In this tutorial, I am going to explain the block storage components in Google Compute Engine. This is an important topic that requires a separate post of its own. Before we start, I would highly recommend you to take a look at the GCE concepts and various options around it.
Persistent disks are non-volatile storage available in GCE VMs. This can be either HDD or SSD type disks. Standard Hard Disk Drive disks are suitable for handling sequential read/write operations. However, they are not optimized to handle the high rate of IOPS. (Input Output Operations per Second). SSD disks provide a more IOPS rate. The maximum size of a persistent disk is 64TB and a VM can have a maximum of 16 disks in general. More than 16 disks require an SR to GCP.
Characteristics of persistent disks
- Durable network storage devices
- Redundant and optimized performance
- Independent of any compute instances
- Data remains even if instance deleted
- Resizable at any time.
- Does Not span multiple zones/regions
- Auto-Redundancy apply to the same zone/region
Security
All data is encrypted by the GCE before it moves outside of the VM and it is written on the persistent disk. Each persistent disk is encrypted either by system-defined or customer supplied keys.
Once you delete the persistent disk, Google will discard the cipher keys that are matched with the disks and you cannot retrieve the data back at any chance.
Local SSD
Another option that exists in persistent disks is to have the local SSDs, that is physically attached to the server hosted in the VM. Such a device gives more throughput and high performance than standard or SSD disks. However, keep in mind that the local SSDs only stay as long as the instance is up and running. If the instance is stopped or deleted, all data would be lost. At the same time, data would still persist during the instance reboot or live migration.
Each local SSD disk is 375Gig in size and can attach up to 8 local SSD disks.
To add more persistent disks when creating the VM instance, click on the add disks item and select add item,
Mention the disk name and size which is sufficient to add the disk at this stage.
To add a persistent disk to the existing VM instance, follow the next article.