Registered: Jul 2001
Location: Norfolk, VA
Posts: 4701

From what I've been reading, CENTOS comes running Raid0, meaning that if I have several physical disks, then I can span one volume across all the disks.

I was intending to use this feature to add storage capacity to my fileserver by buying some big hard drives over the next year. However, from what I've been reading, I need to blow away the existing volume in order to add new drives to it.

So, does anyone know if I can use growfs to just add a new drive to a volume? Can I just resize the volume to include new physical disks?

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Registered: Dec 2002
Location:
Posts: 3063

is it using LVM by default? If so, you may be able to add another physical disk to your current logical volume.

You don't need to stripe if all you want is additional capacity. Striping improves performance, and for your home system, is probably overkill. It also causes your system to become completely useless if you lose a single disk. Better to lose half your data than all, no?

http://en.wikipedia.org/wiki/Logica...ger_%28Linux%29
http://en.wikipedia.org/wiki/Redund...nt_disks#RAID_0

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Registered: Aug 2000
Location:
Posts: 1731

Now this is right up my ally...

please post the output of: cat /proc/mdstat

and: lvdisplay

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Registered: Jul 2001
Location: Norfolk, VA
Posts: 4701

[squee@localhost ~]# cat /proc/mdstat
Personalities :
unused devices: <none>

...

[squee@localhost ~]# lvdisplay
--- Logical volume ---
LV Name /dev/VolGroup00/LogVol00
VG Name VolGroup00
LV UUID rWQEEv-8Gmk-HA4K-hJxi-Pmlh-JsLi-5KoXFX
LV Write Access read/write
LV Status available
# open 1
LV Size 73.88 GB
Current LE 2364
Segments 1
Allocation inherit
Read ahead sectors 0
Block device 253:0

--- Logical volume ---
LV Name /dev/VolGroup00/LogVol01
VG Name VolGroup00
LV UUID E6cVRk-Jx7m-mlkz-mlt5-130m-dkXI-ZFehOk
LV Write Access read/write
LV Status available
# open 1
LV Size 512.00 MB
Current LE 16
Segments 1
Allocation inherit
Read ahead sectors 0
Block device 253:1

I hope you feel like explaining to me what this all means...

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Registered: Aug 2000
Location:
Posts: 1731

no mdstat = no RAID enabled.

lvdisplay = display status of your logical volumes. You have 2.

/dev/VolGroup00 = your physical volume (the actual raw space). More than one disk may make up a Volume Group. It is only the amount of physcial data that may be logically divided.

LogVol00 and LogVol01 are the logical volumes or storage pools in the physical volume.

*** NOTE: Essentially, a logivcal volume if you havnet already figured it out is a storage pool of space that can grow or shrink on command, may span over several disks which you can add or remove as needed on the fly, without fucking up or with partitions.

Ok, you have two volume groups (as previously mentioned), which are part of one physical storage pool VolGroup00. This is the standard default setup of Fedora or Cent, etc. The 512 MB volume (LogVol01) is your swap space, and LogVol00 is your os, and storage space.

Say I wanted to give your swap space 1 gig. I would first need to get that physical space available. I would do this by taking it away from the storage pool (logvol00):
#lvreduce -L 512M VolGroup00/LogVol00

lvreduce reduces a logical volumegroup size, -L specifices I want to be stupid and enter the number in terms an idiot could understand (thus the: 512M), and then of course the physical volume, and the logical volume group.

Now that this done, you now have 512M Physcial of physical storage available to add to your swap. This doesnt mean you can just go: lvextend -L 512M VolGroup00/LogVol01. This will not do anything. Because there is alread 512M there, you have to specify that you are making that volume 1024M, thus:

#lvextend -L 1024M VolGroup00/LogVol01

Type lvdisplay and WALLA, you have extended your swap space to be one gig in size.
My fingers are tired, if you need to know how to add raw space of a new disk to a physical volume, ask, and ill explain in about a week.

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