Emc bcsd tool

The key to this is to make the host cluster believe there is no distance between the nodes so they behave identically as they would in a single data center. Going forward throughout this document it is assumed that there is a stretched layer 2 network between datacenters where a VPLEX Metro resides.

This therefore means that all the rules associated with a single disk are fully applicable to a VPLEX Metro distributed volume. For instance, the following figure shows a single host accessing a single JBOD type volume: Datacenter Figure 3 Single host access to a single disk Clearly the host in the diagram is the only host initiator accessing the single volume.

The next figure shows a local two node cluster. Cluster of hosts coordinate for access Datacenter Figure 4 Multiple host access to a single disk As shown in the diagram there are now two hosts contending for the single volume. This means that the hosts are still required to coordinate locking to ensure the volume remains consistent.

When using FC connectivity this can be configured with either a dedicated channel i. It is assumed that any WAN link will have a second physically redundant circuit. Please engage your EMC account team to perform a sizing exercise.

There are three main items that are required to deliver true "Federated Availability". Synchronous mirroring to ensure both locations are in lock step with each other from a data perspective. External arbitration to ensure that under all failure conditions automatic recovery is possible. In the previous sections we have discussed 1 and 2, but now we will look at external arbitration which is enabled by VPLEX Witness.

It is the preference rule that determines the outcome after failure conditions such as site failure or link partition. The preference rule can either be set to cluster A preferred, cluster B preferred or no automatic winner. Note: Fault domain is decided by the customer and can range from different racks in the same datacenter all the way up to VPLEX clusters 5ms of distance away from each other 5ms measured round trip time latency or typical synchronous distance.

The current supported maximum round trip latency for this is 1 second. For instance if the VPLEX Metro clusters are to be deployed into the same physical building but perhaps different areas of the datacenter, then the failure domain here would be deemed the VPLEX rack itself. It does however become a crucial component to ensure availability in the event of site loss at either of the locations where the VPLEX clusters reside.

To minimize this risk, it is considered best practice to disable the VPLEX Witness function if it has been lost and will remain offline for a long time. The storage that the VPLEX Witness uses should be physically contained within the boundaries of the third failure domain on local i.

Additionally it should be noted that currently HA alone is not supported, only FT or unprotected. This is mandatory to ensure fully automatic i. This ensures that fabrics do not merge and span failure domains. Another important note to remember for cross-connect is that it is only supported for campus environments up to 1ms round trip time.

It is best practice to ensure that the pathing policy is set to fixed and mark the remote paths across to the other cluster as passive. This ensures that the workload remains balanced and only committing to a single cluster at any one time. Since VPLEX is architecturally unique from other virtual storage products, two simple categories are used to easily distinguish between the architectures.

The terms are defined as follows: 1. To understand this in greater detail and to quantify the benefits of non-uniform access we must first understand uniform access. The first thing to note here is that we now only have a single controller at either location so we have already compromised the local HA ability of the solution since each location now has a single point of failure.

The next challenge here is to maintain host access to both controllers from either location. If the only active storage controller resides at A, then we need to ensure that hosts in both site A and site B have access to the storage controller in site A uniform access. This is important since if we want to run a host workload at site B we will need an active path to connect it back to the active director in site A since the controller at site B is passive.

Additionally we will also require a physical path from the ESXi hosts in site A to the passive controller at site B. The diagram in Figure 10 below shows a typical example of a uniform architecture. The steps below correspond to the numbers in the diagram. The acknowledgment from back end disk returns to the owning storage controller.

The concern here is that each write at the passive site B will have to traverse the link and be acknowledged back to site A. This ultimately increases the response time i. Both write acknowledgments are sent back to the active controller back across the ISL 6. VPLEX was built from the ground up for extremely efficient non-uniform access.

This means it has a different hardware and cache architecture relative to uniform access solutions and, contrary to what you might have already read about non-uniform access clusters, provides significant advantages over uniform access for several reasons: 1.

This ensures minimal up to 3x better compared to uniform access response time and bandwidth regardless of where the workload is running. A cross-connection where hosts at site A connect to the storage controllers at site B is not a mandatory requirement unless using VMware FT. This is another key difference when compared to uniform access since if the primary active node is lost a failover to the passive node is required.

Some other key differences to observe from the diagram are: 1. VPLEX has multiple active controllers in each location ensuring there are no local single points of failure. VPLEX uses and maintains single disk semantics across clusters at two different locations. Note: Under some conditions depending on the access pattern, VPLEX may encounter what is known as a local write miss condition. This does not necessarily cause another step as the remote cache page owner is invalidated as part of the write through caching activity.

In effect, VPLEX is able to accomplish several distinct tasks through a single cache update messaging step. Your mileage will vary. And so we have to use it as a learning tool to prevent them from re-offending or doing things again. The superintendent and the board are going to proactively support students going through disciplinary action, Bayer said.

When discipline is so punishing, and kids don't see any hope they never come back, the superintendent said they could continue to go down the wrong path. We want it to be there to support kids, if they are dealing with an issue. It just needs to be communicated better, and how they connect, and where you find them all need to be in one location instead of all the policy. Bayer said the district just started the process to update the document, which is expected to take three months.

Each series has to go through three readings, which takes three months, Bayer said. BCSD has organized policies by topic and places them in series, by numbers. The series go from series to , which can include anything from one to 1, different policies. It will be another year before all policies are rewritten. At the Jan. The second half of the series will be brought for its first reading at the February meeting.

The example here is to give you an idea of the planning behind the capacity requirements. While the above calculation is used for sizing capacity of the Journal my next blog will detail the performance characteristics required by both the Journal and Replica volumes. Reblogged this on PhenoRhapsody.

What kind of rollback time is it hoping to provide? What makes it a good rule of thumb? It seems this would be highly variable. You are commenting using your WordPress. You are commenting using your Google account.

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