Re: LVM over RAID
On Fri, Jul 23, 2004 at 01:37:16PM +0100, Pete Clarke wrote:
} Hi gurus...
} I have a question regarding LVM and RAID.
} I have a 324gb and 350gb RAID enclosure, the 324gb consists of 9 x 36gb
} discs, and the other is 7 x 50gb discs.
} This space is destined for a file server, and usually I would just use
} appropriate RAID level to define the volumes etc.
Are you using hardware RAID or software RAID? It sounds like you intend
to use software RAID. It doesn't really change much, though.
} However, after being caught out with needing more space in the past I
} decided to go the LVM route, what I need to know now is how best to go about
} it...Do I:
} Just treat each drive as a seperate device (i.e JBOD) and create a PV for
} each disc and use software striping where necessary, or define each array as
} one big RAID 0 (backup is taken care of) and create lots of little
} partitions to use as PV's?
If you don't actually want RAID functionality, you can use LVM to glue
all the disks together into one big virtual disk. That sounds like your
goal. Mind you, I'm a big fan of actually using RAID if I have enough
disks lying around to do it. I have an 8 x 18GB RAID5 myself.
} I guess the second route would be the best bet, as it would use the benefit
} of hardware RAID 0 with smaller partitions. But would this cause issues by
} having potentially *lots* of partitions spread over the disc (the howto
} advises against using the partitions for PV's but rather to use whole
} devices (discs /dev/sdxx etc.)).
That's largely meaningless. Hardware RAID makes the entire group of
disks look like a single device.
} I am basically looking for the solution that provides the best balance
} between performance (speed is really an issue) and flexibility.
Are you optimizing for write speed, read speed, or a balance? Is
redundancy not worth any speed reduction?
} I have checked Google and the various howto's but they don't really
} touch on this scenario...