Docker 101 - Part3 - Persisting data using volumes

In this article, I will explain how to use Docker volumes for persisting data generated by and used by containers with --mount flag. Volumes use the Docker area and it can be found under /var/lib/docker/volumes/ directory of the Docker host.

Example:

docker run -dit --name centos_volume_test --mount source=data_volume01,target=/datavol01 centos sleep 1800

The above command will run a CentOS container and mounts a volume at /datavol01 inside the container. It uses source /var/lib/docker/volumes/data_volume01. The below screenshot shows the necessary steps to verify it.

Hope it was useful. Cheers!

Related posts

Docker 101 - Part2 - Basic operations

Docker 101 - Part1 - Installation

References

https://docs.docker.com/storage/volumes/

https://docs.docker.com/storage/bind-mounts/

Storage Spaces Direct - Volumes and Resiliency

Storage Spaces Direct (S2D) is the Microsoft implementation of software defined storage (SDS). This article briefly explains about the different types of volumes that can be created on a S2D cluster. Once you enable S2D using Enable-ClusterS2D cmdlet, it will automatically claim all physical disks in the cluster and forms a storage pool. On top of this pool you can create multiple volumes which is explained below.

Mirror

• Recommended for workloads that have strict latency requirements or that need lots of mixed random IOPS
• Eg: SQL Server databases or performance-sensitive Hyper-V VMs
• If you have a 2 node cluster: Storage Spaces Direct will automatically use two-way mirroring for resiliency
• If your cluster has 3 nodes: it will automatically use three-way mirroring
• Three-way mirror can sustain two fault domain failures at same time

new-volume -friendlyname "Volume A" -filesystem CSVFS_ReFS -storagepoolfriendlyname S* -size 1TB

• You can create two-way mirror by mentioning "PhysicalDiskRedundancy 1"

new-volume -friendlyname "Volume A" -filesystem CSVFS_ReFS -storagepoolfriendlyname S* -size 1TB -PhysicalDiskRedundancy 1

Parity

• Recommended for workloads that write less frequently, such as data warehouses or "cold" storage, traditional file servers, VDI etc.
• For creating dual parity volumes min 4 nodes are required and can sustain two fault domain failures at same time

new-volume -friendlyname "Volume B" -filesystem CSVFS_ReFS -storagepoolfriendlyname S* -size 1TB -resiliencysettingname Parity

• You can create single parity volumes using the below

new-volume -friendlyname "Volume B" -filesystem CSVFS_ReFS -storagepoolfriendlyname S* -size 1TB -resiliencysettingname Parity -PhysicalDiskRedundancy 1

Mixed/ Tiered / Multi-Resilient (MRV)

• In Windows Server 2012 R2 Storage Spaces, when you create storage tiers you dedicated physical media devices. That means SSD for performance tier and HDD for capacity tier
• But in Windows Server 2016, tiers are differentiated not only by media types; it can include resiliency types too
• MRV = Three-way mirror + dual-parity
• In a MRV, three-way mirror portion is considered as performance tier and dual parity portion as capacity tier
• Recommended for workloads that write in large, sequential, such as archival or backup targets
• Writes land to mirror section of the volume and then it is gradually moved/ rotated in to parity portion later
• Each MRV by default will have 32 MB Write-back cache 
• ReFS starts rotating data into the parity portion at 60% utilization of the mirror portion and gradually as utilization increases the speed of data movement to parity portion also increases
• You should have min 4 nodes to create a MRV

new-volume -friendlyname "Volume C" -filesystem CSVFS_ReFS -storagepoolfriendlyname S* -storagetierfriendlynames Performance, Capacity -storagetiersizes 1TB, 9TB

References:

Microsoft

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