Announced at Google I/O in June 2014, Local SSD moved from beta into general availability mode. These persistent disks deliver high number of IOPS when compared to other block storage choices available in Google Compute Engine.
Customers can attach up to 4 SSD partitions to a VM with maximum supported disk size of 375GB. Only full core VMs support Local SSD disks. Shared-core machine types such as f1-micro and g1-small cannot be used with these disks. Local SSD performance delivers up to 680,000 read IOPS and 360,000 write IOPS with a latency that is below 1 millisecond. Local SSD disks are always encrypted to ensure data protection. Given the high throughput, these disks are ideal for database workloads that replicate data between multiple local SSD instances. Hadoop deployments that demand higher IOPS can also take advantage of these disks. Other use cases include temporary storage and cache servers. The NoSQL database company, Aerospike claims to achieve enhanced performance with Local SSD. Aerospike Certification Test (ACT) for SSDs on Google Compute Engine demonstrated 15x storage cost advantage and RAM-like performance with Local SSDs.
Google Compute Engine has 3 types of block storage - standard persistent disk, SSD persistent disk and Local SSD disks. Unlike the first two, Local SSD doesn’t have redundancy. The other key difference is that the Local SSD allows users to create instances with block storage that is physically attached to the virtual machine host server. This ensures higher IOPS than other disk types.
CloudHarmony, an independent performance benchmarking company has published a report that shows Google Compute Engine VMs with Local SSD delivering the highest number of 4K random IOPS across all of the available VM-storage combinations on the public cloud.
Local SSD disks come with a few restrictions. They can only be created during instance creation, and they are deleted when an instance is terminated. It is not possible to attach or detach a local SSD or to keep a local SSD longer than the lifetime of the instance. A local SSD cannot be used as a boot disk and a virtual machine using local SSD must have a separate (persistent) root disk.
Local SSDs are available in all zones except us-central1-b and europe-west1-a. Pricing information can be found here.