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Dell Midrange Storage Solutions Design 2023 > Unity Whitepapers > Flashcards

Unity Whitepapers Flashcards

1
Q

What are the first 4 drives in Unity?

A

system drives

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2
Q

What are system drives used for in Unity?

A

contain copies of data used by the OS

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3
Q

What are the limitations for Unity system drives?

A

can be used in Pools for user data

cannot be used as traditional hot spare for non-system drive

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4
Q

What is the minimum number of drives in a Unity XT?

A

5

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5
Q

How are system drives configured in Unity XT?

A

RAID 1/0 (2+2)

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6
Q

How many lanes are on the 12Gb SAS ports in Unity XT?

A

4-lane configuration

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7
Q

What is the front-end connectivity on Unity XT 380SPs?

A

2x CNA ports

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8
Q

What are the connectivity options for the CNA ports on Unity 380?

A

16/8/4GB FC
10GbE Optical SFP/TwinAx/1GbE

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9
Q

What is specific about CNA optical connectivity for Unity 380?

A

full iSCSI offload - relieves SP

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10
Q

What does Unity 380 XT have for management connectivity?

A

1GbE BaseT management port
1GbE service port

can be customized to match environment MTU

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11
Q

Where is the DPE connected to on Unity 380 XT ?

A

Bus 0

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12
Q

What is the M.2 drive used for in Unity SPs?

A

serves as backup device in the event of SP failure

memory contents of SP’s cache are written to Mi2 so it can be recovered once SP is restored

also holds boot image to run OS

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13
Q

What happens if their’s an SP and M.2 failure?

A

cache data can be recovered from the peer SP

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14
Q

How many cooling module failures can Unity XT SP handle?

A

single cooling module fault out of 5 per SP

if second module fails the SP will save cache content and shutdown to prevent overheating

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15
Q

What is the BBU in Unity XT?

A

provides power to SP if cabinet power is lost

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16
Q

What is something that is in addition to Unity XT 480 and higher SP models?

A

optional 4 port mezz card

25GbE Optical/10GbE BaseT

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17
Q

How is the DPE connected on Unity XT 480 and higher?

A

Bus 99

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18
Q

How is the first expansion port connected on Unity XT 480?

A

Bus 0

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19
Q

What are power supply options on Unity XT?

A

DC - 380/480
AC - all models

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20
Q

What are the DAE options on Unity XT?

A

25-Drive 2U DAE using 2.5” drives
15-Drive 3U DAE using 3.5” drives
80-Drive 3U DAE using 2.5” drives

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21
Q

What are the capacity options on UnityVSA?

A

10,25,50,350TBs

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22
Q

What is specific about Unity file data?

A

can make unified pool - don’t need to separate it out

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23
Q

What is required in Unity before creating a file system?

A

creation of a NAS Server

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24
Q

What is the makeup of a NAS Server in Unity?

A

each is logically separate - clients of one NAS can’t access data on another

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25
Q

What is true about link aggregation in Unity?

A

same speed
same duplex settings
same MTU size

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26
Q

When is link aggregation not supported on Unity?

A

not supported for iSCSI since multipathing is used for block access

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27
Q

What is fail safe networking (FSN) in Unity?

A

extends link failover into the network by supporting switch level redundancy

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28
Q

What is the relationship between link aggregation and FSN?

A

FSN provides extra layer of protection - link aggregation protects against port failure - FSN protects against full switch failure

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29
Q

What is the range of file system size in Unity?

A

3GBs - 256TBs

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30
Q

What do all thin file systems in Unity have regardless of size?

A

1.5GB reserved for metadata

all file systems in Unity thin by default - can make thick if want to

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31
Q

What is the default block size in Unity XT file systems?

A

8KB

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32
Q

What are the quota limits in Unity XT?

A

Soft limit (GB)
*Grace period (time)
*Hard limit (GB)

when soft limit is reached timer begins - if enough space isn’t reclaimed before timer runs out no new storage can be written to file system

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33
Q

What is 2 way vs 3 way NDMP?

A

2 way = file system backup that transfers data over FC directly to backup device - must use FC switch in between

3 way = file system backup that transfers backup data over network

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34
Q

What is MetroSync on Dell Unity XT?

A

ability to create remote synchronous replication sessions for file storage resources

NAS Servers
file systems
VMWare NFS datastores

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35
Q

What version of Unity doesn’t support synchronous replication?

A

UnityVSA (b/c it doesn’t have FC connectivity - synchronous replication based off first FC port on Unity)

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36
Q

What are the features of MetroSync on UnityXT?

A

snapshot replication
snapshot schedule replication
cabinet level failover
asynchronous replication to a third site

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37
Q

What is the benefit of snapshot schedule replication?

A

ensures destination system has same snapshot schedules applied as the source system in case of failover

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38
Q

What is cabinet level failover?

A

single command to initiate a simultaneous failover of all synchronously replicated NAS Servers and their associated file systems in parallel

should only be used when source system goes down

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39
Q

What can’t synchronous replication be used for in Unity XT?

A

local replication of file systems within same array

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40
Q

When is asynchronous replication used in Unity XT?

A

transporting data over long distances

replicate file resources locally between pools

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41
Q

How is asynchronous replication supported on Unity XT?

A

for file and block workloads and every model

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42
Q

What types of asynchronous replication are available on Unity XT?

A

one directional
fan-out
cascade
mixed

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43
Q

What is one-directional replication?

A

single resource replicating to a single destination resource

A →B

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44
Q

What is fan-out replication?

A

single resource replicating to up to four different destination systems

A →B and A →C

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45
Q

What is cascade replication?

A

single resource replicating to second system and from there replicating to a third system

A →B →C

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46
Q

What is mixed replication?

A

leveraging a combination of both cascade and fan-out or fan-out and cascade

A →B and B →C and B →D

47
Q

What are proxy NAS servers in Unity XT?

A

ability to access all the file system/snapshot data on the destination NAS server through SMB and NFS

read only even if snapshot accessed is read/write =

48
Q

When can proxy NAS servers be used on Unity XT?

A

works for both synchronous and asynchronous replication

for synchronous replication the destination file system isn’t fully mounted and not accessible

49
Q

What are read/write SMB proxy shares on Unity XT?

A

ability to create SMB shares for writable and read only snapshots on the destination NAS server

designed to enable DR testing without any impact to ongoing replication session

works with both synchronous and asynchronous replication

50
Q

What is file level retention (FLR) on Unity XT?

A

enables the ability to lock files - prevents them from being modified or deleted until a specific retention date

51
Q

What systems does Unity XT support native file import?

A

VNX1 and VNX2

52
Q

What is EMCopy?

A

command line tool developed by Dell for file data migration

53
Q

What is Robocopy?

A

tool for performing Windows host based file replication

54
Q

What is Rsync?

A

used to transfer file data for Linux users

55
Q

What is PowerPath Migration Enabler?

A

migration tool for block data from legacy Dell systems

56
Q

What Unity system doesn’t support data reduction?

A

UnityVSA (since data reduction requires write caching capabilities)

57
Q

What is the required flash in a pool to enable data reduction?

A

more than 10%

58
Q

What is the relationship between replication and data reduction on Unity XT?

A

asynchronous and synchronous operations support data reduction

both source and destination system can have it enabled/disabled

59
Q

How does data reduction work on Unity XT?

A

data saved and written to system cache - write acknowledged w/ host

cache sends data to DR algorithm during flush and algorithm determines if savings are possible

space allocated on storage resource for data set - data saved to disk

60
Q

What happens before data is sent to the data reduction algorithm in Unity XT?

A

first segmented into 8KB blocks

61
Q

What happens in a read operation with data that has been reduced?

A

data must be recreated within System Cache in its original form so it can be sent to host

62
Q

When can you enable data reduction on a storage resource in Unity?

A

at any time

63
Q

What is Local LUN Move (aka Move)?

A

used to move data from a supported source Block resource to a target block resource within the same system

can be within the pool or between pools - between one data reduction pool and another non-data reduction pool

64
Q

What is the relationship between data reduction and D@RE?

A

not impacted by D@RE as all data reduction operations occur on data residing in system cache before hitting backend disks

data decrypted before being sent to system cache in read operations

65
Q

What is a thin clone?

A

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

66
Q

What are the drive partnership group rules?

A

same type drives but can be different sizes (SSD Flash 3 600GB can go with SSD Flash 3 1.6TB)

in spinning disk - different RPMs get put in different partnership groups (10Ks separated from 15Ks even if same size)

different flash types are in separate drive partnership groups

67
Q

what is the max number of drives in a drive partnership group?

A

64

68
Q

what is the mininimum number of drives in a drive partnership group based on?

A

RAID type + stripe width

69
Q

What happens when a drive partnership group is full?

A

another minimum number of drives is needed to create the next drive partnership group with the same RAID type and stripe width

70
Q

What are drive extents and what determines there size?

A

portion of a drive GBs in size - either for user data or spare space

determined by drive type (EX: all SSD Flash 3 drives have same size extents but 400GB drive has less extents of that size than 800GB size)

71
Q

What is the order of creation in Unity Dynamic Pools?

A

drive partnership group

drive extent

RAID extent

private RAID group

private LUN

72
Q

What is the minimum number of drives in a RAID 5 dynamic pool?

A

6 (4+1) + 1 hot spare

73
Q

What is the minimum number of drives in a RAID 6 dynamic pool?

A

7 (4+2) + 1 hot spare

74
Q

What is the minimum number of drives in a RAID 1/0 dynamic pool?

A

3 (1+1) + 1 hot spare

75
Q

What is the spare drive rule in Unity XT?

A

1 per 32 OF A GIVEN TYPE

EX:

9x 600GB SAS 15K

9x 1200GB SAS 10K

9x 1800GB SAS 10K

3 total spares:

1x 600GB SAS 15K

1x 1200GB SAS 10K

1x 1800GB SAS 10K

27x 1200GB SAS 10K

1 total spare:

1x 1200GB SAS 10K

76
Q

For what Unity XT features are thin storage objects recommended?

A

data reduction

snapshots

thin clones

asynchronous replication

77
Q

What is SAN Copy?

A

provides one time migration of block resources from a third party array over iSCSI or FC

78
Q

What is the relationship between RAID and pool tiers?

A

single RAID protection chosen for each tier

once RAID protection is selected and pool created the RAID protection can’t be changed

79
Q

What are the performance metrics of the extreme performance tier in Unity XT?

A

user response = less than 1 - 5 milliseconds

multi-access response = less than 10 milliseconds

80
Q

What are the performance metrics of the performance tier in Unity XT?

A

user response = 5 milliseconds

multi-access response = 10 - 50 milliseconds

81
Q

What are the performance metrics of the capacity tier in Unity XT?

A

user response = 7-10 milliseconds

multi-access response = less than 100 milliseconds

82
Q

How do capacity (NL-SAS) drives handle large block IO?

A

leverages system cache for sequential and large block IO

more efficient servicing

83
Q

What are the strengths of the extreme performance (flash) drives in FAST VP?

A

extremely fast access for reads

handles multiple sequential workloads better than SAS or NL-SAS

84
Q

What are the strengths of the SAS/NL-SAS drives in FAST VP?

A

sequential reads leverage prefetching of data

sequential writes leverage system optimizations favoring drive

85
Q

What should you keep in mind with flash drives in FAST VP?

A

writes perform slower than reads

heavy concurrent writes affect read performance

single threaded large sequential IO performance equivalent to SAS

86
Q

What should you keep in mind with NL-SAS drives in FAST VP?

A

long response times typically seen for heavy write workloads

87
Q

How is data sliced up in FAST VP?

A

256MB slices

88
Q

How is data sliced up in FAST CACHE?

A

64KB blocks

89
Q

Where is the memory map located in Unity XT?

A

resides in DRAM memory and on system drives to maintain high availability

90
Q

What is a FAST Cache promotion?

A

operation of copying data from spinning media to a location within FAST Cache

91
Q

How is a read performed with FAST Cache?

A

IO request sent down

scans to see if its in system cache

not there - looks at memory map to see if its in FAST Cache

if not goes to down to drives - drives copy data to system cache for host to receive

92
Q

How is a write performed with FAST Cache?

A

system cache receives write

held temporarily to see if memory map can locate a copy of the new write on FAST Cache

if it is it’s written directly to FAST Cache if not its sent to the drives and acknowledge by cache and host

93
Q

What is page cleaning in FAST Cache?

A

occurs when FAST Cache needs to synchronize the contents of a page with the data’s location in the pool

done to reduce the number of dirty pages to give spare space

94
Q

What are the drive sizes and number of drives needed for each Unity model for FAST CACHE?

A

Unity XT 380 400 GB 800 GB (4 Drives)

Unity XT 480 400 GB 1.2 TB (6 Drives)

Unity XT 680 400 GB 3.2 TB (16 Drives)

Unity XT 880 400 GB 6 TB (30 Drives)

95
Q

What is the operational difference between FAST Cache and FAST VP?

A

frequently accessed data on spinning drive is COPIED to FAST Cache

data is PHYSICALLY MOVED between pool tiers in FAST VP

96
Q

What is the timing difference between FAST Cache and FAST VP?

A

FAST Cache is always active

FAST VP relocation occurs during user specified relocation window

97
Q

Where is system cache positioned vs FAST Cache?

A

system cache = closest to CPU / lowest latency

FAST cache = between system cache and pool drives

98
Q

What is system cache best suited for?

A

sequential IO
IO larger than 64KB
zero fill requests
high-frequency access patterns

99
Q

What is FAST Cache best suited for?

A

random IO
IO smaller than 64KB
data with a high locality

100
Q

What is the size difference between system cache and FAST cache?

A

fixed 8KB page size (system cache)

fixed 64KB page size (FAST cache)

101
Q

What is the availability difference between FAST Cache and system cache?

A

contents of system cache are volatile - BBU powers system in failure until all dirty pages copied to the mSATA drive

contents of FAST Cache are non-volatile and can withstand power loss

102
Q

What is Redirect on Write snapshots in Unity XT?

A

after snapshot is taken new writes to snapped storage resource to the primary storage are redirected and written to a new location within the storage pool

103
Q

What is benefit of Redirect on Write snapshots in Unity XT?

A

no need to define separate protection space or to copy data to a separate location before writing to snapped blocks

new data is simply written to a new location in the same pool

104
Q

What is a consistency group?

A

allows admins to provision multiple LUNs within a crash consistent group which allow LUNs to be uniformly protected at same PIT

105
Q

What is necessary for site to site replication between Unitys?

A

the source and destination storage resource must be of the same type:

LUNs
Consistency groups
VMware VMFS datastores
Thin clones
File systems and VMware NFS datastores

106
Q

What are the replication options for synchronous replication on Unity?

A

one-directional
bi-directional

107
Q

What is the relationship between VLANs and asynchronous replication?

A

can do replication interfaces on different VLANs for multi-appliance replication

108
Q

What are the asynchronous replication types that are supported by Unity XT?

A

one-directional

bi-directional

one-to-many

many-to-one

109
Q

What is bridged file replication in Unity XT?

A

A single file resource simultaneously replicating synchronously and asynchronously to two systems, while the destination system for the synchronous replication is also asynchronously replicating to a third system

110
Q

What is the limitation of mixed file replication?

A

combination can be configured if each resource doesn’t exceed four total replication sessions

111
Q

What is a limitation for any advanced file replication topology?

A

can’t configure a replication session to a resource that is already a replication destination for another resource

112
Q

At what level is advanced replication topologies managed?

A

NAS Server level

113
Q

What are the memory configurations for each model?

A

380 = 128GB
480 = 192GB
680 = 384GB
880 = 768GB

114
Q

What are the FAST Cache configurations for each model?

A

380 = 800GB
480 = 1.2TB
680 = 3.2TB
880 = 6TB

Dell Midrange Storage Solutions Design 2023 (18 decks)

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