The document discusses the importance of persistent storage for containerized applications, detailing types of persistent volumes and their access modes. It highlights the need for persistent storage due to containers being stateless and the necessity to retain data across runs. Various storage options, including NFS, iSCSI, and GlusterFS, are presented, along with their respective performance characteristics and use cases.

1. Selecting the Right Persistent Storage Options for Apps in
Containers
Bipin Kunal & Niels de Vos, Red Hat

2. Who are Bipin and Niels?
Bipin:
Product lead for Gluster Support and Maintenance
Engineer.
Niels:
Developer and Maintainer at the Gluster community
and involved in related projects.

3. Agenda
• What is persistent storage
• Why do we need persistent storage
• Type of persistent volumes
• Access modes for your PVs
• Performance details between different Access Modes

4. What is Persistent Storage?
● Persistent storage is any data storage device
that retains data after power to that device is
shut off.

5. Why do we need persistent storage?
• Containers are mostly stateless, but produce or
gather data for later consumption.
• Containers may not always be running or
available, the data should be kept so that a next
run can continue where it left off.

6. POD
RHGS
POD
RHGS
POD
RHGS
POD
RHGS
POD
INFRA
POD
INFRA
PERSISTENT
VOLUME CLAIM
OpenShift: Container-Native Storage

7. NFS
iSCSI
Azure Disk
GCE Disk
Ceph RBD
GlusterFS
AUTOMATED CONFIGURATION
SINGLE CONTROL PANEL
CHOICE OF PERSISTENT STORAGE
Amazon EBS
Storage Options for OpenShift

8. NFS WELL UNDERSTOOD, EASY TO DEMO
PROVIDES RWX STORAGE
NO HA, NOT AVAILABLE IN THE CLOUD
REQUIRES PRE-PROVISIONING
Storage Options for OpenShift: NFS

9. WELL UNDERSTOOD IN THE DC
BLOCK STORAGE, NO RWX SUPPORT
NOT AVAILABLE IN THE CLOUD
REQUIRES PRE-PROVISIONING
iSCSI
NFS
Storage Options for OpenShift: iSCSI

10. AVAILABLE IN THE CLOUD ;)
NOT AVAILABLE ACROSS AZs
PERFORMANCE DEPENDS ON SIZE
BLOCK STORAGE, NO RWX SUPPORT
Amazon EBS
Azure Disk
GCE Disk
iSCSI
NFS
Storage Options for OpenShift: Cloud Provider Storage

11. BLOCK STORAGE, NO RWX SUPPORT
SCALABLE, HA
CINDER PREFERRED FOR OCP on OSP
Ceph RBD
Amazon EBS
Azure Disk
GCE Disk
iSCSI
NFS
Storage Options for OpenShift: Ceph

12. GlusterFS
RUNS ON TOP OF OPENSHIFT
AVAILABLE OUT OF THE BOX
SCALABLE FILE STORAGE, RWX SUPPORT
AVAILABLE EVERYWHERE
GEO-REPLICATION, SNAPSHOTS
Ceph RBD
Amazon EBS
Azure Disk
GCE Disk
iSCSI
NFS
Storage Options for OpenShift: Gluster

13. Access modes for your PV’s
• ReadWriteOnce (RWO)
– Single node is allowed to read/write
• ReadOnlyMany (ROX)
– Multiple nodes can read at the same time
• ReadWriteMany (RWX)
– Multiple nodes can read and write at the same time

14. ReadWriteOnce (RWO)
• Applications that do not need to share a
filesystem among instances
• Optimizations possible, block-storage mounted
in the container
• Fewer filesystem operations, only read/write
data

15. ReadOnlyMany (ROX)
• Static content that was generated
• Snapshot of RWO/X promoted to ROX
• Read-only mounted NFS-export

16. ReadWriteMany (RWX)
• Dropbox like applications, Wordpress with
uploading images, Jenkins Artifacts
• Performs best with limited create/write, many
read
• Mounted NFS-export

17. Example: ReadWriteMany (RWX)
• Mounted NFS-export
• 'git clone /srv/glusterfs.git' into the mountpoint
• Repository after clone ~80 MB
50 seconds, 17133 NFSv4 operations

18. Example: ReadWriteOnce (RWO)
• Disk-image stored on NFS-export
• Mounted NFS-export on the host
• Mounted (loopback) disk-image on the host
< 1 second, ~1 NFSv4 operation
8 seconds, 195 NFSv4 operations (+ sync)

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