Free D-MSS-DS-23 Practice Test Questions and Answers (2026) Practice Questions

The Dell PowerStore Sizer tool requires key performance indicators to characterize a workload for accurate system sizing. Throughput (MB/s) is a primary input that defines the required data transfer rate, essential for bandwidth-intensive operations like backups or analytics. Response Time (ms) is another critical input, specifying the latency tolerance for I/O requests, which is vital for transactional applications like databases. Sizer uses these user-defined values, along with IOPS and I/O profile, to model the workload's demands and ensure the proposed configuration can meet the required performance service levels.

B. Frontend Performance Saturation: This is a calculated output metric in Sizer that indicates the projected load on the system's front-end components, not a workload input parameter.

D. Storage Performance Saturation: This is an output metric from the Sizer tool that shows the projected utilization of backend storage resources, not an input to define workload performance.

1. Dell PowerStore: Sizing Guide (Internal Dell Technologies & Partner Document). The "Workload Entry" section for creating custom workloads explicitly lists "Throughput (MB/s)" and "Response Time (ms)" as fundamental input parameters required to define the performance characteristics of the application being sized.

2. Dell PowerStore: Best Practices Guide, Page 8, Section "Performance". This document emphasizes understanding application workload characteristics, stating, "Key metrics to understand for each application workload include IOPS, throughput, and latency (response time) requirements." This confirms that Throughput and Response Time are primary metrics used to define and size for a workload. The Sizer tool is built upon these fundamental principles.

Dell Unity XT dynamic pools are designed with flexibility for expansion. When adding new drives to an existing dynamic pool, the system supports mixing drives of different sizes, provided they are of the same type (e.g., all SSDs). The underlying architecture of dynamic pools divides all physical drive space into small, manageable extents. This allows the system to aggregate the total capacity from all drives, meaning the full capacity of the new, larger 3.84 TB drives will be added to the pool's usable capacity without being truncated to match the size of the original drives.

B. Only half of the capacity of the new drives will be available.

This is incorrect. This behavior (truncating capacity to the smallest drive size) is characteristic of traditional RAID groups, not the more advanced Dell Unity dynamic pools.

C. Three of the drives will be added with a fourth reserved as spare.

This is incorrect. Dynamic pools utilize a distributed sparing model where spare capacity is reserved across all drives in the pool, rather than dedicating an entire drive as a hot spare.

D. The mixing of drive types is not supported, and the operation will fail.

This is incorrect. Mixing drive sizes within the same technology type (e.g., SAS SSD) is a supported and documented feature for expanding dynamic pools on Dell Unity XT systems.

1. Dell Unity: Dynamic Pools White Paper (H15093.7)

Page 13, Section: Pool Expansion: "Drives of different sizes can be added to the pool, and the full capacity of the new drives is available for use. This is because the entire pool is virtualized, and all drive space is broken down into small extents. This allows the system to use all the space on all the drives, regardless of their size." This directly supports answer A and refutes B and D.

Page 10, Section: Sparing: "Dynamic pools utilize a distributed sparing technology... Instead of dedicating entire drives to be on standby in case of a failure, spare space is distributed across all the drives in the dynamic pool." This refutes answer C.

2. Dell Unity Family Unisphere Online Help (Version 5.3)

Section: Add storage to a pool: The documentation outlines the process for expanding a pool and lists the compatibility rules. It states, "For dynamic pools, you can add drives of a different size than the drives that are already in the pool, as long as the new drives are of the same drive technology." This confirms that the operation is supported, refuting option D.

Jumbo frames increase the Ethernet frame Maximum Transmission Unit (MTU) from the standard 1500 bytes to a larger size, typically 9000 bytes. For block storage protocols like iSCSI, this allows more payload data to be sent in a single frame. This reduces the number of frames and protocol headers that need to be processed by the host, network switches, and the Unity XT array. The result is lower CPU overhead on all components and increased network throughput, providing the best performance for iSCSI traffic. For this benefit to be realized, jumbo frames must be configured end-to-end.

A. iSCSI offload is a host-side hardware feature (iSCSI HBA or TOE) that reduces host CPU utilization; it is not a network configuration option in the same context as MTU.

B. A single VLAN for all traffic types is against best practices. It creates network congestion and security risks by mixing storage, management, and other traffic, which degrades performance.

C. Disabling flow control is detrimental. Flow control prevents packet loss during periods of congestion; disabling it can cause TCP retransmissions, which severely degrade iSCSI performance.

1. Dell Technologies. (2022). Dell Unity: Best Practices Guide. (Technical White Paper H15163.7). Page 21, Section "iSCSI Considerations", Subsection "Jumbo Frames". The document states, "Jumbo Frames allow Ethernet frames to carry a larger payload, increasing the efficiency of the protocol... For the best performance, it is recommended to enable Jumbo Frames on the host, network, and storage system."

2. Dell Technologies. (2022). Dell Unity: Best Practices Guide. (Technical White Paper H15163.7). Page 21, Section "iSCSI Considerations", Subsection "Flow Control". The guide recommends, "It is recommended to enable Flow Control on the network switches to prevent packet drops." This refutes option C.

3. Dell Technologies. (2019). Dell EMC Unity Family: Configuring iSCSI. (Docu92193). Page 10, Section "Jumbo frames". This guide states, "For optimal performance, Dell Technologies recommends enabling jumbo frames on the iSCSI ports on the storage system, on the network switches, and on the hosts."

4. Dell Technologies. (2022). Dell Unity: Best Practices Guide. (Technical White Paper H15163.7). Page 20, Section "Network Considerations", Subsection "VLANs". The guide advises, "It is recommended to use VLANs to segregate different traffic types... For example, create separate VLANs for management, replication, and host traffic." This refutes option B.

When sizing for an Oracle Online Analytical Processing (OLAP) workload without specific customer I/O data, the Dell Sizer tool applies a default profile that reflects typical data warehouse and business intelligence operations. This profile is characterized by a high percentage of read operations (70%) due to the nature of complex queries, aggregations, and reporting. The I/O pattern is predominantly random, representing index-driven lookups and non-contiguous data retrieval from large fact tables. The 8 KiB block size is selected as it is the standard and most common default block size for Oracle databases. This combination provides a reliable baseline for initial system design.

A. This is incorrect because OLAP queries, while sometimes involving full table scans (sequential), are more accurately modeled with a random I/O pattern as a default to account for complex joins and index usage.

C. This is incorrect for the same reason as option A; it wrongly assumes a default sequential I/O pattern for a general OLAP workload, which is not the standard baseline in the sizer.

D. This is incorrect because a 50/50 read/write ratio is more characteristic of an Online Transaction Processing (OLTP) or mixed workload, not a read-intensive OLAP environment. The 32 KiB block size is also not the standard default.

1. Dell EMC Unity: Oracle Database Best Practices (Technical White Paper H15343.4, April 2020):

Page 13, Table 3 "Typical Oracle I/O characteristics": This table provides guidance for sizing Oracle workloads. For OLAP/DSS, it specifies a Read % of 70-80%, a Write % of 20-30%, a Random % of 80%, and a typical I/O size of 8 KB–128 KB. The default sizer profile of 70% Random Read and 30% Random Write at 8 KiB aligns directly with the lower end of the I/O size range and the specified ratios for a random OLAP workload.

2. Dell PowerMax and VMAX All Flash: Oracle Database Best Practices and Sizing Guide (Technical White Paper, August 2022):

Section 4.1.1, "Workload characterization": This section discusses the I/O profiles for different Oracle workloads. It describes OLAP as being dominated by read operations with varying I/O sizes, often starting from the database block size (commonly 8 KB). The sizer's default of 70% read, 30% write, and random access at 8 KB is a direct implementation of this characterization for a baseline scenario.

The Dell PowerStore sizing tool uses different default Data Reduction Ratio (DRR) values for block and file workloads to provide a more realistic initial capacity estimate. Block-based workloads, such as virtual machines and databases, typically exhibit high data redundancy and are excellent candidates for deduplication and compression, hence the tool's default of 4:1. Conversely, file-based workloads often contain a mix of data types, including pre-compressed files (e.g., images, videos), which offer less potential for reduction. Therefore, the sizing tool applies a more conservative default of 2:1 for file workloads. These values serve as a starting baseline for sizing calculations.

A. Block = 4:1 File = 4:1: This is incorrect because the sizing tool uses a more conservative default DRR for file workloads due to their varied and often pre-compressed nature.

C. Block = 1:1 File = 1:1: This is incorrect as it implies no data reduction by default, which contradicts the "always-on" data reduction architecture of PowerStore and the purpose of the sizing tool.

D. Block = 2:1 File = 2:1: This is incorrect because the default value for block workloads is higher (4:1) to reflect the greater data reduction efficiency typically seen with structured block data.

1. Dell PowerStore: Sizer Best Practices Guide. (This document is typically available to Dell partners and employees). The guide specifies the default workload parameters used within the tool. In the section covering workload inputs, it states the default DRR for block is 4:1 and for file is 2:1.

2. Dell PowerStore: Data Efficiencies White Paper. This document explains the underlying technology and expected outcomes. In the section "Data Reduction," it details how different data types affect reduction rates, supporting the rationale for using different default values for block (highly reducible) versus file (less predictable) in planning tools. (Reference: Page 9, "Data reduction results").

Dell's best practice is to schedule the FAST VP relocation window during periods of low I/O activity. Specifically, it should be scheduled to run before other I/O-intensive operations like backups or large batch jobs. This strategy serves two purposes: first, it avoids resource contention on the storage array, which would degrade performance if both processes ran concurrently. Second, it ensures that data is optimally placed on the appropriate storage tier prior to the start of these critical jobs, which can improve the performance of the backups or batch processing themselves.

B. During backups or nightly batch processing: This creates severe I/O contention, as both relocation and the batch job are resource-intensive, leading to significant performance degradation for both operations.

C. After backups or nightly batch processing: While this avoids I/O contention, it is not the primary recommendation. Running relocation before allows the batch job to benefit from the optimized data placement.

D. Before and After backups or nightly batch processing: This is inefficient and unnecessary. A single, well-timed relocation window is sufficient and consumes fewer system resources than running the process twice.

1. EMC FAST VP for EMC Symmetrix VMAX Theory and Best Practices for Planning and Performance (White Paper h8058.4), Page 31, Section: "Relocation Window". The document states, "The relocation window should be scheduled during off-peak hours. It is a best practice to schedule the relocation window to occur before other I/O-intensive batch operations, such as backups."

2. Dell EMC Unity: FAST Technology (White Paper H15084.5), Page 11, Section: "Data Relocation". This document reinforces the core principle, stating, "It is also a good practice to schedule data relocation to occur at a different time than other system-intensive operations, such as backups or remote replication synchronizations." This supports avoiding option B.

Enabling data reduction on a Dell Unity XT system, especially on storage resources that already contain data, initiates a background process that consumes system resources, primarily CPU cycles. To avoid performance degradation for existing production workloads, it is a documented best practice to enable this feature during periods of low system activity. A CPU utilization at or below 50% is a clear indicator of low activity, ensuring that the system has adequate processing power to handle both the data reduction process and ongoing host I/O without significant performance impact.

A. CPU utilization above 80% is incorrect. Enabling a CPU-intensive process like data reduction on a heavily utilized system would severely degrade performance and is strongly discouraged.

B. Free capacity above 80% is incorrect. While ample free space is generally good, the primary consideration for enabling data reduction is performance impact, not the amount of free capacity.

C. Free capacity at or less than 50% is incorrect. This condition describes a reason one might want to use data reduction, but it is not the recommended system state for enabling it.

1. Dell Unity: Data Reduction, White Paper (H15923.6, April 2022).

Page 11, Section: Enabling Data Reduction: "It is recommended to enable data reduction during a period of low system activity. This is because enabling data reduction on a LUN or file system with existing data will cause a background process to run which reduces the data. This background process consumes system resources, so it is best to run it when the system is not busy servicing host I/O."

2. Dell Unity XT Series Best Practices Guide (H18149.4, August 2022).

Page 28, Section: Data Reduction: "It is recommended to enable data reduction during a period of low I/O activity. Enabling data reduction on a LUN or file system with existing data starts a background process to reduce the data. This background process consumes system resources, so it is best to run it when the system is not busy servicing host I/O."

The SAS (Serial Attached SCSI) ports on Dell Unity XT storage processors (SPs) are dedicated to back-end connectivity. Their primary and essential function is to create the data path between the SPs and the Disk Array Enclosures (DAEs) or Drive Enclosures. This connection is used exclusively for moving data to and from the physical drives (SSDs, SAS, or NL-SAS) housed within these enclosures for all read and write operations. This back-end SAS network is critical for the storage system's fundamental operation of storing and retrieving data.

B. To provide host connectivity.

Incorrect. Host (front-end) connectivity on Dell Unity XT is provided through dedicated Fibre Channel, iSCSI, or File I/O modules, not the onboard back-end SAS ports.

C. To increase processing speed.

Incorrect. SAS ports are for data I/O and do not directly impact the computational or processing speed of the storage processor's CPUs.

D. To move data between the data array.

Incorrect. This statement is imprecise. The SAS ports specifically connect the controllers (SPs) to the drive enclosures, which is more accurately described as moving data to and from the drives.

1. Dell Unity XT Series Hardware Information Guide (August 2022)

Page 15, "Storage Processor (SP) rear view": The diagrams for various Unity XT models (e.g., 380/F, 480/F) explicitly label the onboard mini-SAS HD ports as "12-Gb/s SAS ports (for back-end connectivity)" and show them connecting to DAEs.

Page 21, "Back-end (SAS) connectivity": This section states, "The storage system uses 12-Gb/s x4 SAS internal ports for back-end connectivity. These ports are used to connect the SPs to the DAEs."

2. Dell Unity: Introduction to the Platform - A Detailed Review (August 2020)

Page 10, "Hardware Overview > Back-End Connectivity": This document details the architecture, stating: "The back-end connectivity for Dell Unity systems utilizes 12Gb/s SAS. The SPs in the DPE each contain two 12Gb/s x4 SAS ports for connecting to DAEs." This confirms the exclusive use of SAS for the SP-to-drive enclosure connection.

According to Dell's official best practices for Unity XT hybrid arrays, the recommended minimum amount of Flash capacity for a hybrid pool is 10%. This recommendation ensures that the FAST VP (Fully Automated Storage Tiering for Virtual Pools) feature has a sufficiently large high-performance tier to store the most active data, or "hot" data. The Dell Sizer tool, including the System Designer option, is built upon these best practices to guide architects in creating balanced and performant configurations. Allocating at least 10% to the Flash tier provides a strong starting point for performance in most mixed-workload environments.

A. 5%: While 5% might be considered an absolute bare minimum in some older contexts, the current and official Dell best practice recommendation is higher to ensure better performance.

C. 15%: This percentage is greater than the recommended minimum. While adding more flash can improve performance, it is not the baseline recommendation for initial system design.

D. 7%: This is not a standard value cited in Dell's best practice documentation for Unity XT hybrid pool design.

1. Dell Unity: Best Practices Guide (H15163.8), Page 21, Section: "Hybrid pools". The document states, "For hybrid pools, it is a best practice to configure at least 10% of the pool capacity as Flash. This provides a large enough tier to accommodate frequently accessed data."

2. Dell Unity: Dynamic Pools White Paper (H15200.4), Page 10, Section: "Best Practices". The paper states, "As a best practice, Dell Technologies recommends configuring at least 10% of the pool capacity as Flash drives."

3. Dell Unity: FAST Technology Overview White Paper (H15084.5), Page 9, Section: "FAST VP Best Practices". The document notes, "As a general best practice, it is recommended to start with 5-10% of Flash capacity in a hybrid pool." The 10% figure represents the more robust and commonly cited recommendation for optimal design.

The PowerStore 5200T is a versatile appliance that supports capacity expansion through the addition of expansion enclosures. This allows for scaling storage capacity beyond the base enclosure.

In a PowerStore T system configured with a mix of Storage Class Memory (SCM) and standard SSD drives, the SCM drives are automatically configured as a dedicated metadata tier. This configuration leverages the extremely low latency of SCM to accelerate system-level metadata operations, enhancing overall appliance performance. Because this tier is reserved exclusively for metadata, its capacity is not included in the total usable capacity available for user data.

B. NVMe drives are not used for Caching and Vaulting.

This is incorrect. While dedicated NVRAM modules handle write caching, the cache content is vaulted (written for protection) to the first four data drives in the base enclosure during a power failure. These drives can be NVMe SCMs.

C. SSD drives are used for metadata tiering.

This is incorrect. In a mixed SCM and SSD configuration, the higher-performance SCM drives are automatically used for the metadata tier to maximize system responsiveness, not the slower SSDs.

1. Dell PowerStore: Introduction to the Platform (White Paper), April 2024.

Reference for Correct Answer D: Page 20, Section "SCM as metadata tier": "When SCM and SSD drives are mixed in a PowerStore T appliance, the SCM drives are used as a metadata tier... The SCM drives do not contribute to the overall user capacity of the appliance."

Reference for Incorrect Option C: Page 20, Section "SCM as metadata tier": This section explicitly states SCM drives are used for metadata, which contradicts the claim that SSDs are used for this purpose.

2. Dell PowerStore Hardware Information Guide, March 2024.

Reference for Correct Answer A: Page 11, Table 3 "PowerStore models specifications": The table indicates that the PowerStore 5200T model supports a maximum of three 2U expansion enclosures.

3. Dell PowerStore: Best Practices Guide, April 2024.

Reference for Incorrect Option B: Page 11, Section "System Drives": "The first four drives in the base enclosure are system drives... These drives are also used as a vaulting area for the write cache in the event of a power failure." This confirms data drives, which can be NVMe, are used for vaulting.

An automatic NAS server failover is a high-availability (HA) function triggered by an unplanned, critical event. If the Storage Processor (SP) that owns a NAS Server experiences a catastrophic hardware fault (e.g., CPU, memory, or power failure) or becomes non-responsive, the system automatically initiates a failover. This process transfers the ownership and operational control of the NAS Server and its associated file systems to the peer SP. This ensures service continuity for connected clients with minimal interruption. This fault-driven, reactive process is distinct from planned administrative actions like migrations or resource balancing.

A. Assisted internal migration: This is a planned, administrator-initiated process for moving resources for maintenance or upgrades, not an automatic failover due to a fault.

B. Network link failure: Dell storage systems use technologies like Link Aggregation and Fail-Safe Networking to provide redundancy, handling individual link failures without requiring a full NAS server failover.

D. Resource balancing algorithm: This describes a proactive, non-disruptive process for optimizing performance across SPs, which is fundamentally different from a reactive failover caused by a hardware failure.

1. Dell EMC Unity: High Availability - A Detailed Review (White Paper), April 2022.

Page 13, Section "NAS Server High Availability": "If the SP that owns the NAS Server fails, the NAS Server automatically fails over to the peer SP. The peer SP takes ownership of the network interfaces and file systems of the failed NAS Server and continues to serve I/O to clients." This directly confirms that an SP failure (a hardware fault) triggers the automatic failover.

2. Dell EMC Unity XT: Unisphere Overview (White Paper), August 2022.

Page 10, Section "High availability": "The Unity XT family is designed for five 9s (99.999%) availability. This is achieved through redundant components such as dual Storage Processors (SPs) in an active/active configuration... In the event of an SP failure, the peer SP takes over and provides access to data." This reinforces that SP failure is the primary trigger for the HA takeover mechanism.

Dell Unity XT asynchronous replication for block resources can be configured using a built-in periodic timer or by associating the replication session with a snapshot schedule. While the built-in timer has a maximum Recovery Point Objective (RPO) of 24 hours, a greater RPO can be achieved by using a snapshot schedule to trigger the replication sync. The snapshot schedule allows for a recurring hourly interval to be set. The maximum value for this recurring interval is 168 hours, which is equivalent to 7 days. Therefore, the maximum configurable interval-based RPO for a block-asynchronous replication session is 7 days.

A. 24 hours

This is the maximum RPO when using the replication session's native periodic timer, but it is not the overall maximum possible when using a snapshot schedule to control synchronization.

B. 14 days

While a calendar-based schedule could be created to run bi-weekly, the maximum configurable interval for a snapshot schedule is 168 hours (7 days), which represents the highest defined RPO frequency.

D. 48 hours

This is a valid RPO that can be configured using a snapshot schedule (e.g., "repeat every 48 hours"), but it is not the maximum configurable value.

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1. Dell Unity Family Unisphere Command Line Interface User Guide (Version 5.2)

Reference: Page 218, create -snapSchedule command description.

Quote/Content: In the description for the -repeatEvery parameter, the guide specifies the valid range for an hourly schedule: "For hours, specify a value from 1 to 168." (168 hours = 7 days). This confirms the maximum configurable hourly interval for a snapshot schedule.

2. Dell White Paper: Dell Unity: Replication Technologies

Reference: Page 16, Section "Asynchronous Replication".

Quote/Content: "It is also possible to use snapshot schedules to trigger synchronization. When a snapshot schedule is used, a new snapshot is created based on the schedule, and this snapshot is replicated to the destination." This document confirms that snapshot schedules are a valid method for controlling asynchronous replication sessions, thereby making their limits applicable to the session's effective RPO.

The supportshow command is the standard and primary command used on Brocade switches running Fabric OS (FOS) to gather and display a comprehensive set of diagnostic data. This output includes switch status, configuration parameters, port statistics, error logs, and other system information. The collected data is essential for troubleshooting and is typically requested by technical support for analysis. The command consolidates the output of numerous other individual show commands into a single, extensive report.

A. show all: This is not a valid command in Brocade Fabric OS. The show command requires a specific argument (e.g., show switch, show port) and does not have an all option.

B. show tech-support details: This command syntax is not used in Brocade Fabric OS. It is more characteristic of other networking vendors, such as Cisco, for gathering support information.

1. Dell EMC Connectrix B-Series Fabric OS 8.2.1 Command Reference Manual:

Page 789, Chapter 4 "Command Pages": Describes the supportshow command: "Use the supportshow command to display a large amount of information about the switch and its attached devices. This command is intended for use by your support provider for problem diagnosis." This manual does not list show all or show tech-support details as valid commands.

2. Broadcom Inc., Brocade Fabric OS Command Reference Manual, 9.0.x:

Page 1001, "supportshow" section: "The supportshow command gathers output from many commands, such as switchshow, ipaddrshow, configshow, portshow, and errdump, and displays the information on the screen." This confirms its function as a data-gathering tool for support purposes.

The formula VM count Capacity per VM is a standard sizing calculation used to determine the total logical capacity required by a specific workload, in this case, a set of virtual machines. In Dell PowerStore terminology, this logical capacity is provisioned from the Usable Capacity. Usable Capacity represents the total space available for data storage after system overhead and RAID protection are accounted for, but before any data reduction technologies (like compression and deduplication) are applied. Therefore, the result of this calculation is the amount of usable capacity that must be allocated for the VMs.

B. Raw Capacity: This is the total, unformatted physical capacity of all drives in the system. It does not account for RAID overhead or system space and is not what is allocated to hosts.

C. Effective Capacity: This refers to the total amount of host data that can be stored after applying data reduction. The calculation represents the data size before reduction is considered.

1. Dell Technologies White Paper: Dell PowerStore: Introduction to the Platform

Page 11, "Capacity" section: Defines the capacity terms. It states, "Usable capacity is the total capacity available for data storage after system overhead and data protection (RAID) are configured. This is the capacity available to the user before data reduction." This directly supports that the pre-reduction workload size (VM count Capacity per VM) corresponds to the Usable Capacity metric.

2. Dell Technologies White Paper: Dell PowerStore: Data Efficiencies

Page 5, "Terminology" section: Differentiates between Logical Size, Usable Capacity, and Physical Capacity. It clarifies that "Logical size is the amount of data that the host has written to a storage resource before data reduction." The calculation in the question determines this total logical size, which is provisioned from the system's Usable Capacity.

Dell Unity XT systems are designed with specific software and hardware limitations to ensure optimal performance and stability. The architecture allows for the creation of up to 32 thin clones from a single source resource. This source can be a base LUN, a LUN within a consistency group, or a VMware VMFS datastore. This limit is a fixed value within the Unity OE (Operating Environment) software and applies across the Unity XT family of storage arrays.

A. 12: This number is incorrect and significantly lower than the documented maximum limit for thin clones per source in Dell Unity XT.

C. 16: This value is incorrect. While it represents a power of two, it is not the specified limit for thin clones per base LUN.

D. 24: This is an incorrect value that does not align with the official configuration maximums published by Dell for the Unity XT platform.

1. Dell Technologies. (2020). Dell Unity: Snapshots and Thin Clones White Paper. Page 18, Section: "Thin Clones". The document states, "A base LUN, consistency group LUN, or VMware VMFS datastore can have up to 32 thin clones."

2. Dell Technologies. (2022). Dell Unity XT Family Specification Sheet. Page 2, Table: "Software". The row "Max. thin clones per source" lists the value as "32".