[linux-lvm] If one disk fails i loose everything?
Old Fart
rascal.jumper-747 at cox.net
Fri Dec 9 18:34:01 UTC 2005
gwood at dragonhold.org wrote:
> In the answers below I've taken 'one linear volume group' to actually mean
> 'one linear volume using all the space in the volume group'. If this is
> not what you meant, can you please describe your setup?
>
>
>> 1. If one hard disk fails (hardware) do I loose all the data stored on
>> the VG?
>>
> I'm not sure where you searched, but the answer to this is a fundamental
> characteristic of RAID0 - there is no redundancy. If you have a concat
> (rather than a stripe), then you /might/ be able to salvage /some/ data -
> but the chances are pretty slim that you'll get anything sane back out of
> it, and you're going to have to do some relatively low level stuff to do
> even that I would have thought.
>
>
>> 2. Can I add a new hard disk in the VG without having to format it
>> before? (I mean if it is full of data can I just add it?)
>>
> Not easily using LVM on linux, no. If it already has partitions on it,
> then the layout of the data on the drive is incorrect for LVM. There may
> be tools out there to overlay the required metadata, but the underlying
> partitions will have to reduce in size, so this would require the
> filesystems to support being shrunk.
>
>
>> 3. In case of failure can I recover the data from a single disk on
>> another box?
>>
> What sort of failure? Any VG that has enough drives to provide you with a
> working volume group/volume can be imported to another machine and read.
> So if you have 3 volumes over the VG, and only one of them doesn't have a
> complete set of blocks on it - the other 2 can be salvaged. In the case
> of the arrangement you're talking about, no.
>
> If you need to be able to recover the data, then a simple linear volume
> (with no redundancy) is not a good idea.
>
> (In answer to the subject line, 'with the arrangement you're talking
> about' - YES')
>
> _______________________________________________
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> linux-lvm at redhat.com
> https://www.redhat.com/mailman/listinfo/linux-lvm
> read the LVM HOW-TO at http://tldp.org/HOWTO/LVM-HOWTO/
>
>
Good discussion....the need to protect data under various contingencies
is why I use raid5 sets as the PVs. You can lose up to two and keep
your data, hot add, have spares, etc.
--
Regards,
Old Fart
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