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Dell PowerFlex Solutions Design 2023 > Dell EMC PowerFlex: Networking Best Practices and Design Considerations > Flashcards

Dell EMC PowerFlex: Networking Best Practices and Design Considerations Flashcards

1
Q

How many SDSs can a PowerFlex system support?

A

512

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2
Q

What are the max number of SDCs in a PowerFlex system?

A

1024

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3
Q

What happens when a component fails in PowerFlex?

A

MDM initiates a auto-healing process

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4
Q

What is the recommended networking configuration for front and backend PowerFlex networking paths?

A

recommended to separate back-end traffic since it allows for improved rebuild/rebalance

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5
Q

What is SDC to SDC traffic?

A

front-end

includes all writes/reads arriving at or originating from a client

has a high throughput requirement

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6
Q

What is SDS to SDS traffic?

A

back-end

includes writes mirrored between SDSs, rebalance traffic, rebuild traffic, volume migration

high throughput requirement

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7
Q

What is MDM to MDM traffic?

A

back-end traffic

relatively lightweight data exchange

do not require same level of throughput required for SDC/SDS traffic

have very short timeout for their quorum exchanges (happens every 100ms)

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8
Q

What is the network requirement for MDM to MDM traffic?

A

stable, reliable low latency network

PowerFlex supports the use of one or more networks dedicated to MDM traffic

min 2 10G uplinks per MDM for prod environments - 25G recommended

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9
Q

What is the latency requirement for peer MDM to MDM traffic in a replication use case?

A

less than 200ms

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10
Q

What are MDMs responsible for besides mapping?

A

rebalance/rebuild traffic, RCGs, metadata synchronization for replication purposes

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11
Q

What is MDM to SDC traffic?

A

front-end

primary MDM must communicate with SDCs in event that data layout changes

can happen if node goes offline/volumes put into RCG

connection is lazy/asynchronous but still requires reliable low latency network

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12
Q

What is MDM to SDS traffic?

A

back-end

primary MDM must communicate w/ SDSs to monitor device health/issue rebalance/rebuilds

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13
Q

What is SDC to SDR traffic?

A

front-end traffic

in volume replication normally SDC to SDS traffic is routed through SDR

if volume is in RCG MDM adjusts the volume mapping presented to the SDC and directs SDC to issue IO operations to SDRs to pass onto relevant SDSs

high throughput requirement

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14
Q

What is SDR to SDS traffic?

A

back-end traffic - throughput is proportionate to number of volumes being replicated

when volumes are being replicated there are two subsequent IOs from the SDR to the SDSs on source system

SDR passes volume IO to associated SDS for processing/committal to disk

SDR applies writes to journaling volume

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15
Q

How does PowerFlex recognize journal volumes?

A

sees them as a normal volume

SDR sends IO to the SDSs whose disks comprise the SP in which the journal volume resides

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16
Q

What is MDM to SDR traffic?

A

MDMs must communicate w/ SDRs to issue journal interval closures, collect/report RPO compliance and maintain consistency

commands local SDRs to perform journal operations

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17
Q

What is SDR to SDR traffic?

A

SDRs within source or within target don’t communicate w/ one another

SDRs across systems communicate w/ one another

latency not sensitive but round trip time should be less than 200ms

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18
Q

How do SDCs communicate with one another?

A

SDCs do not communicate w/ one another

can be enforced using private VLANs and network firewalls

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19
Q

What is the fault tolerance rule for PowerFlex software components?

A

communicated between software components should be assigned to at least two subnets on different physical networks

native link fault tolerance and multipathing on all of these components across subnets assigned

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20
Q

What happens if a link failure is detected by PowerFlex?

A

almost immediate awareness of issue

dynamically adjusts communications within 2-3 seconds across subnets assigned to software components where link failure was

particularly important for SDS - SDS and SDC - SDS communication

21
Q

What networking topology is strongly recommended to not be used for PowerFlex?

A

STP (spanning tree protocol)

Dell recommends using a non-blocking network design (use of all switch ports concurrently)

22
Q

What is a two-tier spine leaf topology?

A

provides single switch hop between leaf switches and large amount of bandwidth between endpoints

eliminates oversubscription of uplink ports

23
Q

How is a spine-leaf topology connected?

A

each leaf switch is connected to all spine switches

leaf switches don’t need to be directly connected to each other

spine switches don’t need to be connected to other spine switches

24
Q

Why does Dell recommend a spine-leaf topology in most instances?

A

scalability to hundreds of nodes

facilitate scale out deployments without needing to rearchitect the solution

allows use of all network links concurrently

25
Q

When would Dell recommend a flat network topology over a spine leaf?

A

if existing flat network is being extended or if network is not expected to scale

26
Q

How is a flat network topology connected?

A

all the switches are used to connect to hosts - no spine switches

27
Q

When might a flat network topology be cost prohibitive compared to a spine-leaf?

A

if you expand beyond small # of access switches

additional cross-link ports required could run up costs quickly

28
Q

What are latency best practices for PowerFlex sizing?

A

latency for all SDS-SDC communication should never exceed 1ms network-only round trip time under normal operations

since most WANs lowest response time is more than this you should not operate PowerFlex clusters across a WAN

29
Q

What are latency best practices for PowerFlex replication sizing?

A

latency between peered cluster components whether MDM-MDM or SDR-SDR should not exceed 200ms round trip time

30
Q

Outside of performance what is the important of right sizing network throughput for PowerFlex?

A

reduce rebalance/rebuild times

31
Q

What is the minimum link network for throughput on PowerFlex?

A

10G - 25G recommended

32
Q

What do all PowerFlex nodes ship with?

A

4 ports at 25G minimum

33
Q

What is the relation between SDS and throughput?

A

SDSs that make up a PD should reside on hardware w equivalent storage/network performance

since total bandwidth of PD will be limited by the weakest link during IO and rebuild/rebalance operations due to wide striping

34
Q

Why do node types need to be the same in a PD when it comes to throughput?

A

HCI nodes have slower performance than bare metal nodes due to virtualization overhead

35
Q

What is the networking redundancy recommendation for PowerFlex nodes?

A

each node has at least 2 separate network connections regardless of throughput requirement

36
Q

What is the rule of network throughput for the appliance as a whole?

A

throughput to a node should match or exceed the combined maximum throughput of the storage media hosted on the node

37
Q

How would you calculate the amount of throughput required on a node?

A

When determining the amount of network throughput required, keep in mind that modern media performance
is typically measured in megabytes per second, but modern network links are typically measured in gigabits
per second.
To translate megabytes per second to gigabits per second, first multiply megabytes by 8 to translate to
megabits, and then divide megabits by 1,000 to find gigabits.

38
Q

What is the typical measure for bandwidth requirement on a node?

A

read operations

39
Q

What is important to consider about the networking components for throughput requirements on a node?

A

verify RAID controller/HBA on node can meet or exceed maximum throughput of underlying storage media

40
Q

What is important to know about bandwidth in write heavy environments/nodes?

A

per SDS a write operation requires 1.5 times more bandwidth/throughput than a read operation when compared to the throughput of the underlying storage

41
Q

For HCI nodes what is the priority for network sizing?

A

VM Performance

must separate storage from other network traffic

42
Q

What is IP redundancy connectivity on an HCI node?

A

recommended for MDMs

good for SDSs

good for SDCs if 3sec interrupt on failure is acceptable

43
Q

What is MLAG connectivity on an HCI node?

A

good for SDCs when minimum IO interrupt on failure needed

ok for SDSs

not recommended for MDMs

44
Q

When might it be beneficial to isolate front end and backend traffic for the storage network?

A

in two layer deployments where storage and virtualization/compute teams each manage their own networks

guarantee performance on storage/compute

45
Q

Why are jumbo frames recommended?

A

allows more data to be passed in a single Ethernet frame

decreases total number of frames and number of interrupts to be processed by a node

performance benefit of around 10%

46
Q

What is the difference between IP redundancy and MLAG/LAG connectivity?

A

LAG - combines ports between end points

IP - each physical port has its own IP address

47
Q

Why is LAG/IP redundancy recommended over MLAG for MDM-MDM traffic?

A

continued availability of one IP address on the MDM helps prevent failovers due to short timeouts between MDMs

48
Q

Why is IP level redundancy preferred over MLAG for SDC communication links?

A

improved network failure resistence in v3.5

49
Q

What is the difference between MLAG (multi-chassis link aggregation groups) and LAG?

A

like LAG MLAG provides network link redundancy

unlike LAG MLAGs allow a single node to be connected to multiple switches

Dell PowerFlex Solutions Design 2023 (11 decks)

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