Brandon Beattie wrote: > This was my example of the >pitfall that people think they can use LVM and change space around, for >whatever reason, whenever they want. If you use XFS, JFS, or Reiser4 >then you can only swap disks around and add space -- you can never shrink >the filesystem and there's many uses that this feature is important. > That's true - and a valid observation I suppose it depends whether you are a fiddler or not. My big filesystem is dedicated to Myth. If a disk dies then it needs replacing. As always it depends what you require in order to decide upon a solution.
>If you decided to just pull the drive because you need it in another >system, you can not do that with a file system that does not support >shrinking. I'm sure very, very few people know this and those people >probably had thought they could, because it's LVM, which can grow and >shrink as it wants, and people are given a false impression that the >file system does not effect this. > > Not if you read the Howto or any other LVM docs that mention shrinking... http://www.tldp.org/HOWTO/LVM-HOWTO/reducelv.html >For me, I see a disk is starting to reallocate blocks so I know it will >begin failing in weeks to months > <insert>or seconds.</insert> > and if (for example) I had used >ReiserFS instead of XFS I could have > <insert>tried to..</insert> >shrunk the filesystem and LVM and >taken the disk out right then. Having chosen XFS I can not do this. > > correct. >>You have an excellent point regarding that fact that you can not shrink >>certain file systems. IMHO trying to use LVM to provide a solution for >>handling failed drives or as a method of replacing failed drives is not >>the right tool for that job. >> >> >My choice for LVM was never to avoid failed disks, it was chosen to >isolate failure to partial loss for things I only minorly care about but >almost completely for convenience and functionality. The only way >to avoid complete loss is make it less likely, and even raid5 complete >loss is something I've seen > OK. But in your original message (see "My terrible options, 1,2 & 3") seemed to be saying: "If I'd used LVM with a filesystem that can shrink then I would have had _some_ protection against disk failure" And that's, IMHO, a bad message. I know you understand what you mean in the case of a SMART alert - but frankly, for most people, most of the time, using non-redundant LVM without raid *increases* your chance of data loss by a factor roughly equal to the number of disks in the volume(1). So any suggestion that the filesystem choice assists in the case of disk failure is probably a disservice to most people who are of an experience level where they are reading this mailing list for advice. David (1) For other readers, yes, if you have a vanilla 5 disk LVM you are about 5 times _more_ likely to suffer a massive loss of your data. Brandon, I know you understand this :) _______________________________________________ mythtv-users mailing list [email protected] http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
