > > > > Ben > > LVM isn't actually RAID. Not in the sense that one gets redundancy. If you > consider it to be a flexible partitioning method, that can span multiple >disks, > > then yes. > But when spanning multiple disks, it will simply act like JBOD or RAID0. > Neither protects someone from a single disk failure. > > On critical systems, I tend to use: > DISK <-> RAID <-> LVM <-> Filesystem > > The disks are as reliable as Google says they are. They fail or they don't. > RAID protects against single disk-failure > LVM makes the partitioning flexible > Filesystems are picked depending on what I use the partition for >
The attraction to LVM for me was that from what I could tell it supported and implemented a software-RAID so that I could help protect from disk-failure. I never got around to configuring that side of it, but that was my goal. Or are you saying I was misunderstanding and LVM _does not_ contain software-RAID support? Ben
