Lets learn what advance configuration we can do in Zerto. Advance setting dialog box help us to configure all setting we couldn’t do during express installation.
Where are advance settings?
Advance setting screen as shown above can been seen on first page top right hand corner (gear icon.)
What all you can configure in advance settings?
You can configure
- vCloud Director connection
- Provide vDC connection
- Bandwidth throttling (discussed in detailed below)
- Enable replication to same site when single vCenter is managing both the sites
- Replication pause time (discussed in detailed below)
- and many other settings e.g. email notification
You can also get to see the compatibility matrix of the product with ESXi
This is bit important settings to discuss. Suppose you have 100 Mbps of bandwidth between the sites. Network team is allowing only 50 Mbps of dedicated bandwidth. In such scenario this feature is highly useful. You can move slider to throttle bandwidth up to 50 Mb/sec or 50/8=6.25 MB/sec
50 Mbps usage can be further prioritize using VPG priority (QoS) group.
let discuss it via simple example
VM1 is in High Priority group
VM2 is in Medium Priority group
VM3 is in low priority group
VM1 (Belongs to high priority VPG) has changed significantly and it is consuming 70% of bandwidth. VM2 (Belongs to medium priority VPG) will use entire 30% bandwidth if it needs and whatever is remaining is left for low priority VPG i.e. VM3. In case nothing is left, Low VPG has to wait till it gets bandwidth to replicate.
Unfortunately no ratio is defined between High:Medium:Low priority VPG. Therefore it is more of High always gets priority over Medium and Medium always gets priority over Low.
Minimum bandwidth supported is 5 Mb/sec
Time-based Bandwidth Throttling
You also have more granular option where you can choose when bandwidth throttling is needed. In below figure we can throttle between 0100 till 0600 hrs
Defining Replication Pause Time
In order to understand this you will need to understand what is Journaling and how does it maintains Journal history. Let me help you with the simple figure below
In above figure VM replicates all latest changed to the Journal. By default history of 4 hours is kept in Journal volumes. These are basically check points which gives you freedom to restore to any point in that four hours. After 4 hours, all check point which are older than four hours gets merged with VMDK of replicated VM i.e. effectively deleted
Lets discuss this with an example
|1 GB File Copied||1st Hour|
|1 GB File Deleted||2nd Hour|
|Copied office 2013||3rd Hour|
|Copied Sharepoint 2013||4th Hour|
If replication has succeeded all four check points will be available in the journal.
But in case if 1 GB file copied in 1st hour takes 4 hour to replicate, 1 GB file’s checkpoint is deleted and over written by 2nd hour operation. This is occurs as 4 hour journal history period has elapsed. No checkpoints are available, therefore no point in time recovery would be possible.
So by pausing replication setting will assist you to eliminate this problem. If you provide a pause time of 30 min, chances of losing check points are reduced by 30 mins. One scenario I could imagine this would occur is when journal datastore becomes full
In Next post lets discuss how to monitoring VPG
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