[Klug-general] Raid....

Peter Childs peterachilds at gmail.com
Mon Aug 10 13:42:37 UTC 2009


2009/8/10 Twigathy <twigathy at gmail.com>:
> 2009/8/10 Peter Childs <pchilds at bcs.org>:
>> I'm looking for some up to date documentation on Software RAID its
>> just the Howtos look super ancient and nothing else seams to look
>> right.
>
> A *lot* of the raid guides out there are seriously old and need
> purging from the www. Still using things like /etc/raidconf (Nowadays
> /etc/mdadm.conf).... http://linux-raid.osdl.org/index.php/Main_Page
> has some more up to date info.
>
>> Also fdisk, how do the units work as I've got a 122G disk and a 250G
>> disk which I want partions on of the same size, but the units are
>> different, So wants the best way of specify the sizes, and also
>> ensuring that my raid volume is the size I want even if the partion(s)
>> I'm putting it on currently is bigger due to the layout of the disk.
>
> When partitioning, you can tell fdisk you want a partition '120G' for
> example, and it'll make a 120GB partition for you :)
>

Yes I've got that far its a little silly.

250G disk Units 2048 x 512 = 1048576 (Weston Digital)
122.9G disk Units 16065 x 512 = 8225280 (Maxtor)

So I can have more precision over the size of a partition on the
larger disk than I can on the smaller one... (How does that one work,
Its normally the other way round?)

Now for some reason I requested 120G partitions which gave me 119.99G
or 117178110 Blocks (I think a Block in this case is 1024bytes) but my
Units are oh dear I give up....  anyway the nearest I could get on my
new disk was 117178368 Blocks because the allocation units have
changed...... (I'm using the other 2.9G for kernels and swap (I have 6
disks in this server)) my idea was that if I got 120G disks (that were
smaller from another manufacturer I would still be able to use them.
Its just when I need a new disk the best size to get was 250G due to
the lack of choice now in PATA disks.....

I've got LVM running over 3 RAID1 Partitions giving me 335.24G in
total which is split into 9 logical volumes. Two of the disks have
RAID1 on the 2.9G remaining for /boot (grub can't read LVM but it can
read software raid1) and the other bits is paired to Raid 1 and used
as swap. its faster than using LVM for swap or at least that the
theory....

Peter



More information about the Kent mailing list