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Dell Midrange Storage Solutions Design 2023 > Midrange Storage Performance Planning: Data Services and Array Features > Flashcards

Midrange Storage Performance Planning: Data Services and Array Features Flashcards

1
Q

What models is FAST VP supported on Unity XT?

A

Unity HFA

UnityVSA

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2
Q

What is FAST VP?

A

fully automated storage tiering for virtual pools

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3
Q

What is the advantage of using mixed pools in Unity HFA?

A

reducing cost of configuration by reducing drive counts and using large capacity drives

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4
Q

What are tiering policies in FAST VP?

A

determine how the data relocation takes place within a storage pool

access patterns for all data within a pool are compared against each other

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5
Q

What is the Highest Available Tier policy in FAST VP?

A

when quick responses are a priority

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6
Q

What is the Auto Tier policy in FAST VP?

A

automatically relocates data to the most appropriate tier based on the activity level of each slice

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7
Q

What is the Start High, Then Auto Tier policy in FAST VP?

A

recommended policy for each newly created pool

takes advantage of Highest Available and Auto tier policies

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8
Q

What is the Lowest Available Tier policy in FAST VP?

A

when cost effectiveness is highest priority

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9
Q

What is the default policy in FAST VP?

A

Start High Then Auto Tier

places initial allocation of objects in highest tier available - monitors activity of the object to determine correct placement

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10
Q

How does the tiering process in FAST VP work?

A

tracks data in a storage pool per slice (256MB)

ranks slices according to level of activity - automated

most utilized data is on hot tier

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11
Q

How does FAST VP help with Unity XT performance?

A

automatically moves data within a pool to appropriate drive technology

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12
Q

When is FAST VP most effective for Unity XT?

A

if data relocation occurs during or immediately after normal daily processing

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13
Q

How should you configure FAST VP for highly active applications?

A

for relocation to run constantly

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14
Q

What is the appropriate free capacity for FAST VP to work correctly?

A

recommended at least 10% free capacity in storage pools so relocation can occur efficiently

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15
Q

What’s the main benefit of FAST Cache?

A

can scale up to a larger than the maximum DRAM Cache capacity

improves the access of data that is resident in the SAS and NL SAS layers

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16
Q

What does FAST Cache consist of?

A

one or more RAID 1 pairs of SAS flash 2 drives

provides both read/write caching

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17
Q

What process does FAST Cache do during reads?

A

driver copies data off the disk being accessed in FAST Cache

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18
Q

What process does FAST Cache do during writes?

A

effectively buffers the data waiting to be written to disk

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19
Q

How does FAST Cache work?

A

identifies a 64KB chunk of data that is accessed frequently

system then temporarily copies data to FAST Cache

storage services further requests faster since its pulling it from FAST Cache now

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20
Q

What is the performance benefit of FAST Cache?

A

reduces the load on the underlying disks of the LUNs that will ultimately contain data

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21
Q

What happens when data sitting in FAST Cache gets less frequently accessed?

A

data is flushed out of cache

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22
Q

What is the FAST Cache policy engine?

A

software that monitors and manages the IO flow through FAST Cache

keeps statistics to determine what data is good for promotion

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23
Q

When does data become eligible for promotion to FAST Cache?

A

when an eligible block is accessed from spinning drives three times within a short period of time

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24
Q

How are the FAST Cache policies defined?

A

system defined and can’t be modified by the user

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25
Q

What is the FAST Cache memory map?

A

contains information about all the 64KB blocks currently residing in FAST Cache

each time promotion/demotion occurs map is updated

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26
Q

Where is the FAST Cache memory map located in Unity XT?

A

resides in DRAM memory and system drives

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27
Q

How does the FAST Cache memory map work?

A

when FAST Cache is enabled SP memory is allocated to the memory map

when an IO reaches FAST Cache the memory map is checked

IO either redirected to a location in FAST Cache or the pool

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28
Q

What is a FAST Cache flush?

A

process where FAST Cache page is copied to HDDs and page is freed for use

Least Recently Used algorithm used to determine what can be flushed to make room

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29
Q

What is FAST Cache cleaning?

A

proactively copies dirty pages to underlying physical drives during times of minimal backend activity

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30
Q

What is each RAID 1 pair in FAST Cache called?

A

FAST Cache object

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31
Q

How do you expand FAST Cache?

A

in pairs - can do it up to the system maximum

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32
Q

What is a FAST Cache shrink operation?

A

allows the removal of all but 2 drives from FAST Cache

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33
Q

What is the performance benefit of FAST Cache on Unity HFA?

A

can increase the achieveable IOPS of the system

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34
Q

What is a result of higher IOPS potential from FAST Cache on Unity HFA?

A

system has higher CPU utilization since additional IO must be serviced

why you should monitor current utilization before enabling

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35
Q

What should an admin do before configuring FAST Cache?

A

add a flash tier to the hybrid pool

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36
Q

What workloads would call for FAST Cache utilization in a Unity HFA?

A

if workload is highly transactional and has a high degree of locality that changes rapidly

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37
Q

When is it more beneficial to increase the flash tier in a Unity HFA than use FAST Cache?

A

apps that use larger IO sizes - have low skew - or do not change locality quickly

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38
Q

What type of data reduction does Unity XT have?

A

Inline

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39
Q

Where does data reduction take place in Unity XT?

A

in buffer cache before destaging to disk

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40
Q

What is the logical algorithm on Unity XT data reduction?

A

zero detection and deduplication

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41
Q

When do processor cycles occur on Unity XT?

A

only used for deduplication and compression logic

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42
Q

What is required for data reduction to be enabled on Unity XT?

A

pool must contain a flash tier

total usable capacity of flash tier must meet or exceed 10% of the pool

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43
Q

Where is data reduction supported on Unity XT systems?

A

supported on all thin provisioned resources that are created from All Flash and Hybrid flash pools

affects all incoming writes once enabled

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44
Q

What is advanced deduplication on Unity XT?

A

dynamic deduplication algorithm which reduces storage consumption by eliminating duplicate 8KB blocks within a storage resource

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45
Q

How does advanced deduplication work on Unity?

A

if normal deduplication doesn’t detect a pattern it passes through advanced algorithm

uses fingerprints for all created blocks to quickly identify duplicates within data set

if a block matches an existing cached footprint block is not written and pointer made to original fingerprint

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46
Q

What Unity system doesn’t support data reduction?

A

UnityVSA

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47
Q

What is deduplication?

A

use algorithms to perform pattern detection and store only a single instance of data

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48
Q

What is compression?

A

encodes data using fewer bits than the original representation

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49
Q

What is zero detection?

A

logically detects and discards consecutive zeros - saves only one instance - uses pointers

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50
Q

What is the performance impact of data reduction on Unity XT?

A

increases overall CPU load on the system when reducible data is read/write - may increase latency

make sure system has available resources to perform data reduction

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51
Q

What are the 3 parts of Powerstore data reduction?

A

compression
deduplication
zero detection

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52
Q

At what level does deduplication work in Powerstore?

A

at the block level at 4KB granularity

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53
Q

What happens to Powerstore data reduction during high write activity?

A

may defer the deduplication of data and devote resources to servicing the client workloads

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54
Q

What happens to Powerstore during low activity periods?

A

will use excess resources to re-examine any data written during high write periods for duplicates to regain space savings

55
Q

What are snapshots?

A

point in time copies of block and file resources

56
Q

What are the supported source of snapshots on Unity XT?

A

LUNs
consistency group LUNs
file systems
VMWare VMFS data stores
NFS data stores

57
Q

How are snapshots created on Unity?

A

manually or through a schedule

58
Q

What is the benefit of using Unity snapshots?

A

restoration is instant and does not use extra storage space

59
Q

How are snapshots supported in Unity XT?

A

supported on both physical Unity and UnityVSA

60
Q

What are hierarchical snapshots in Unity XT?

A

snapshots of snapshots

can go 10 levels deep

61
Q

What are snapshots the foundation of in Unity XT?

A

asynchronous replication

62
Q

What is the relationship between LUNs and snapshots in Unity XT?

A

consistency group snapshots apply to all LUNs in the group

restoring a consistency group snapshot means all members are restored

63
Q

What are the performance recommendations when enabling snapshots in Unity XT?

A

include a flash tier in a hybrid pool where snapshots are active

64
Q

What performance impact do snapshots have on Unity XT?

A

increase overall CPU load

increase overall drive IOPS

65
Q

What capacity impact do snapshots have on Unity XT?

A

use pool capacity to store older data being tracked

tracking increases amount of capacity that is used in the pool until the snapshot is deleted

66
Q

What are the operation recommendations for snapshots on Unity XT?

A

schedule snapshots operations after any FAST VP relocation has completed

staggering snapshots operations on different schedules (creation, deletion, etc.)

67
Q

What is a thin clone?

A

read/write copy of a thin block storage resource that shares blocks with the parent resource

68
Q

How do thin clones utilize snapshots in Unity XT?

A

use snapshots to provide space efficient clones for block objects

69
Q

What is a Base LUN family in Unity XT?

A

combination of Base LUN and all its derivative thin clones/snapshots

70
Q

What is a Base LUN in Unity XT?

A

original or production LUN for a set of derivative snapshots and thin clones

71
Q

What platforms are thin clones supported on Unity XT?

A

both physical and UnityVSA

72
Q

How are thin clones created on Unity XT?

A

from attached read only or unattached snapshots with no auto-deletion policy and no expiration policy set

73
Q

How do thin clones effect performance on Unity XT?

A

based on pointer based technology - does not consume much space in the storage pool

share space with base resource rather than allocate a copy of the source data for itself

74
Q

What is the performance recommendation for Unity XT when implementing thin clones?

A

including flash tier in a hybrid pool where thin clones are active

75
Q

What is data availability with thin clones on Unity XT?

A

data on source snapshot immediately available to thin clone

data resulting from changes to thin clone after its creation is stored on the thin clone

76
Q

What are the supported storage resources for snapshots on Powerstore?

A

volume

volume group

virtual machines

file system

77
Q

What are the supported storage resources for thin clones on Powerstore?

A

NAS Server

file system

file system snapshot

volume

volume group

78
Q

What is important to know about volume snapshots on Powerstore?

A

volume snapshots are read only

cannot add to - delete from - change contents of volume snapshots

79
Q

What is important to know about file system snapshots on Powerstore?

A

can be refreshed

80
Q

How do you access a snapshot on Powerstore?

A

hosts or NAS clients have no direct access

to access data clone the snapshot

for a clone of a volume snapshot - map it to a host

for a clone of a file system snapshot - create an NFS export or SMB share

81
Q

What is the performance impact of thin clones and snapshots on Powerstore?

A

all storage resources are thin provisioned including snaps and clones

creation of snap/clone requires only quick duplication of pointers

than act as independent resources and don’t pull from performance of source

82
Q

What is asynchronous replication mostly used for?

A

replicate data over long distances

83
Q

What performance impact does asynchronous replication have on Unity XT?

A

does not impact host IO latency

host writes are acknowledged after they are saved to local storage resource

writes not immediately replicated to destination resource

84
Q

How do remote and local systems communicate in asynchronous replication on Unity XT?

A

formed from replication interfaces

IP based connections established on each system

85
Q

How is the replication session managed in asynchronous replication?

A

communication channel required

management channel established on a Replication Connection

channel defines management interfaces and credentials for each system

86
Q

What are the minimum and maximum configurable RPO on Unity XT asynchronous replication?

A

5 minutes - 1440 minutes (24 hours)

87
Q

How is local replication performed on Unity XT?

A

asynchronously within the same storage system

storage resources are replicated from one storage pool to another

88
Q

How does local replication on Unity XT incorporate snapshots?

A

uses snapshots on both source and destination pools to track changes and data transfers

helpful if storage must be moved due to pool capacity reasons or when changing the type of storage the resources uses

89
Q

What storage resources are supported for local replication?

A

LUNs/Consistency Groups

thin clones

VMWare VMFS/NFS data stores

NAS Servers/file systems

90
Q

What are the performance recommendations for Unity XT asynchronous replication?

A

include flash tier in hybrid pool - creates flash tier on both source and desitination

configure multiple replication interfaces per SP/distribute sessions across thme

configure LACP for bandwidth concerns with jumbo frames

91
Q

How should you configure RPO on replication sessions in Unity XT?

A

avoid setting smaller RPO values - result in more snapshot operations + do not make replication sessions transfer data more quickly

choosing larger RPOs/manually synchronizing may provide more predictable performance

92
Q

Why should you fill a storage object with data before creating a replication session from it on Unity XT?

A

fastest way to populate the destination storage

93
Q

What is synchronous replication?

A

ensures that each block of data that is written is saved to the local and remote systems before the write is acknowledged to the host

94
Q

What is the performance effect of synchronous replication?

A

since each write must be saved locally and remotely added response time occurs during each transaction

response time increases as distance increases between remote images

95
Q

What is the advantage of synchronous replication?

A

ensures zero RPO between the local and replica

96
Q

How is synchronous replication run on Unity XT?

A

uses write intent logs (WIL) on each of the systems

97
Q

What do WILs do in synchronous replication on Unity XT?

A

hold fracture logs that are designed to track changes to the source storage resource should the destination storage become unreachable

when destination becomes reachable again synchronization automatically recovers using the fracture log

98
Q

What is the distance limitation on synchronous replication in Unity XT?

A

generally 60 mi (100km) between sites

99
Q

What is the recommended latency between systems in synchronous replication with Unity XT?

A

less than 10 milliseconds

100
Q

How is a synchronous replication connection established on Unity XT?

A

data connection through FC

communication channel required to manage replication sessions

part of management provided using Replication Interfaces

101
Q

What is the perfomance recommendation when performing synchronous replication on Unity XT?

A

include a Flash tier in a hybrid pool - applies to both source and destination pools

102
Q

How is data transferred in synchronous replication in a Unity XT?

A

transfers data to the remote system over the first FC port on each SP

want to reduce number of host connections to this port if wanting to perform synchronous replication

103
Q

Why should you create the synchronous replication session first before filling the source storage in Unity XT?

A

filling source object alleviates need to perform initial synchronization of the replication session

fastest way to populate destination session object w/ synchronous replication

104
Q

On what Unity systems are replication sessions available?

A

only on physical systems

105
Q

What does Unity XT file remote protection support?

A

combination of synchronous and asynchronous remote replication sessions together

106
Q

What is the encryption method in Unity XT?

A

controller based D@RE

uses hardware that is embedded in all SAS IO modules and SPs

107
Q

What performance impact does D@RE have on Unity XT?

A

encryption and decryption occur with minimal impact on data services like replication/deduplication

108
Q

What is the advantage of D@RE over SEDs?

A

simple, lower cost, and more maintainable

drive vendor/type agnostic - eliminates drive specific vendor overhead

109
Q

How does D@RE protect data?

A

provides protection against data being read from a lost, stolen, or failed disk drive

encrypted using 256-bit AES algorithm

based on FIPS-140-2 validation

110
Q

What is external key management on D@RE?

A

data is protected from access if the storage system is stolen or while a planned relocation to a different site is happening

111
Q

What are the encryption recommendations for Unity XT?

A

recommends ordering with encryption enabled - can only be enabled at time of system installation with appropriate license

112
Q

What happens when encryption is enabled in Unity XT?

A

internal key manager generates and manages encryption keys

recommend making external backup of these keys

113
Q

How do you decommission a Unity XT?

A

deleting pools

deletes all drive encryption keys and eliminates the necessity to shred disk drives

114
Q

What does Powerstore D@RE protect from?

A

stolen drives

during transit

discarded drives

115
Q

What are the components required for Powerstore encryption?

A

SEDs

Key Management Service (KMS)

116
Q

What is required to keep encryption on Powerstore after adding or removing a drive?

A

keystore file must be backed up

if KMS fails or keystore file cannot be read encrypted data can’t be accessed

117
Q

When is Powerstore encryption enabled?

A

automatically activated during the initial configuration of the system

118
Q

What is important about scalability with Powerstore encryption?

A

adding non-SED drives to an appliance is not supported

adding an unencrypted appliance to an encrypted cluster is not supported

119
Q

What is the internal key management for Powerstore encryption?

A

uses an embedded KMS that resides in the Base System Container of the active node of each appliance

all keys are aggregated to the primary appliance in a cluster

120
Q

What is the Host IO Limits feature on Unity XT?

A

limits initiator IO operations to the block storage resources

can be set on physical or virtual deployments of Unity

121
Q

When are Host IO limits active in Unity XT?

A

when policies are created and assigned to the storage resources - provides system wide pause and resume controls

122
Q

What are the Host IO limit policies in Unity XT?

A

customizable for absolute IOs, density based IOs, and burst IOs

can set limits by throughput in IOPS, bandwidth in KBPS/MBPS, combination of both limits

123
Q

What are the limits on the Host IO Limit feature?

A

only one IO limit policy can be applied to an individual LUN or a LUN that is a member of a consistency group

124
Q

What if both the throughput and bandwidth limits are in place for Host IO Limits in Unity?

A

system limits the traffic according to the threshold that is reached first

125
Q

What are the performance recommendations for implementing Host IO Limits in Unity XT?

A

setting them on workloads which may monopolize pool resources and starve other resources of performance

Large block applications that monopolize IO

small block applications get starved for access

126
Q

Why may it be beneficial to implement Host IO Limits on snapshots in Unity?

A

applicable to attached snapshots which are being used for backup/testing purposes

can be applied to snapshots to prioritize host activity towards the parent LUNs and datastores

127
Q

What is the configuration recommendation for provisioning file storage on an ESXi host on Unity XT?

A

create VMWare NFS Datastores instead of general purpose NFS file systems

optimized to provide better performance with ESXi

128
Q

How show VMWare NFS Datastores be configured on Unity XT?

A

use the default 8K host IO size

only choose different host IO size if all applications that are hosted in the NFS Datastore primarily use the selected IO size

129
Q

How show vVol (File) Datastores be configured on Unity XT?

A

create at least two vVol-enabled NAS Servers for each SP

130
Q

What are the configuration recommendations to optimize performance for Powerstore X?

A

create additional internal iSCSI targets

increase internal iSCSI queue depths

enable jumbo frames

131
Q

What do Dell Unity systems require to deliver the maximum IOPS?

A

high concurrency

naturally achieved when connecting many hosts with many LUNs and having multiple active paths to the same storage object

for smaller environments host HBA settings may need to be adjusted to increase concurrency

132
Q

When should you use thick storage objects on Unity XT?

A

for workloads that require high bandwidth for sequential streaming data

133
Q

Why woudl thick storage objects be recommended for sequential streaming workloads?

A

thick objects fully allocate capacity before application use and in a consistent manner - can improve subsequent sequential access

134
Q

What features are thick objects not compatible with on Unity XT?

A

data reduction

snapshots

asynchronous replication

Dell Midrange Storage Solutions Design 2023 (18 decks)

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