At Wednesday, 15 December 2004, you wrote:
>On Thu, 16 Dec 2004, Joao Clemente wrote:
>
>> Ok, Alvin, as far as I understand when you said at the top "for
sanity
>> ... i always fdisk the new disk to be the same as the remaining
disk"
>> you mean limiting it's size, as you say here at last few lines,
right?
>
>i manually partition the new disk, because i do not trust that
>the sw raid mirroring will partition the right way
>
>> My doubt is: If you DONT do this (and, following my steps, you CANT
>> fdisk unless you power the machine first :-) what will happen then?
>
>you cannot fdisk once /dev/mdxxx is created
>
>you create the sw raid by:
> fdisk /dev/hda ...
> fdisk /dev/hdc ...
>
> ( if you do NOT partition it ... i think sw raid uses
> ( the whole disk as 1 giant partiton .. i always partition it
>
> mdadd /dev/md0 /dev/hda1 /dev/hdc1
> mdadd /dev/md1 /dev/hda2 /dev/hdc2
> ...
>
> mke2fs -j /dev/md0
> mke2fs -j /dev/md1
> ...
>
> mount /dev/md0 /
> mount /dev/md1 /home
Oh, I think I see what I am doing incorrectly, I still have mounted
/dev/hda1 /home ... not /dev/md0 /home
Also, my raidtab is:
development:/etc# cat raidtab
raiddev /dev/md0
raid-level 1
nr-raid-disks 2
nr-spare-disks 0
chunk-size 4
persistent-superblock 1
device /dev/hda
raid-disk 0
device /dev/hdc
raid-disk 1
> ...
>
> fix /etc/mtab or wherever the equivalent file is saved
>
>> Supose you have your disks with 3 partitions each, {hd?1, hd?2,
hda?3}
>> from wich you have your 3 software raid partitions {md0, md1, md2}.
>
>good
>
>> One disk fails. You put a new one. New as "out-of-the-shop", no
>> partitions, no filesystem. What happens? Will the partitions be
>> generated?
>
>yes ... if you trust the system to do it for you
>
>> Or you need do setup {hdx1, hdx2, hdx3} on the new disk,
>> before software raid resyncs the disks?
>
>i prefer to manually fdisk the new disk so that i dont count
>on the sw code to do it right or wrong
>
>> Or this is not the way to do it?
>
>trail and error ...
>
>i've never had a problem when i fdisk it manually first
>and it also tells me i can write the disk, at least partition it
>
>> From what I remember reading, HW RAID handles "disks", SW RAID
handles
>> "partitions".
>
>i think you can make /dev/hda1 and /dev/hdc1 as one "whole disk"
>
>even "hw raid" will have at least one partition
>
>if you use oracle .. they will use raw disks .. no partitions
>
>> If you replace a disk in a HW RAID, the new disk will be
>> copied and be equal to the older ones.
>
>not necessarily...
>
>but than again, most people do not mix and match different sized
>disks when replacing the dead one
>
>and in sw raid .. you can have the dead 40GB disks replaced by
>a 300GB disks and everythign will still work properly
> and have a spare (unused) 260GB on the new disk
>
>> Mapping this to SW RAID makes the
>> sentence like this: "If you replace a PARTITION in a SW RAID,
the new
>> PARTITION will be copied and be equal to the older ones".
>
>for the mirrored and used portion of the raid ..
>
>> So what
>> happens if the disk has no partitions?
>
>sw raid will partition the new disk for you
>and format it and merge it into the raid array and sync
>the data onto the new disk
>
>c ya
>alvin
>
>--
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