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Re: [linux-lvm] Drive gone bad, now what?



John Stoffel wrote:

Gert> I didn't expect lvm to restore the missing data, I guessed it
Gert> would just let me access the rest of the data.

At this point, you have to think, how can my filesystem cope with the
loss of a 60gb chunk of data in the middle (start or end even) of the
300+ gb of data? There's all sorts of meta-data and true data which
is now gone, and re-building the filesystem into a consistent state is
really impossible.


Hmm, and so I think LVM still needs a warning label :-)

I wonder why LVM doesn't work the other way around:
Create filesystems on several disks and then concatenate these to the outside as one large filesystem. This way if one drive goes bad you can always individually mount the drives and use the data.


If you are looking for a large/cheap/reliable bunch of storage,
instead of mirroring, you might want to think about RAID5 instead.

No, what we're looking for is an 'expandable as needed' filesystem and this is what LVM pretends to be.
Our server acts as a NAS and when it gets full you add more drives or exchange them for (a set of) larger ones.
To the user it still is the same network share, just bigger.


your case, you had a mix of disks, so what you could do is build a
pair of RAID5 arrays using disks of the same size for each array
(minimum of three disks each of course) and then stripe the filesystem
across both arrays.


To add more storage, you need to work on chunks of three disks, but
since 120gb disks are going for around $100 these days, it's not that
expensive.

We will look into raid5, but considering the hardware limitations (number of onboard ports and such), for step by step upgrades the 2 disk mirror option is best I think.

Gert





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