[Clug-tech] LVM Sanity Check

[Jon]

Hey Sam,

I won't stone you. In fact, I totally agree with you. It's just that I'm 
working with Millennium Falcon parts here.

It seems that I might not have to go the USB route after all, but I'm 
not sure yet. It seems that VMWare's estimation of disk usage is pretty 
out there and I might have more than I think.

For example - when I am inside one of my VMs it showed 650GB of files in 
one particular partition. However, when I do a du on the host machine in 
the directory that holds this VM, it shows that the VM is taking 950GB. 
This VM is a bare bones Ubuntu server install with the aforementioned 
data. I know that there's no chance the Ubuntu OS is taking up the 300GB 
difference.

I'm deleting the 650GB of data now in preparation for shrinking the VM. 
It may well turn out that I get almost a TB back from this little 
exercise in which case I can probably squeak by without the USB drive.

On another note, even if I do need extra space I ran across a 250GB 
drive sitting around doing nothing today. I'm pretty sure this machine 
has at least one empty SATA slot in which case I'll just add this drive 
to the LVM rather than the USB drive.

Once I've actually done this I'll post what I did. Might make good 
academic reading, anyhow :)

Jon

bogi wrote:
> Hi, now some may stone me for saying, but i would not go a usb drive solution. 
> USB is far too temporary, and in many cases unstable to build a filesystem to 
> store a TB of data, even temporarily. I would connect the extra drives onto 
> the sata or the ide channels and extend the filesystem that way. It is your 
> only backup that you can simply restore. I would advice against the USB drive 
> solution. And USB is slower then the others in data transfer, looking at the 
> amount you are talking about, it could take a few days before the copy 
> procedure finishes, you need a stable system.
> Cheers 
> Szemir
> 
> On April 19, 2007 14:54, Jon wrote:
>> Hi All,
>>
>> The next step in my never-ending NAS saga is to copy the data off it
>> before exchanging it. Thanks largely to this group, I have some good
>> ideas how to copy the hardlinked data over to another file system. My
>> challenge now is to construct a file system big enough (1TB).
>>
>> I have 600GB free on an Ubuntu 6.06 LTS server here and I'm thinking
>> that I can make up the rest with two UBS drives. The server is already
>> LVMd so it's my suspicion that I can simply add the two USB drives to it
>> and copy away. This is just a temporary expansion of the LVM in order to
>> facilitate the move. The USB drives won't be staying.If it matters, the
>> server is LVM'd on top of a RAID5.
>>
>> I've been reading Falko's LVM How To on howtoforge.com
>> (http://howtoforge.com/linux_lvm_p5) - most specifically Page 5 where he
>> details how to add a drive to an LVM.
>>
>> My current LVM is 1.09TB as reported by lvscan and with a 300GB USB
>> drive I can get 1.30TB (proven through experimentation).
>>
>> Before I embark upon this craziness, however, I'd like to do a bit of a
>> sanity check. I intend to do something to the effect of (my drive will
>> probably be /dev/sde1)
>>
>> 1. pvcreate /dev/sde1
>> 2. vgextend myVG /dev/sde1
>> 3. umount /dev/myVG
>> 4. lvextend -L1.30T /dev/myVG/myLG
>> 5. mount /dev/myVG/myLG /data
>>
>> Obviously that's only 900GB so I'll have to repeat with another drive to
>> get the full space I need.
>>
>> My questions are:
>>
>> 1. Can USB drives be used (temporarily) as physical volumes in a VM?
>> 2. Does this look sane otherwise?
>>
>> Any and all tips are appreciated.
>>
>> Thanks!
>>
>> Jon
>>
>>
>>
>>
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