Overview
DBox Migration provides the ability to migrate data from older DBoxes to new units, and then remove the older units from the Cluster. This allows newer hardware to be added to the cluster, and remove older hardware.
Once set up, the migration process is managed by VMS as a background process while at the same time the data in the cluster is fully accessible (including that in the DBoxes that are marked for migration and removal). If several DBoxes are marked for migration, data is moved from each in turn, and then the unit is removed from the cluster and powered off. The process can take several days, depending on the number and size of the units to be migrated, and the loading on the cluster.
The migration process is different from the Replace DBox procedure. The Replace DBox procedure replaces faulty DBox units but retains the SSDs and SCM from them (they are physically moved from the older DBox to the new units).
Prerequisites
These prerequisites must be met in order to migrate DBoxes:
Replacement storage must be equivalent or exceed the storage of the DBoxes that are being migrated and removed (SSD, SCM, memory). It can be different in units, sizes etc, but the total new storage must match or exceed the amount being removed.
For example: you can replace single DBox with 10TB with two new DBoxes with 5TB each, or 2 DBoxes with 5TB can be replaced by single new one with 10TB.
Note
VMS requires a minimum number of DBoxes (for HA). A DBox migration will not take place if the proposed migration would reduce the number of DBoxes below this minimum (for example, if several existing DBoxes are replaced with fewer new DBoxes).
New DBoxes must be added to the cluster following DBox HW installation steps (without activating them).
The cluster must have sufficient spare capacity (default is 7%) at the start of the migration (not including the storage capacity of the new DBoxes) in order to start the migration. During the course of the migration, spare storage capacity cannot fall below another level (default 5%). These settings can be adjusted by users.
Note
This is a requirement for the migration process, even though the replacement DBoxes add storage capacity.
The cluster is not in the process of one of the following: software upgrade, DBox replacement, system expansion, rewriter operations.
During the Migration
The migration process can take up to 36 hours for each DBox (depending on cluster IO loading during the migration, and the amount of data to be transferred from the retired DBox).
VMS limits the transfer speed from the retired DBox storage, to permit normal cluster IO activity without significant performance degradation.
Status of the Cluster During Migration
Cluster storage (including the migrated DBoxes) is fully available for normal R/W activity during the migration.
VMS regulates the migration process to ensure sufficient performance in the cluster for normal IO activity.
Termination of Migration
You cannot manually terminate the migration process once it has started.
VMS halts the migration process if a condition occurs during the migration that prevents it continuing - e.g insufficient spare capacity, or a fault with the DBox etc. If this occurs this is the status of the DBoxes:
DBoxes that have been migrated and phased-out (and powered off) remain phased out.
DBoxes for which the migration has not yet started remain active in the Cluster.
The DBox that is in progress of migration at the time of termination remains Read-Only. The migration can be resumed on it.
Migrating DBoxes using the VAST Web UI
Unpack and rack mount each new DBox in one of the cluster's current racks or an adjacent rack. For help with these tasks, see the Hardware Install Guide. For specific guidance regarding rack mount positions, consult your Sales Engineer.
Consult your Sales Engineer on the correct cabling scheme and connect the new CNodes and DNodes to correctly configured designated switch ports, using appropriate NIC ports and cables.
On the VAST Web UI navigate to Infrastructure, and then select the DBoxes tab.
Select Manage Infrastructure, and then select Migrate DBoxes. This opens the Migrate DBox dialog.
Select the DBoxes to be replaced. At the top of the list the number of selected DBoxes and the cumulative amount of storage capacity they represent is adjusted,
When done, click Start Discovery To Find New Hardware To Add, at the bottom. VMS scans for new DBox hardware.
Select the new DBoxes to be added to the cluster as replacements, from the list of DBoxes. At the top of the list, the number of selected DBoxes and the cumulative amount of storage capacity they represent is adjusted.
Click Start Migration Process Now.
Alternatively, click Save For Later to pause the configuration of the migration and save details. You can resume the process at a later time, using the saved details.
Click Confirm to start the migration process. The migration proceeds in the background. The indication MIgration in Process appears in the upper right of the DBoxes screen.
While the migration is in progress you can perform other actions on the cluster, and use the cluster storage normally. The DBoxes marked to be replaced are set as Read-Only (writes to them will cause the blocks to be copied to another location in storage).
As each DBox is migrated, it is removed from the cluster and powered off (this appears in the status of the DBox).