bergman on 1 Sep 2005 01:39:18 -0000

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Re: [PLUG] hard disk partitioning

In the message dated: Wed, 31 Aug 2005 20:42:38 EDT,
The pithy ruminations from "Rodney Oliver" on 
<RE: [PLUG] hard disk partitioning> were:
=> Thanks for the advice,  especially about the /boot directory.  This is my

Well, depending on the application, I'd strongly recommend that you do mirror 
(RAID1) /boot and swap. I'd never put them on a RAID0 or RAID>1 device.

=> first attempt at LVM volumes on a raid array and I'm testing it out on an
=> old Intel workstation in my office. So, I'll just use software raid for now.
=> Here is another question:
=> The workstation I'm attempting this on has two hard drives hda and hdb.  hda
=> is an 80gb drive and hdb is a 115gb drive.  I created a 2gb /boot partition
=> on hda1, then used the rest of the free space as the RAID partition.  On hdb
=> I used the entire disk as my second RAID partition.  I then created a RAID 1

A RAID 1 partition is mirrored, giving you a fully redundant copy of the data 
on both drives, but the effective usable space will be the size of 
the smaller drive (you can't mirror 115GB onto a 78GB partition).

=> md0 from of both those drives.  Here is where I get lost.  When I create the
=> RAID1 array md0 it only shows 77564mb of space available in the md0 array.
=> I'm positive I included both drives in the array. Shouldn't the space be
=> more like (77567 + 114471)192035mb? Anyone have any thoughts?  What am I
=> missing

Um, you're missing about 27GB. :)

>From your description, it sounds like you intended to set up a RAID0 
metadevice, which is a concatenation (or stripe) of the data across multiple 
drives. That would give you ~195GB of usable space, but with no redundancy. If 
either drive goes bad, effectively all the data on _both_ drives is lost.


=> Thanks for your help!
=> -----Original Message-----
=> From:
=> [] On Behalf Of Jason
=> Sent: Tuesday, August 30, 2005 8:04 AM
=> To: Philadelphia Linux User's Group Discussion List
=> Subject: Re: [PLUG] hard disk partitioning
=> On 8/30/05, Rodney Oliver <> wrote:
=> > Hi all,
=> > 
=> > Is it possible to create a RAID 1 array using two drives then LVM those
=> > drives?  If so where can I find some good documentation with example
=> > partitioning schemes?
=> Assuming you mean using Liinux software raid, sure, you can do that.
=> When you create your LVM volume, instead of using a physical
=> partition, like say /dev/hda2, you'll just reference an md device,
=> like say /dev/md0.
=> While it may be technically possible to raid your /boot, I'd recommend
=> you save the headaches and not bother with it.  Same for swap, don't
=> use a raid for swap.
=> If you're really serious about building it out "the right way", go
=> with a single drive that will house /boot and swap space, smallish,
=> like 2-4 gb.  Add to that a hardware raid adapter and the drives.  You
=> can use LVM on the RAID volume.  Most distros seem to just make 3
=> partitions these days, /boot, / and swap.  There are plenty of reasons
=> to splinter the filesystem further, such as keeping /var and / apart
=> from /home so that user activity won't crash the box if they run their
=> filesystem out of space.
=> It really depends on how the box is being used.  The best advice I
=> could give about this?  Think.  Think some more.  When you're done -
=> think again.  You'll be glad you planned it all out down the line.
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