Actually RAID/volume management is superlimited when not in filesystem...
Posted Jan 8, 2009 1:57 UTC (Thu) by khim
In reply to: Btrfs aims for the mainline
Parent article: Btrfs aims for the mainline
I have to admit that the idea of merging yet another
RAID/volume management implementation, this time within a filesystem, does
not make me very happy.
Actually I can not imagine sane
volume management outside of filesystem. For example here I have 4 HDD
drivers in my system. What I really want?
1. Keep most of the data on just one drive (for movies from my own
2. Keep the rest in RAID-5 form (for movies in games and such: PITA to
reinstall but can be done if needed).
3. Keep my own personal files (1% of total size or so) duplicated 4 times
(on 4 HDDs).
Pretty easy and simple requirements, right? Yet totally unachievable with
usual LVM/filesystem separation. Currently btrfs can not support this mode
of operation too, but potentially - it's doable...
P.S. Actually I got the idea after reading in GFS paper: Users can
specify different replication levels for different parts of the file
namespace. I was dumbfound when read this: this is exactly what
I need from normal filesystem - why it was never actually done? There are
1. It's harder to do for normal filesystem (GFS works with huge chunks and
so fragmentation is not an issue).
2. RAID/volume management is separated from filesystem - there are just not
enough info in filesystem to make in happen!
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