[linux-lvm] Re: raid 1 on a single disk
Piete.Brooks at cl.cam.ac.uk
Sat Nov 13 13:38:14 UTC 2004
> (please do not top post - fixing. Please take note!)
(what's "top post"ing?)
>> ok so, i also do know, its performance is going to suck !
> No, it'll be fine - merely a couple or more times slower at writing
> large streams.
Actually, over 4 times :-(
He has a 4 way mirror on hdd.
As well as having to send all date over the (same!) IDE bus 4 times,
the disk head keeps having to move between the 4 partitions :-(
> What's silly is that there's no point in doing it
Not true -- there is little point.
It will protect against un-re-vectored block faults.
> you get no protection against the disk disappearing
Indeed -- which is the real use for RAID1 ...
> It's like making 3 sets of spare housekeys, and then putting them all
> in the same keyholder as the original set, and walking around like that.
Which has *some* use if the keys are made of very soft metal and "wear out".
[ His actual problem was that he didn't realise that mkraid is brain dead, and
needs a chunk size in /etc/raidtab, even when it's not used! I showed him how
to use mdadm, and it worked ]
More information about the linux-lvm