[vdr] Re: VDR feature request

[Emil Naepflein <Emil.Naepflein@philosys.de>]

On Wed, 22 Jan 2003 23:34:57 +0100 (CET), <hm@seneca.muc.de> wrote:

> Emil Naepflein <Emil.Naepflein@philosys.de> wrote:
> > It is ok that vdr search the space itself. But the problem with the
> > current strategy is that if you loose one of your partitions you loose
> > most of your recordings. A better strategy for vdr would be to put all
> 
> Maybe I am missing something but what is wrong with setting up a RAID5 if
> you have multiple disks anyway? OK you lose the space for 1 disk but you
> are fault resilient then, 

I am using RAID5 and have lost a partition because two disks died
because of a power failure. After the crash and reactivating one of the
failed disks it wasn't possible to repair the reiserfs. 
Now you can say why haven't you used multiple power supplies and and a
UPS? ;-)

You can invest endless money in fault tolerance and still not be save
against many errors you have not thought of. Therefore it is still
important that the damage that is caused by a fatal error is kept to a
minimum. Regarding disk and filesystem errors my strategy is to use
RAID5 for single-disk errors and multiple partitions with
non-distributed recordings to keep the damage when a filessystem error
happens to a minimum. 

> you have one big virtual disk, you don't need to
> think where to put things etc. 

One big virtual disk is a very bad thing. One error in the filesystem
and all of your recordings may be lost. Please remember that with
several 100 GBs of recordings you have normally no possibility to do a
backup. With multiple partitions you may be able to redistribute the
good recordings to other partitions before doing a risky fsck. And a
further advantage of multiple partitions is that you can add additional
disks to a RAID5 to increase space. I have once started with 3 80 GB
Maxtors and I am now at 7. The upgrade has been done without loosing any
data and without VDR downtime except for plugging in the disks.

And even I have multiple partitions I don't have to think about where to
place files. VDR distributes the files automatically over all partitions
and my tool vdrmigrate automatically collects this files and places them
into one partition where is enough space. VDR could do a bit better when
placing the recordings. 

Emil


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