GCP Persistent Disk Storage

            
 

            

        

          

     
          

         

                 
          
 





  
  

      
Persistent Disk is Google Cloud's durable, high-performance block storage service. It serves as the virtual hard drive for your Virtual Machine (VM) instances. Unlike ephemeral storage, Persistent Disks exist independently of the VM; data persists even if the instance is terminated.


    
1. Key Characteristics

    
    
        
  • Network-Attached: Connected via Google’s high-speed network, allowing disks to be easily detached and moved between VMs in the same zone.
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  • High Availability: Data is automatically replicated multiple times within a zone to protect against hardware failure.
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  • Incremental Snapshots: Create point-in-time backups that only store data changed since the last snapshot, saving time and costs.
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  • Hot Resizing: Increase disk capacity on-the-fly without rebooting or detaching the disk.
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2. Comparison of Disk Types

    

        
            

                Disk Type
                Performance
                Ideal Use Case
            

        
        
            

                Standard (pd-standard)
                HHDD-backed
                Large data processing, cold storage, backups.
            

            

                Balanced (pd-balanced)
                Solid
                General-purpose workloads, boot disks, web servers.
            

            

                SSD (pd-ssd)
                High
                Relational databases (SQL), enterprise applications.
            

            

                Extreme (pd-extreme)
                Ultra
                SAP HANA, Oracle, massive I/O workloads.
            

        
    



    
3. Practical Example: Database Scaling

    
Imagine your database is outgrowing its server capacity. Because you used a Persistent Disk:

    
    
        
  • You can take a Snapshot of the disk for safety.
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  • You can shut down the current VM, detach the disk, and attach it to a much larger N2 High-Mem machine.
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  • Your data is exactly where you left it, with zero data migration or manual file transfers required.
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4. Steps for Using Persistent Disk in GCP

    
    

        Phase 1: Create and Attach (Console)
        
    
            
  1. Go to Compute Engine > Storage > Disks and click Create Disk.
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  2. Select the same Zone as your VM and define the size.
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  3. Go to VM instances, edit your instance, and under Additional disks, click Attach existing disk.
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        Phase 2: Configuration (OS Level via SSH)
        
After attaching, you must prepare the disk for use with these commands:

        

            # 1. Format the disk (Warning: deletes existing data)

            sudo mkfs.ext4 -m 0 -E lazy_itable_init=0,discard /dev/sdb


            # 2. Create a mount point directory

            sudo mkdir -p /mnt/disks/data-storage


            # 3. Mount the disk

            sudo mount -o discard,defaults /dev/sdb /mnt/disks/data-storage