Flexible Storage Management

The Exoscale Flexible Storage Template aims to empower users so they can manage their instance’s disk/storage as they deem fit. The storage template provides:

  • A minimalistic Debian-based template with no extraneous components and only what is required to get you started (namely, cloud-init and sudo)

  • A built-from-scratch template using the Debian netinst installation media and the ssh-server installation scenario (AKA tasksel)

  • Uses UEFI boot mode and a GPT partition table (as opposed to Debian’s stock cloud image) to enable support for disk images larger than 2 TB (along Exoscale Storage Optimized Instances)

  • Uses LVM logical partitioning (as opposed to Debian’s stock cloud image) to allow you to manage partitions and file systems as you deem fit

The flexible storage template is based on - but deviates minimally from - Debian’s stock installation configuration, so it is easy to embrace for users accustomed to Debian or Ubuntu.

Deploying a Flexible Storage Instance

The flexible storage template is based on - but deviates minimally from - Debian’s stock installation configuration, so it is easy to embrace for users accustomed to Debian or Ubuntu.

exo compute instance create storage \
  --zone <desired-zone> \
  --template 'Exoscale Flexible Storage 10' \
  --disk-size 50 \
  --ssh-key <your-SSH-keypair>

Log In

After the instance is deployed, log into it via SSH with the CLI:

exo compute instance ssh storage
# [output]
debian@storage:~$

Then use sudo to obtain administrative privileges:

debian@storage:~$ sudo -i
# [output]
root@storage:~#

(For the sake of readability, we will hide the root@storage:...# command prompt in further shell commands examples.)

Flexible Storage Management

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Create Flexible Storage Instance

Stashed changes

Creating a flexible storage instance is similar to creating any other Exoscale Compute instance. Here is an example with the CLI:

exo compute instance create storage \
  --zone <desired-zone> \
  --template 'Exoscale Flexible Storage 10' \
  --disk-size 50 \
  --ssh-key <your-SSH-keypair>

Log In via SSH

After the instance is deployed, log into it via SSH with the CLI:

exo compute instance ssh storage
# [output]
debian@storage:~$

Then use sudo to obtain administrative privileges:

debian@storage:~$ sudo -i
# [output]
root@storage:~#

NOTE
For readability, further shell commands will omit the root@storage:...# command prompt.

Default Partition Layout

Thanks to the Linux Logical Volume Manager (LVM), as well as following the Linux Filesystem Hierarchy Standard (FHS) and general best practices, the flexible storage template’s initial partitioning separates a few systems. These are ext4-formatted partitions, namely / (root), /var, /tmp (as well as /boot and /boot/efi):

lsblk

List block devices (disks/partitions):

# [output]
NAME                MAJ:MIN RM  SIZE RO TYPE MOUNTPOINT
vda                 254:0    0   50G  0 disk
|-vda1              254:1    0  511M  0 part /boot/efi
|-vda2              254:2    0  512M  0 part /boot
`-vda3              254:3    0    9G  0 part
  |-vg.flex-lv.root 253:0    0    5G  0 lvm  /

  |-vg.flex-lv.var  253:1    0    2G  0 lvm  /var
  `-vg.flex-lv.tmp  253:2    0    1G  0 lvm  /tmp

NOTE
The 50G disk (vda) space not being entirely used by underlying partitions (vda<N>).

As opposed to most other templates, partition sizes will not automatically grow after an instance’s disk is resized. You can create or resize partitions according to your requirements.

Storage Management Operations

Further, as an example, we will demonstrate both:

  • how to create a new /data partition with the xfs filesystem
  • how to resize the /var partition

Create New Logical Volume

You can create as many partitions or file systems as you need. Here is an example with a xfs-formatted /data partition - install XFS utilities:

apt-get install xfsprogs

Create the LVM Logical Volume (LV):

lvcreate -n lv.data -L 20G vg.flex

Output:

Logical volume "lv.data" created.

Show the LVM Logical Volume (LV) details:

lvdisplay /dev/mapper/vg.flex-lv.data

Output (partial):

  --- Logical volume ---
  LV Path                /dev/vg.flex/lv.data
  LV Name                lv.data
  VG Name                vg.flex
  LV Status              available
  LV Size                20.00 GiB

Create the filesystem:

$ mkfs.xfs -L DATA /dev/mapper/vg.flex-lv.data

Output (partial):

meta-data=/dev/mapper/vg.flex-lv.data isize=512    agcount=4, agsize=1310720 blks

Create the filesystem mountpoint:

mkdir -p /data

Mount the filesystem:

$ mount /dev/mapper/vg.flex-lv.data /data

Show the filesystem capacity/usage:

df -h /data

Output:

Filesystem                   Size  Used Avail Use% Mounted on
/dev/mapper/vg.flex-lv.data   20G   53M   20G   1% /data

You may want to add to /etc/fstab to allow automatic mounting at boot time:

grep /data /etc/fstab

Output:

/dev/mapper/vg.flex-lv.data /data xfs defaults 0 2

Resize the Physical Volume

The first step is to grow the /dev/vda3 partition, corresponding to the LVM Physical Volume (PV) - show LVM Volume Groups (VGs)

vgs

Output:

  VG      #PV #LV #SN Attr   VSize   VFree
  vg.flex   1   3   0 wz--n- <9.00g  1.00g

Grow the LVM-backing disk partition:

growpart /dev/vda 3

Output:

CHANGED: partition=3 start=2097152 old: size=18872320 end=20969472 new: size=102760415,end=104857567

Grow the LVM Physical Volume (PV):

pvresize /dev/vda3

Output:

  Physical volume "/dev/vda3" changed
  1 physical volume(s) resized or updated / 0 physical volume(s) not resized

Show LVM Volume Groups (VGs):

$ vgs

Output:

  VG      #PV #LV #SN Attr   VSize   VFree
  vg.flex   1   3   0 wz--n- <49.00g 41.00g

NOTE
The increase of VFree space in the LVM Volume Group (VG).

Resize a Logical Volume

To resize (or extend) an existing LVM Logical Volume (LV) and partition (with /var as an example) - grow the LVM Logical Volume (LV):

lvresize -L +10G /dev/mapper/vg.flex-lv.var

Output:

  Size of logical volume vg.flex/lv.var changed from <2.00 GiB (511 extents) to <12.00 GiB (3071 extents).
  Logical volume vg.flex/lv.var successfully resized.

Grow the filesystem:

resize2fs /dev/mapper/vg.flex-lv.var

Output:

resize2fs 1.44.5 (15-Dec-2018)
Filesystem at /dev/mapper/vg.flex-lv.var is mounted on /var; on-line resizing required
old_desc_blocks = 1, new_desc_blocks = 2
The filesystem on /dev/mapper/vg.flex-lv.var is now 3144704 (4k) blocks long.

Show the filesystem capacity/usage:

df -h /var

Output:

Filesystem                  Size  Used Avail Use% Mounted on
/dev/mapper/vg.flex-lv.var   12G  217M   12G   2% /var