PowerFlex Native Asynchronous Replication RPO with Oracle
Mon, 17 Aug 2020 15:52:45 -0000
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PowerFlex software-defined storage platform provides a reliable, high-performance foundation for mission-critical applications like Oracle databases. In many of these deployments, replication and disaster recovery have become a common practice for protecting critical data and ensuring application uptime. In this blog, I will be discussing strategies for replicating mission-critical Oracle databases using Dell EMC PowerFlex software-defined storage.
The Role of Replication and Disaster Recovery in Enterprise Applications
Customers require Disaster Recovery and Replication capabilities to meet mission-critical business requirements where SLAs require the highest uptime. Customers also want the ability to quickly recover from physical or logical disasters to ensure business continuity in the event of disaster and be able to bring up the applications in minimal time without impact to data. Replication means that the same data is available at multiple locations. For Oracle database environments, it is important to have local and remote replicas of application data which are suitable for testing, development, reporting, and disaster recovery and many other operations. Replication improves the performance and protects the availability of Oracle database application because the data exists in another location. Advantages of having multiple copies of data being present across geographies is that, critical business applications will continue to function if the local Oracle database server experiences a failure.
Replication enables customers in various scenarios such as:
- Disaster Recovery for applications ensuring business continuity
- Distributing with one type of use case such as analytics
- Offloading for mission-critical workloads such as BI, Analytics, Data Warehousing, ERP, MRP, and so on
- Data Migration
- Disaster Recovery testing
PowerFlex Software-Defined Storage – Flexibility Unleashed
PowerFlex is a software-defined storage platform designed to significantly reduce operational and infrastructure complexity, empowering organizations to move faster by delivering flexibility, elasticity, and simplicity with predictable performance and resiliency at scale. The PowerFlex family provides a foundation that combines compute as well as high performance storage resources in a managed unified fabric.
PowerFlex is designed to provide extreme performance and massive scalability up to 1000s of nodes. It can be deployed as a disaggregated storage / compute (two-layer), HCI (single-layer), or a mixed architecture. PowerFlex inclusively supports applications ranging from bare-metal workloads and virtualized machines to cloud-native containerized apps. It is widely used for large-scale mission-critical applications like Oracle database. For information about best practices for deploying Oracle RAC on PowerFlex, see Oracle RAC on PowerFlex rack.
PowerFlex also offers several enterprise-class native capabilities to protect critical data at various levels:
- Storage Disk layer: PowerFlex storage distributed data layout scheme is designed to maximize protection and optimize performance. A single volume is divided into chunks. These chunks will be striped on physical disks throughout the cluster, in a balanced and random manner. Each chunk has a total of two copies for redundancy.
- Fault Sets: By implementing Fault sets, we can ensure the persistent data availability at all time. PowerFlex (previously VxFlex OS) will mirror data for a Fault Set on SDSs that are outside the Fault Set. Thus, availability is assured even if all the servers within one Fault Set fail simultaneously. Fault Sets are subgroup of SDSs installed on host servers within a Protection Domain.
PowerFlex replication overview
PowerFlex software consists of a few important components - Meta Data Manager (MDM), Storage Data Server (SDS), Storage Data Client (SDC) and Storage Data Replicator (SDR). MDM manages the PowerFlex system as a whole, which includes metadata, devices mapping, volumes, snapshots, system capacity, errors and failures, system rebuild and rebalance tasks. SDS is the software component that enables a node to contribute its local storage to the aggregated PowerFlex pool. SDC is a lightweight device driver that exposes PowerFlex volumes as block devices to the applications and hosts. SDR handles the replication activities. PowerFlex has a unique feature called Protection Domain. A Protection Domain is a logical entity that contains a group of SDSs. Each SDS belongs to only one Protection Domain.
Figure 1. PowerFlex asynchronous replication between two systems
Replication occurs between two PowerFlex systems designated as peer systems. These peer systems are connected using LAN or WAN and are physically separated for protection purposes. Replication is defined in scope of a protection domain. All objects which participate in replication are contained in the protection domain, including volumes in Replication Consistency Group (RCG). Journal capacity from storage pools in the protection domain is shared among RCGs in the protection domain.
The SDR handles replication activities and manages I/O of replicated logical volumes. The SDR is deployed on the same server as SDS. Only I/Os from replicated volumes flows through SDR.
Replication Data Flow
Figure 2. PowerFlex replication I/O flow between two systems
- At the source, application I/O are passed from SDS to SDR.
- Application I/O are stored in the source journal space before it is sent to target. SDR packages I/O in bundles and sends them to the target journal space.
- Once the I/O are sent to target journal and get placed in target journal space, they are cleared from source.
- Once I/O are applied to target volumes, they are cleared from destination journal.
- For replicated volumes, SDS communicates to other SDS via SDR. For non-replicated volumes, SDS communicates directly with other SDS.
For detailed information about Architecture Overview, see Dell EMC PowerFlex: Introduction to Replication White Paper.
It is important to note that this approach to replication allows PowerFlex to support replication at extreme scales. As the number of nodes contributing storage are scaled, so are the SDR instances. As a result, this replication mechanism can scale effortlessly from 4 to 1000s of nodes while delivering RPOs as low as 30 seconds and meeting IO and throughput requirements.
Oracle Databases on PowerFlex
The following illustration demonstrates that the volumes participating in replication are grouped to form the Replication Consistency Group (RCG). RCG acts as the logical container for the volumes.
Figure 3. PowerFlex replication with Oracle database
Depending on the scenario, we can create multiple RCGs for each volume pair or combine multiple volume pairs in a single RCG.
In the above Oracle setup, PowerFlex System-1 is the source and PowerFlex System-2 is the destination. For replication to occur between the source and target, the following criteria must be met:
- A volume pair must be created in both source and target.
- Size of volumes in both source and target should be same. However, the volumes can be in different storage pools.
- Volumes are in read-write access mode on the source and read-only access mode in secondary. This is done to maintain data integrity and consistency between two peer systems.
The PowerFlex replication is designed to recover from as low as a 30 seconds RPOs minimizing the data-loss if there is a disaster recovery. During creation of RCG, users can specify RPO starting from 30 seconds to maximum of 60 minutes.
All the operations performed on source will be replicated to destination within the RPO. To ensure RPO compliance, PowerFlex replicates at least twice for every RPO period. For example, setting RPO to 30 seconds means that PowerFlex can immediately return to operation at the target system with only 30 seconds of potential data loss.
The following figures depicts the replication scenario under steady state of workload:
Figure 4. 100% RPO compliance for RPO of 30s for an Oracle database during a steady application workload
Figure 5. Replication dashboard view of PowerFlex
Disaster Recovery
In the case of disaster recovery, the entire application can be up and running by failover to secondary, with less than 30 seconds of data loss.
When we do a planned switchover or failover, the volumes on secondary system are automatically changed to read-write access mode and the volumes on source will be changed to read-only. Consequently, we can bring up Oracle database on secondary by setting up the Oracle environment variables and starting the database.
Once we have RCG in the failover or switchover mode, user can decide how to continue with replication:
- Restore replication: Maintains the replication direction from original source to destination.
- Reverse replication: Changes the direction so that original destination becomes the source and replication will begin from original destination to original source.
PowerFlex also provides various other options:
- Pause and Resume RCG: If there are network issues or user need to perform maintenance of any of the hardware. While paused, any application I/O will be stored at source journal and is replicated to the destination only after the replication is resumed.
- Freeze and Unfreeze RCG: If the user requires consistent snapshot of the source or target volumes. While frozen, replication will still occur between source journal and destination journal, nonetheless the target journal holds on to the data and do not apply them to the target volumes.
PowerFlex native volume replication is a unique solution and provides customers with easy to configure and setup without worrying about disaster.
Irrespective of workload and application, it is designed to support massive scale while providing RPOs as low as 30 seconds.
For more information, please visit: DellTechnologies.com/PowerFlex.
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Important Updates in Dell’s Geographically Dispersed Disaster Restart (GDDR)
Tue, 30 Aug 2022 20:44:56 -0000
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Dell Technologies created Geographically Dispersed Disaster Restart (GDDR) to provide mainframe customers a comprehensive business continuity automation product for their Dell PowerMax Storage and Disk Library for mainframe virtual tape environments. GDDR achieves this by reacting to events within your IT environment.
The three functions of automate, react, and monitor (ARM) combine to enable continuous operations across both planned and unplanned outages. GDDR is designed to perform planned data-center site-switch operations and to restart operations following disasters. These incidents can range from the loss of compute capacity or disk-array access, to the total loss of a single data center, or a regional disaster resulting in the loss of dual data centers. GDDR also provides automation to protect data from cyberattack in a separate physical vault array. For more information about GDDR, see the document GDDR (Geographically Dispersed Disaster Restart) for PowerMax 8000 and VMAX ALL FLASH 950F.
Dell’s GDDR 5.3 enhancements
GDDR introduced an exciting new feature in GDDR 5.3 called Cyber Protection Automation (zCPA) which populates a separate physical cyber vault for your mainframe environment. zCPA automates cyber protection copy creation and preservation by using Dell’s Data Protector for z Systems (zDP). zCPA automates the creation and transmission of PowerMax snapshots to a physically separate cyber vault PowerMax array. This provides a protected copy of data that can be used for testing purposes, recovery from a cyber event, or an analytical process to better understand the extent of damage caused by a cyberattack.
The transmission of data to the cyber vault leverages SRDF/Adaptative Copy. To take advantage of zCPA, customers need GDDR 5.3 with the zCPA PTF, Mainframe Enabler 8.5, and a PowerMax at 5978.711.711 or higher.
Unique benefits of GDDR zCPA types
zCPA supports air gapped and non-air gapped physical cyber vaults. Any site in a GDDR topology can be an attached cyber vault array managed by zCPA. To provide customers choice, there are three types of methods for creating zCPA vault arrays. The three zCPA types are defined by the different configuration and operational attributes that dictate how zCPA will function.
zCPA Type 1
- Type 1 is defined as an environment that has no airgap in connectivity between a data center and the cyber vault. The data copied to the cyber vault is initiated when a newly created zDP Snapset is detected. The cyber vault in Type 1 does not have to be a dedicated physical vault and could be another storage array within the production data center. This type is the default for zCPA.
zCPA Type 2
- Type 2 is an air-gapped environment between two storage environments. The data copied to the cyber vault is triggered by SRDF link online operation. GDDR monitors the SRDF Link Operation process to know when SRDF connectivity to the vault has been established and closed it when it has populated the vault.
zCPA Type 3
- Type 3 is an environment that does not provide an airgap solution. The data copied to the cyber vault is triggered by the SCHEDULE or INTERVAL parameter in GDDR.
The airgap support between the production and vault site is optional.
For more information about GDDR’s zCPA with respect to cyber, see the white paper Dell PowerMax: Cyber Security for Mainframe Storage or contact us at mainframe@dell.com.
Resources
- Mainframe Enablers TimeFinder SnapVX and zDP 8.5 Product Guide
- Data Protector for z Systems (zDP) Essentials White Paper
- Dell PowerMax: Cyber Security for Mainframe Storage
- GDDR (Geographically Dispersed Disaster Restart) for PowerMax 8000 and VMAX ALL FLASH 950F
Author: Justin F. Bastin
New File Services Capabilities of PowerFlex 4.0
Fri, 12 Aug 2022 14:25:22 -0000
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“Just file it,” they say, and your obvious question is “where?” One of the new features introduced in PowerFlex 4.0 is file services. Which means that you can file it in PowerFlex. In this blog we’ll dig into the new file service capabilities offered with 4.0 and how they can benefit your organization.
I know that when I think of file services, I think back to the late 90s and early 2000s when most organizations had a Microsoft Windows NT box or two in the rack that provided a centralized location on the network for file storage. Often it was known as “cheap and deep storage,” because you bought the biggest cheapest drives you could to install in that server with RAID 5 protection. After all, most of the time it was user files that were being worked on and folks already had a copy saved to their desktop. The file share didn’t have to be fast or responsive, and the biggest concern of the day was using up all the space on those massive 146 GB drives!
That was then … today file services do so much more. They need to be responsive, reliable, and agile to handle not only the traditional shared files, but also the other things that are now stored on file shares.
The most common thing people think about is user data from VDI instances. All the files that make up a user’s desktop, from the background image to the documents, to the customization of folders, all these things and more are traditionally stored in a file share when using instant clones.
PowerFlex can also handle powerful, high performance workload scenarios such as image classification and training. This is because of the storage backend. It is possible to rapidly serve files to training nodes and other high performance processing systems. The storage calls can go to the first available storage node, reducing file recall times. This of course extends to other high speed file workloads as well.
Beyond rapid recall times, PowerFlex provides massive performance, with 6-nines of availability1, and native multi-pathing. This is a big deal for modern file workloads. With VDI alone you need all of these things. If your file storage system can’t deliver them, you could be looking at poor user experience or worse: users who can’t work. I know, that’s a scary thought and PowerFlex can help significantly lessen those fears.
In addition to the performance, you can manage the file servers in the same PowerFlex UI as the rest of your PowerFlex environment. This means there is no need to learn a new UI, or bounce all over to set up a CIFS share—it’s all at your fingertips. In the UI it’s as simple as changing the tab to go from block to file on many screens.
The PowerFlex file controllers (physical) host the software for the NAS servers (logical). You start with two file controllers and can grow to 16 file controllers. Having various sizes of file controllers allows you to customize performance to meet your environment’s needs. The NAS Servers are containerized logical segmentations that provide the file services to the clients, and you can have up to 512 in a cluster. They are responsible for namespaces, security policies, and serving file systems to the clients.
Each of the file volumes that are provided by the file services are backed by PowerFlex volumes. This means that you can increase file service performance and capacity by adding PowerFlex nodes to the storage layer just like a traditional block storage instance. This allows you to independently scale performance and capacity, based on your needs.
The following table provides some of the other specs you might be wondering about.
Feature | Max |
FS Capacity | 256 TB |
Max file size | 64 TB |
# of files | 10 billion |
# of ACLs | 4 million |
User File Systems | 4096 |
Snaps per File System | 126 |
CIFS | 160000 |
NFS exports | 80000 |
Beyond the architectural goodness, file storage is something that can be added later to a PowerFlex environment. Thus, you aren’t forced to get something now because you “might” need it later. You can implement it when that project starts or when you’re ready to migrate off that single use file server. You can also grow it as you need, by starting small and growing to a large deployment with hundreds of namespaces and thousands of file systems.
With PowerFlex when someone says “file it,” you’ll know you have the capacity to support that file and many more. PowerFlex file services provide the capability to deliver the power needed for even the most demanding file-based workloads like VDI and AI/ML data classification systems. It’s as easy managing the environment as it is integrated into the UI.
If you are interested in finding out more about PowerFlex file services, contact your Dell representative.
Author: Tony Foster
Twitter: @wonder_nerd
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1 Workload performance claims based on internal Dell testing. (Source: IDC Business Value Snapshot for PowerFlex – 2020.)