Creating Thin-provisioned LVs on SimplStor

Creating thin-provisioned volumes using Logical Volume Manager (LVM) provides a means of managing overall storage space as well as providing for the use of Snapper. Snapper provides snapshot functionality similar to that available on NetApp's Ontap storage operating system.

Add a New Disk Group:

If you have a large group of disks that you want to make into a new Disk Group, use the MegaRAID Storage Manager to create the desired Virtual Disk (VD). The Storage Manage GUI has a wizard that will step you through the process. Shortly after creating a new VD, the RAID controller will start an "initialization scan". This is actually just a simple block level integrity scan and does not alter any data on the disks. You can continue to use the VD while this scan is taking place.

If you created a new Disk Group you should now have a new Virtual Disk (VD) ready to be used by Linux. This should be visible as a new SCSI device of the appropriate size. Determine the device path of the new VD with sfdisk:

 # sfdisk -l

Now initialize the new device as an LVM Physical Volume (PV) with pvcreate (assuming we've added /dev/sde in this example):

# pvcreate /dev/sde

This new PV can be added to an existing or new LVM Volume Group (VG).

# vgextend vg1 /dev/sde

or

# vgcreate vg2 /dev/sde

The new space in the VG can be used to create a new thin-provisioned LVM Logical Volume (LV). The first step is to create a provisioning "pool" in the volume group. 

# lvcreate -L50T --thinpool datapool1 vg1

Next we create a thin-provisioned Logical Volume using the storage pool just created, then format this as an XFS file system and mount the file system. For example:

# lvcreate -L25T --thin -n data2 vg1/datapool1
# mkfs.xfs -i size=512 /dev/vg1/data2
# mount /dev/mapper/vg1_data2 /data2

Setting up Snapper

Snapper is an open source utility created by SUSE Linux and offered on many other Linux variants, including Enterprise Linux 7. After initializing Snapper on a thin-provisioned mountedd XFS file system, a variety of commands can be used to configure, schedule, mount and unmount snapshots.

Create the initial Snapper configuration

# snapper -c data2 create-config --fstype "lvm(xfs)" /data2

This will create a configuration entry in /etc/snapper/configs/. You can view and modify this configuration using either the 'snapper get-config' command and the 'snapper set-config' commands

# snapper -c data2 get-config
# snapper -c data2 set-config TIMELINE_LIMIT_HOURLY=12
# snapper -c data2 set-config TIMELINE_LIMIT_DAILY=14

Using snapshots

Here are some of the commands to create, list, compare, mount, unmount and delete snapshots

# snapper -c data2 create --type [pre|post|single]
# snapper -c data2 list
# snapper -c data2 status <firstnum>..<lastnum>
# snapper -c data2 mount <number>
# snapper -c data2 umount <number>
# snapper -c data2 delete <number>