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Filesystem checkpoints provide a point in time image of a given file system. This allows system administrators and eNAS users to return a file system to a given point in time, in order to recover lost or corrupt data, and to perform a variety of tasks on the data from this point in time. If checkpoints are required for eNAS, use SnapSure.
SnapSure enables you to create point-in-time logical images of a production file system. SnapSure uses a "copy on first modify" principle. A production file system consists of blocks. When a block within the production file system is modified, a copy containing the block’s original contents is saved to a separate volume called the SavVol. Subsequent changes made to the same block in the production file system are not copied to the SavVol. The original blocks from the production file system in the SavVol and the unchanged production file system blocks remaining in the production file system are read by SnapSure according to a bitmap and blockmap data-tracking structure. These blocks combine to provide a complete point-in-time image called a checkpoint.
Checkpoints can be read-only or read/write. With SnapSure, you can restore a production file system to a point in time either type of checkpoint. Create checkpoints using the data protection tab in Unisphere for VNX. In Unisphere, you select the file system, the checkpoint name, and the pool to use for storing the checkpoints. Use Unisphere for VNX to schedule automated snapshots, allowing at least 15 minutes between snapshots.
If using NDMP backups, configure these two schedules so that they do not overlap.
Every checkpoint you create, is another file system, so it is important to take into account the number of file systems you are going to create when creating or scheduling checkpoints.
eNAS supports Virtual Data Movers (VDMs). VDMs are used for isolating Data Mover instances within a secure logical partition. They are file system containers that isolate a Virtual Data Mover from other VDMs in the same Data Mover container. VDM is a security mechanism as well as an enabling technology that simplifies the disaster recovery failover process. It maintains file system context information (metadata) to avoid rebuilding these structures on failover. File systems can be mounted beneath VDMs that are logically isolated from each other. VDMs can be used to support multiple LDAP domains within a customer environment. They can also be used to rebalance file loads across physical Data Movers by moving VDMs and their underlying file systems between Data Movers. VDMs are important when deploying replication solutions.
Introduced in the HYPERMAX OS 5977.691.684, File Auto Recovery (FAR) allows you to manually failover or move a Virtual Data Mover (VDM) from a source eNAS system to a destination eNAS system. The failover or move leverages block-level Symmetrix Remote Data Facility (SRDF) synchronous replication, thus there is zero data loss in the event of an unplanned operation. This feature consolidates VDMs, file systems, file system checkpoint schedules, CIFS servers, networking, and VDM configurations into their own nas_pools. This feature works for a recovery where the source is unavailable. For recovery support in the event of an unplanned failover, there is an option to recover and clean up the source system and make it ready as a future destination.
VDM failover can be run as a planned activity, or as a disaster recovery exercise. There are two different commands that can be run, depending on which scenario the administrator may be in:
The manually initiated failover and reverse options can also be performed using the Dell EMC File Auto Recovery Manager (FARM) product. This product allows the ability to automatically failover Syncreplicable VDMs from a source to a target destination. FARM can be configured to monitor sync-replicated VDMs and trigger automated failover in the event of Data Mover, File System, Control Station or IP network unavailability, that would cause data unavailability to the eNAS client.
If users are configuring your CIFS shares with Continuous Access (CA) you need to create an additional interface with connectivity to your domain controller (DC) to ensure that you do not lose access to your CIFS share when performing the first failover.
The Data Mover must always have access and be able to communicate with the DC to allow seamless failover of CA enabled CIFS shares. This can be achieved by configuring an additional interface on the DM of the remote site, prior to performing the first failover.
For all additional failovers, you need to ensure that the remote site, has an interface configured and active on it, prior to performing the failover.
FAR can be used for disaster recovery, maintenance and load-balancing operations. FAR has the following requirements:
See the support documentation for FAR: https://www.dellemc.com/en-us/collaterals/unauth/technical-guides-support-information/products/storage/docu88921.pdf
eNAS supports traditional NAS backup applications, for example Dell EMC Networker or Dell EMC Avamar, which can both be found in the Dell EMC Data Protection Suite.
Further information about these solutions can be found at:
Note: A dedicated 8 Gb I/O module is required for NDMP backups.
eNAS upgrades are performed during overall PowerMaxOS upgrades. During eNAS upgrades, the new code is deployed to the DMs, and a reboot of them is required to install the new code versions. The user has two options here:
There are many factors to consider here, including:
Testing has shown that some I/O generators will not experience interruptions during these reboots. However, it is up to you to determine the type of workload that is running, and to determine if it can withstand the duration of outage that may be caused by the number of file systems to be failed over.