Midrange Storage Performance Planning: Data Services and Array Features Flashcards
What models is FAST VP supported on Unity XT?
Unity HFA
UnityVSA
What is FAST VP?
fully automated storage tiering for virtual pools
What is the advantage of using mixed pools in Unity HFA?
reducing cost of configuration by reducing drive counts and using large capacity drives
What are tiering policies in FAST VP?
determine how the data relocation takes place within a storage pool
access patterns for all data within a pool are compared against each other
What is the Highest Available Tier policy in FAST VP?
when quick responses are a priority
What is the Auto Tier policy in FAST VP?
automatically relocates data to the most appropriate tier based on the activity level of each slice
What is the Start High, Then Auto Tier policy in FAST VP?
recommended policy for each newly created pool
takes advantage of Highest Available and Auto tier policies
What is the Lowest Available Tier policy in FAST VP?
when cost effectiveness is highest priority
What is the default policy in FAST VP?
Start High Then Auto Tier
places initial allocation of objects in highest tier available - monitors activity of the object to determine correct placement
How does the tiering process in FAST VP work?
tracks data in a storage pool per slice (256MB)
ranks slices according to level of activity - automated
most utilized data is on hot tier
How does FAST VP help with Unity XT performance?
automatically moves data within a pool to appropriate drive technology
When is FAST VP most effective for Unity XT?
if data relocation occurs during or immediately after normal daily processing
How should you configure FAST VP for highly active applications?
for relocation to run constantly
What is the appropriate free capacity for FAST VP to work correctly?
recommended at least 10% free capacity in storage pools so relocation can occur efficiently
What’s the main benefit of FAST Cache?
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
What does FAST Cache consist of?
one or more RAID 1 pairs of SAS flash 2 drives
provides both read/write caching
What process does FAST Cache do during reads?
driver copies data off the disk being accessed in FAST Cache
What process does FAST Cache do during writes?
effectively buffers the data waiting to be written to disk
How does FAST Cache work?
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
What is the performance benefit of FAST Cache?
reduces the load on the underlying disks of the LUNs that will ultimately contain data
What happens when data sitting in FAST Cache gets less frequently accessed?
data is flushed out of cache
What is the FAST Cache policy engine?
software that monitors and manages the IO flow through FAST Cache
keeps statistics to determine what data is good for promotion
When does data become eligible for promotion to FAST Cache?
when an eligible block is accessed from spinning drives three times within a short period of time
How are the FAST Cache policies defined?
system defined and can’t be modified by the user
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
Where is the FAST Cache memory map located in Unity XT?
resides in DRAM memory and system drives
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
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
What is FAST Cache cleaning?
proactively copies dirty pages to underlying physical drives during times of minimal backend activity
What is each RAID 1 pair in FAST Cache called?
FAST Cache object
How do you expand FAST Cache?
in pairs - can do it up to the system maximum
What is a FAST Cache shrink operation?
allows the removal of all but 2 drives from FAST Cache
What is the performance benefit of FAST Cache on Unity HFA?
can increase the achieveable IOPS of the system
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
What should an admin do before configuring FAST Cache?
add a flash tier to the hybrid pool
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
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
What type of data reduction does Unity XT have?
Inline
Where does data reduction take place in Unity XT?
in buffer cache before destaging to disk
What is the logical algorithm on Unity XT data reduction?
zero detection and deduplication
When do processor cycles occur on Unity XT?
only used for deduplication and compression logic
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
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
What is advanced deduplication on Unity XT?
dynamic deduplication algorithm which reduces storage consumption by eliminating duplicate 8KB blocks within a storage resource
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
What Unity system doesn’t support data reduction?
UnityVSA
What is deduplication?
use algorithms to perform pattern detection and store only a single instance of data
What is compression?
encodes data using fewer bits than the original representation
What is zero detection?
logically detects and discards consecutive zeros - saves only one instance - uses pointers
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
What are the 3 parts of Powerstore data reduction?
compression
deduplication
zero detection
At what level does deduplication work in Powerstore?
at the block level at 4KB granularity
What happens to Powerstore data reduction during high write activity?
may defer the deduplication of data and devote resources to servicing the client workloads
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
What are snapshots?
point in time copies of block and file resources
What are the supported source of snapshots on Unity XT?
LUNs
consistency group LUNs
file systems
VMWare VMFS data stores
NFS data stores
How are snapshots created on Unity?
manually or through a schedule
What is the benefit of using Unity snapshots?
restoration is instant and does not use extra storage space
How are snapshots supported in Unity XT?
supported on both physical Unity and UnityVSA
What are hierarchical snapshots in Unity XT?
snapshots of snapshots
can go 10 levels deep
What are snapshots the foundation of in Unity XT?
asynchronous replication
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
What are the performance recommendations when enabling snapshots in Unity XT?
include a flash tier in a hybrid pool where snapshots are active
What performance impact do snapshots have on Unity XT?
increase overall CPU load
increase overall drive IOPS
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
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.)
What is a thin clone?
read/write copy of a thin block storage resource that shares blocks with the parent resource
How do thin clones utilize snapshots in Unity XT?
use snapshots to provide space efficient clones for block objects
What is a Base LUN family in Unity XT?
combination of Base LUN and all its derivative thin clones/snapshots
What is a Base LUN in Unity XT?
original or production LUN for a set of derivative snapshots and thin clones
What platforms are thin clones supported on Unity XT?
both physical and UnityVSA
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
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
What is the performance recommendation for Unity XT when implementing thin clones?
including flash tier in a hybrid pool where thin clones are active
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
What are the supported storage resources for snapshots on Powerstore?
volume
volume group
virtual machines
file system
What are the supported storage resources for thin clones on Powerstore?
NAS Server
file system
file system snapshot
volume
volume group
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
What is important to know about file system snapshots on Powerstore?
can be refreshed
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
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
What is asynchronous replication mostly used for?
replicate data over long distances
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
How do remote and local systems communicate in asynchronous replication on Unity XT?
formed from replication interfaces
IP based connections established on each system
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
What are the minimum and maximum configurable RPO on Unity XT asynchronous replication?
5 minutes - 1440 minutes (24 hours)
How is local replication performed on Unity XT?
asynchronously within the same storage system
storage resources are replicated from one storage pool to another
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
What storage resources are supported for local replication?
LUNs/Consistency Groups
thin clones
VMWare VMFS/NFS data stores
NAS Servers/file systems
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
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
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
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
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
What is the advantage of synchronous replication?
ensures zero RPO between the local and replica
How is synchronous replication run on Unity XT?
uses write intent logs (WIL) on each of the systems
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
What is the distance limitation on synchronous replication in Unity XT?
generally 60 mi (100km) between sites
What is the recommended latency between systems in synchronous replication with Unity XT?
less than 10 milliseconds
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
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
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
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
On what Unity systems are replication sessions available?
only on physical systems
What does Unity XT file remote protection support?
combination of synchronous and asynchronous remote replication sessions together
What is the encryption method in Unity XT?
controller based D@RE
uses hardware that is embedded in all SAS IO modules and SPs
What performance impact does D@RE have on Unity XT?
encryption and decryption occur with minimal impact on data services like replication/deduplication
What is the advantage of D@RE over SEDs?
simple, lower cost, and more maintainable
drive vendor/type agnostic - eliminates drive specific vendor overhead
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
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
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
What happens when encryption is enabled in Unity XT?
internal key manager generates and manages encryption keys
recommend making external backup of these keys
How do you decommission a Unity XT?
deleting pools
deletes all drive encryption keys and eliminates the necessity to shred disk drives
What does Powerstore D@RE protect from?
stolen drives
during transit
discarded drives
What are the components required for Powerstore encryption?
SEDs
Key Management Service (KMS)
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
When is Powerstore encryption enabled?
automatically activated during the initial configuration of the system
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
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
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
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
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
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
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
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
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
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
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
How show vVol (File) Datastores be configured on Unity XT?
create at least two vVol-enabled NAS Servers for each SP
What are the configuration recommendations to optimize performance for Powerstore X?
create additional internal iSCSI targets
increase internal iSCSI queue depths
enable jumbo frames
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
When should you use thick storage objects on Unity XT?
for workloads that require high bandwidth for sequential streaming data
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
What features are thick objects not compatible with on Unity XT?
data reduction
snapshots
asynchronous replication
