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
2
Q
What is FAST VP?
A
fully automated storage tiering for virtual pools
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
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
5
Q
What is the Highest Available Tier policy in FAST VP?
A
when quick responses are a priority
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
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
8
Q
What is the Lowest Available Tier policy in FAST VP?
A
when cost effectiveness is highest priority
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
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
11
Q
How does FAST VP help with Unity XT performance?
A
automatically moves data within a pool to appropriate drive technology
12
Q
When is FAST VP most effective for Unity XT?
A
if data relocation occurs during or immediately after normal daily processing
13
Q
How should you configure FAST VP for highly active applications?
A
for relocation to run constantly
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
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
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
17
Q
What process does FAST Cache do during reads?
A
driver copies data off the disk being accessed in FAST Cache
18
Q
What process does FAST Cache do during writes?
A
effectively buffers the data waiting to be written to disk
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
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
21
Q
What happens when data sitting in FAST Cache gets less frequently accessed?
A
data is flushed out of cache
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
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
24
Q
How are the FAST Cache policies defined?
A
system defined and can’t be modified by the user
25
What is the FAST Cache memory map?
contains information about all the 64KB blocks currently residing in FAST Cache
each time promotion/demotion occurs map is updated
26
Where is the FAST Cache memory map located in Unity XT?
resides in DRAM memory and system drives
27
How does the FAST Cache memory map work?
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
28
What is a FAST Cache flush?
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
29
What is FAST Cache cleaning?
proactively copies dirty pages to underlying physical drives during times of minimal backend activity
30
What is each RAID 1 pair in FAST Cache called?
FAST Cache object
31
How do you expand FAST Cache?
in pairs - can do it up to the system maximum
32
What is a FAST Cache shrink operation?
allows the removal of all but 2 drives from FAST Cache
33
What is the performance benefit of FAST Cache on Unity HFA?
can increase the achieveable IOPS of the system
34
What is a result of higher IOPS potential from FAST Cache on Unity HFA?
system has higher CPU utilization since additional IO must be serviced
why you should monitor current utilization before enabling
35
What should an admin do before configuring FAST Cache?
add a flash tier to the hybrid pool
36
What workloads would call for FAST Cache utilization in a Unity HFA?
if workload is highly transactional and has a high degree of locality that changes rapidly
37
When is it more beneficial to increase the flash tier in a Unity HFA than use FAST Cache?
apps that use larger IO sizes - have low skew - or do not change locality quickly
38
What type of data reduction does Unity XT have?
Inline
39
Where does data reduction take place in Unity XT?
in buffer cache before destaging to disk
40
What is the logical algorithm on Unity XT data reduction?
zero detection and deduplication
41
When do processor cycles occur on Unity XT?
only used for deduplication and compression logic
42
What is required for data reduction to be enabled on Unity XT?
pool must contain a flash tier
total usable capacity of flash tier must meet or exceed 10% of the pool
43
Where is data reduction supported on Unity XT systems?
supported on all thin provisioned resources that are created from All Flash and Hybrid flash pools
affects all incoming writes once enabled
44
What is advanced deduplication on Unity XT?
dynamic deduplication algorithm which reduces storage consumption by eliminating duplicate 8KB blocks within a storage resource
45
How does advanced deduplication work on Unity?
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
46
What Unity system doesn't support data reduction?
UnityVSA
47
What is deduplication?
use algorithms to perform pattern detection and store only a single instance of data
48
What is compression?
encodes data using fewer bits than the original representation
49
What is zero detection?
logically detects and discards consecutive zeros - saves only one instance - uses pointers
50
What is the performance impact of data reduction on Unity XT?
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
51
What are the 3 parts of Powerstore data reduction?
compression
deduplication
zero detection
52
At what level does deduplication work in Powerstore?
at the block level at 4KB granularity
53
What happens to Powerstore data reduction during high write activity?
may defer the deduplication of data and devote resources to servicing the client workloads
54
What happens to Powerstore during low activity periods?
will use excess resources to re-examine any data written during high write periods for duplicates to regain space savings
55
What are snapshots?
point in time copies of block and file resources
56
What are the supported source of snapshots on Unity XT?
LUNs
consistency group LUNs
file systems
VMWare VMFS data stores
NFS data stores
57
How are snapshots created on Unity?
manually or through a schedule
58
What is the benefit of using Unity snapshots?
restoration is instant and does not use extra storage space
59
How are snapshots supported in Unity XT?
supported on both physical Unity and UnityVSA
60
What are hierarchical snapshots in Unity XT?
snapshots of snapshots
can go 10 levels deep
61
What are snapshots the foundation of in Unity XT?
asynchronous replication
62
What is the relationship between LUNs and snapshots in Unity XT?
consistency group snapshots apply to all LUNs in the group
restoring a consistency group snapshot means all members are restored
63
What are the performance recommendations when enabling snapshots in Unity XT?
include a flash tier in a hybrid pool where snapshots are active
64
What performance impact do snapshots have on Unity XT?
increase overall CPU load
increase overall drive IOPS
65
What capacity impact do snapshots have on Unity XT?
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
What are the operation recommendations for snapshots on Unity XT?
schedule snapshots operations after any FAST VP relocation has completed
staggering snapshots operations on different schedules (creation, deletion, etc.)
67
What is a thin clone?
read/write copy of a thin block storage resource that shares blocks with the parent resource
68
How do thin clones utilize snapshots in Unity XT?
use snapshots to provide space efficient clones for block objects
69
What is a Base LUN family in Unity XT?
combination of Base LUN and all its derivative thin clones/snapshots
70
What is a Base LUN in Unity XT?
original or production LUN for a set of derivative snapshots and thin clones
71
What platforms are thin clones supported on Unity XT?
both physical and UnityVSA
72
How are thin clones created on Unity XT?
from attached read only or unattached snapshots with no auto-deletion policy and no expiration policy set
73
How do thin clones effect performance on Unity XT?
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
What is the performance recommendation for Unity XT when implementing thin clones?
including flash tier in a hybrid pool where thin clones are active
75
What is data availability with thin clones on Unity XT?
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
What are the supported storage resources for snapshots on Powerstore?
volume
volume group
virtual machines
file system
77
What are the supported storage resources for thin clones on Powerstore?
NAS Server
file system
file system snapshot
volume
volume group
78
What is important to know about volume snapshots on Powerstore?
volume snapshots are read only
cannot add to - delete from - change contents of volume snapshots
79
What is important to know about file system snapshots on Powerstore?
can be refreshed
80
How do you access a snapshot on Powerstore?
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
What is the performance impact of thin clones and snapshots on Powerstore?
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
What is asynchronous replication mostly used for?
replicate data over long distances
83
What performance impact does asynchronous replication have on Unity XT?
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
How do remote and local systems communicate in asynchronous replication on Unity XT?
formed from replication interfaces
IP based connections established on each system
85
How is the replication session managed in asynchronous replication?
communication channel required
management channel established on a Replication Connection
channel defines management interfaces and credentials for each system
86
What are the minimum and maximum configurable RPO on Unity XT asynchronous replication?
5 minutes - 1440 minutes (24 hours)
87
How is local replication performed on Unity XT?
asynchronously within the same storage system
storage resources are replicated from one storage pool to another
88
How does local replication on Unity XT incorporate snapshots?
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
What storage resources are supported for local replication?
LUNs/Consistency Groups
thin clones
VMWare VMFS/NFS data stores
NAS Servers/file systems
90
What are the performance recommendations for Unity XT asynchronous replication?
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
How should you configure RPO on replication sessions in Unity XT?
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
Why should you fill a storage object with data before creating a replication session from it on Unity XT?
fastest way to populate the destination storage
93
What is synchronous replication?
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
What is the performance effect of synchronous replication?
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
What is the advantage of synchronous replication?
ensures zero RPO between the local and replica
96
How is synchronous replication run on Unity XT?
uses write intent logs (WIL) on each of the systems
97
What do WILs do in synchronous replication on Unity XT?
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
What is the distance limitation on synchronous replication in Unity XT?
generally 60 mi (100km) between sites
99
What is the recommended latency between systems in synchronous replication with Unity XT?
less than 10 milliseconds
100
How is a synchronous replication connection established on Unity XT?
data connection through FC
communication channel required to manage replication sessions
part of management provided using Replication Interfaces
101
What is the perfomance recommendation when performing synchronous replication on Unity XT?
include a Flash tier in a hybrid pool - applies to both source and destination pools
102
How is data transferred in synchronous replication in a Unity XT?
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
Why should you create the synchronous replication session first before filling the source storage in Unity XT?
filling source object alleviates need to perform initial synchronization of the replication session
fastest way to populate destination session object w/ synchronous replication
104
On what Unity systems are replication sessions available?
only on physical systems
105
What does Unity XT file remote protection support?
combination of synchronous and asynchronous remote replication sessions together
106
What is the encryption method in Unity XT?
controller based D@RE
uses hardware that is embedded in all SAS IO modules and SPs
107
What performance impact does D@RE have on Unity XT?
encryption and decryption occur with minimal impact on data services like replication/deduplication
108
What is the advantage of D@RE over SEDs?
simple, lower cost, and more maintainable
drive vendor/type agnostic - eliminates drive specific vendor overhead
109
How does D@RE protect data?
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
What is external key management on D@RE?
data is protected from access if the storage system is stolen or while a planned relocation to a different site is happening
111
What are the encryption recommendations for Unity XT?
recommends ordering with encryption enabled - can only be enabled at time of system installation with appropriate license
112
What happens when encryption is enabled in Unity XT?
internal key manager generates and manages encryption keys
recommend making external backup of these keys
113
How do you decommission a Unity XT?
deleting pools
deletes all drive encryption keys and eliminates the necessity to shred disk drives
114
What does Powerstore D@RE protect from?
stolen drives
during transit
discarded drives
115
What are the components required for Powerstore encryption?
SEDs
Key Management Service (KMS)
116
What is required to keep encryption on Powerstore after adding or removing a drive?
keystore file must be backed up
if KMS fails or keystore file cannot be read encrypted data can't be accessed
117
When is Powerstore encryption enabled?
automatically activated during the initial configuration of the system
118
What is important about scalability with Powerstore encryption?
adding non-SED drives to an appliance is not supported
adding an unencrypted appliance to an encrypted cluster is not supported
119
What is the internal key management for Powerstore encryption?
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
What is the Host IO Limits feature on Unity XT?
limits initiator IO operations to the block storage resources
can be set on physical or virtual deployments of Unity
121
When are Host IO limits active in Unity XT?
when policies are created and assigned to the storage resources - provides system wide pause and resume controls
122
What are the Host IO limit policies in Unity XT?
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
What are the limits on the Host IO Limit feature?
only one IO limit policy can be applied to an individual LUN or a LUN that is a member of a consistency group
124
What if both the throughput and bandwidth limits are in place for Host IO Limits in Unity?
system limits the traffic according to the threshold that is reached first
125
What are the performance recommendations for implementing Host IO Limits in Unity XT?
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
Why may it be beneficial to implement Host IO Limits on snapshots in Unity?
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
What is the configuration recommendation for provisioning file storage on an ESXi host on Unity XT?
create VMWare NFS Datastores instead of general purpose NFS file systems
optimized to provide better performance with ESXi
128
How show VMWare NFS Datastores be configured on Unity XT?
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
How show vVol (File) Datastores be configured on Unity XT?
create at least two vVol-enabled NAS Servers for each SP
130
What are the configuration recommendations to optimize performance for Powerstore X?
create additional internal iSCSI targets
increase internal iSCSI queue depths
enable jumbo frames
131
What do Dell Unity systems require to deliver the maximum IOPS?
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
When should you use thick storage objects on Unity XT?
for workloads that require high bandwidth for sequential streaming data
133
Why woudl thick storage objects be recommended for sequential streaming workloads?
thick objects fully allocate capacity before application use and in a consistent manner - can improve subsequent sequential access
134
What features are thick objects not compatible with on Unity XT?
data reduction
snapshots
asynchronous replication
