If you can view the snapshots from the OS through fdisk -l(which means
they have been mapped to the host properly) then you can as well mount
them to retrieve data.

Is that the question ? Maybe I haven't understood properly.

-----Original Message-----
From: Scott R. Ehrlich [mailto:sc...@mit.edu] 
Sent: Thursday, December 11, 2008 12:37 AM
To: Iyer, Shyam
Cc: open-iscsi@googlegroups.com; linux-poweredge-Lists
Subject: RE: Help with Dell MD3000i, snapshots, and CentOS 5.2

Hi Shyam:

Yes, I've seen that pdf before.   Unfortunately, none of the
I have, nor none of exploration of mdsm, has led me to the answers,
hence my emails to this list.  It is all high-level.

I'm aiming for specifics.  I think once I have answers to the simple
request of how to create a snapshot of a live filesystem under
RedHat/CentOS using the snapshot feature, where the snapshot lives, and
how to access it, I'll then be able to place this device into
Lack of these answers is what is holding back use of this device.



On Thu, 11 Dec 2008, shyam_i...@dell.com wrote:

> Scott wrote:
>> I have a Dell MD3000i connected to a PowerEdge 2950 server running
> out-of-box CentOS 5.2 64-bit, unpatched, on an isolated test LAN.
>> I also purchased the snapshot premium feature.
>> Using the included Modular Disk Storage Manager, I successfully
> activated the premium feature, and manually created two RAID 5 arrays 
> +
> 1 hot spare.
>> By manually, I used MDSM instead of letting the software 
>> automatically
> allocate all disk space for me.  I deliberately selected manual and 
> allocated 50 GB minus the 550 GB of each of the two RAID 5s, thus RAID

> 5
>> #1 (call it fs1) = 550 GB - 50 GB for snapshots = 500 GB for RAID 5,
> 50 GB for snapshots; same for RAID 5 #2 (call it fs2).
>> Log back in to the md3000i via iscsiadm, perform an fdisk -l, and see
> 4 x 500 GB partitions (2 x 500 GB per RAID 5, 2 x 500 GB per
>> A few questions now -
>> - how do I actually create snapshots of fs1 and fs2?   What specific
> command do I use, and what specific options do I give it?  No 
> documentation I have, including the index of CLI commands, gives a 
> good enough idea/hint of this
>> - how do I access/view the location where the snapshots are
> stored/created (to retrieve data if needed)
>> - under MDSM's disk groups and virtual disks, it shows 500 GB for 
>> fs1,
> 500
>> GB for snapshot, and 50 GB for snapshot-repo.   What/where is the 50
> GB?
>> Fdisk -l doesn't show it.
> I guess this has been asked before in the linux-poweredge mailing list

> here 
> http://lists.us.dell.com/pipermail/linux-poweredge/2008-July/036871.ht
> ml
> .
> You might also look at documentation here at 
> http://www.dell.com/downloads/global/products/pvaul/en/data_protect_md
> 30
> 00i.pdf.
> Shyam Iyer
> Dell Linux Engineering

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