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Dell SPEED Guru Exams > SPEED Unity Exam > Flashcards

SPEED Unity Exam Flashcards

1
Q

When adding new drives and disk access enclosures (DAEs) to a Unity system, which method will yield greater performance?

A

Cable 1 DAE on each available bus and then distribute additional DAEs evenly; evenly distribute flash drives across all busses

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2
Q

How much parity information will be written to the drives on a 1 MB aligned write to a RAID 6 4+2 LUN?

A

(64KB)

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3
Q

What is a primary purpose of the Unity CMI channel?

A

Mirroring of write operations

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4
Q

A customer has requested an all FLASH solution for their block storage and expects their load capacity to grow to 35 TB in the next 5 years. They want to minimize additional drive load due to possible metadata activity. Which system should be recommended as a solution for the customer?

A

U450F

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5
Q

What accurately describes “skew” in respect to storage systems?

A

Measure of the non-uniformity of data access to different address regions of storage capacity

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6
Q

If there are 20 drives In a RAID 1/0 striped mirror configuration, what is the maximum number of drives that could fail and still maintain data access?

A

10 drives if that left 1 from each pair available

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7
Q

What is a recommended way to ensure a Unity system is capable of supporting Snapshots?

A

Plan enough drives to support the additional I/O for Snapshots, in addition to the customer’s expected workload

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8
Q

Approximately how much initial allocated capacity is used for a new Thin LUN on a Unity system?

A

(1.5GB)

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9
Q

What is a benefit of performing prefetch?

A

Improves response time for sequential I/O reads

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10
Q

What is an advantage of ALUA in a Unity system?

A

(Active/Active LUN access, with load balancing across both SPs)

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11
Q

What is the stripe element size for Unity RAID 5 storage pools?

A

(256KB)

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12
Q

What accurately describes the performance impact to production workloads while a RAID 5 RAID Group is rebuilding after a drive failure?

A

(Severe, as the storage must read 1 piece of data from all remaining RAID Group members, read 1 piece of parity from all remaining RAID Group members, calculate the new data and parity, and write the new data and parity to the hot spare drive)

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13
Q

A customer has unused Flash drives in a Unity All-Flash system, and would like to create a new dynamic pool. They want to combine 15x SAS Flash 3 and 10x SAS Flash 4 into a dynamic pool, with RAID 5 protection. What should be the appropriate response to the customer?

A

(Since there are more than 13 total drives, the largest RAID 5 stripe width of 12+1 will be applied to the pool)

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14
Q

When expanding a Unity traditional pool, what is the preferred number of drives that should be added to any single tier?

A

A multiple of the preferred RAID modulus drive count for that tier

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15
Q

A customer is purchasing a Unity system that will host an application requiring high read and write bandwidth. Clients will connect through iSCSI. In addition to determining the appropriate model and drive complement, which two (2) options should be considered?

A

Determine if the SAS I/O Module will be required to meet the application bandwidth

Determine the appropriate number and type of network ports required to meet the application bandwidth

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16
Q

Which three (3) options accurately describe how Unity detects workload skew and optimizes for best performance?

A

MCC tracks cache activity and keeps most recently used data in DRAM

FAST VP calculates relative temperature for all slices in a storage pool, and moves the hottest slices to the highest-performing tier

FAST Cache tracks accesses to drive elements, identifies HDD regions that are frequently re-hit, and promotes them to Flash drives

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17
Q

What is the I/O size used to transfer data between a Unity NAS server and storage processor?

A

(Always 8 KB)

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18
Q

In block synchronous replication with Unity, what is the process for a host read?

A

(Data is verified to be consistent between the local and remote LUNs before sending the data to the host)

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19
Q

What is required to retrieve performance archives from a Unity system?

A

(Archive to CSV dump utility)

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20
Q

A customer has requested the appropriate Unity cache tunings for their File-based backup-to-disk solution. Which tuning should be recommended?

A

(Set write cache size to be twice the value of buffer cache size; give any remaining DRAM to read cache)

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21
Q

For cached sequential writes, what is the performance difference between RAID 5 and RAID 6 with the same number of effective drives?

A

(RAID 5 is faster no matter what)

22
Q

How is the workload balanced across the 2 SPs in a Unity system?

A

Primary assignment of multiple LUNs and file systems are distributed across the 2 SPs

23
Q

When monitoring performance of a Unity system in real time through UEMCLI, what is the minimum interval that is supported?

A

5 seconds

24
Q

What is the meaning when a data set is said to have skew of 75%?

A

A quarter of the capacity is handling three quarters of the workload

25
Q

Which statement is accurate regarding a Unity all-Flash array?

A

Allocation of new slices considers Flash wear levels and relative activity

26
Q

Which statement is accurate regarding concurrency in a midrange storage system?

A

Greater concurrency can lead to greater performance from storage systems with multiple service centers

27
Q

A customer is considering 4 TB NL-SAS drives for an application with sequential access that requires moderate performance. The customer is sensitive to price, but also wants to avoid restoring data from a backup due to drive failures. Which RAID type should be recommended to address the needs of the customer?

A

(RAID 5)

28
Q

What is a benefit of Flash drives (SSD) over spinning drives (HDD)?

A

Because there are no moving parts, service times for random workloads are much lower with Flash

29
Q

What does a dirty page refer to in a Unity system?

A

A memory page in cache that has valid data which is not yet committed to drive

30
Q

A customer has been using thin LUNs and thin file systems with their Unity system. They plan to enable Data Reduction on their system to improve their capacity utilization. After enabling Data Reduction, how will their performance potential be affected?

A

Less, because the data reduction and re-hydration algorithms consume more CPU and memory resources

31
Q

What is a benefit of using more HDDs in a parity RAID Group?

A

(Improved performance balance across HDDs)

32
Q

When constructing a Unity hybrid (tiered) pool, Dell EMC recommends that at least 5% of the pool’s capacity be in the Extreme Performance (Flash) tier. How will this 5% be used by the pool?

A

The Flash capacity will hold metadata associated with thin LUNs, file systems and snapshots, as well as hot data promoted by FAST VP

33
Q

What is the primary method that Unity storage systems use to improve performance?

A

An intelligent DRAM-based cache which buffers the client from drive latencies, and coalesces I/O for improved drive efficiencies

34
Q

A customer is concerned about high response times from their Unity system. When you look at one week of performance data in the performance dashboard, there is nothing wrong. What should be the recommended response?

A

Discuss with the customer a specific time period of concern and retrieve/analyze archive data for that period

35
Q

Which option does not affect performance?

A

Flash drive seek distance

36
Q

Which three (3) options can the term skew be applied to when considering a Unity system?

A

(520 byte sectors used on all drives
LUN
Sub-LUN 256MB slice used by FAST-VP)

37
Q

What is the definition of storage performance?

A

Being able to meet the requested client workload delivering host-requested IOPS and MBps with acceptable response times under all conditions

38
Q

What is a possible reason for the Unity GUI Performance View showing lower utilization of a storage processor than is seen in performance archive data for the same period?

A

(System was under less load)

39
Q

What is recommended when implementing Unity synchronous replication for Block LUNs?

A

Utilize the highest speed FC link possible

40
Q

What is a recommended method when sizing a Unity system for performance?

A

Use the Midrange Sizer, which incorporates drive and system capabilities

41
Q

In which RAID configuration will a Unity RAID 5 full-stripe-write optimization work?

A

(Any supported RAID group size)

42
Q

Which statement is accurate regarding a small-block random write workload?

A

RAID 1/0 storage requires 2 drive I/Os for every 1 host I/O, RAID 5 requires 4 drive I/Os for 1 host I/O, and RAID 6 requires 6 drive I/Os for every 1 host I/O

43
Q

Which scenario is likely to cause data to be promoted from HDD into Unity FAST Cache?

A

Multiple random cache miss I/Os touch the same tracked region

44
Q

How do Unity models differ, in order to offer higher performance?

A

Higher models use higher CPU core counts, higher density DIMMs

45
Q

Which information is critical in determining storage system configuration for performance?

A

Different drive types and quantities will be needed to meet a certain IOPS load that is random vs. sequential access

46
Q

You have performance data from a previous generation product and want to size a suitable Unity system to accommodate the workload and provide headroom to grow. Which option should be used to accomplish this task?

A

Use the Midrange Sizer Performance Data Input Path which characterizes I/O from input performance data and proposes a solution that can then be manually edited to allow for growth

47
Q

A client application randomly sends 100 I/Os to the storage system. 50% of the I/O is read, and the other 50% is write. The storage is configured with RAID 5 protection. How many drive I/Os should the system issue to the back-end to satisfy this work?

A

250

48
Q

Which three (3) options are preferred reasons to use multiple Unity front-end ports for host connectivity?

A

More active front-end ports increase the IOPS and bandwidth capability between the system and the clients

More active front-end ports improve the multipathing and load-balancing options for clients

More active front-end ports better distribute Block load across the SP CPU cores

49
Q

What is a main differentiator between file system objects and LUN objects?

A

Access protocols for a file system put more burden on the storage system’s resources; LUN access protocols have the least overhead

50
Q

A customer is interested in a Unity All-Flash system, but they want to test the performance before committing to a purchase. You provide them with a Unity 450F, with 19x 800 GB Flash drives. They have made available some idle servers connected to a 1 Gb/s switch. The customer will test with iSCSI protocol, and plans to connect to the network using the 10G Base-T ports on the DPE. What is likely to be the bottleneck in this testing?

A

Network connectivity, because there will only be 4x 1Gb/s connections

Dell SPEED Guru Exams (8 decks)

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