doc.: ieee 802.11-09/1222r1 submission november 2009 eldad perahia, intel corporationslide 1 hard...
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November 2009
Eldad Perahia, Intel Corporation
Slide 1
doc.: IEEE 802.11-09/1222r1
Submission
Hard Disk Drive Traffic Model for TGadDate: 2009-11-17
Name Company Address Phone email Eldad Perahia Intel
Corporation
2111 NE 25th Ave Hillsboro, OR 97124
503-712-8081 [email protected]
Robert Stacey Intel Corporation
Mark Grodzinsky Wilocity [email protected]
Authors:
November 2009
Eldad Perahia, Intel Corporation
Slide 2
doc.: IEEE 802.11-09/1222r1
Submission
Background
• TGad Evaluation Methodology document includes a “hard disk file transfer” application– Enterprise cubicle scenario
– File transfer wirelessly between laptop and hard drive
• Traffic model is TBD
November 2009
Eldad Perahia, Intel Corporation
Slide 3
doc.: IEEE 802.11-09/1222r1
Submission
Measured Data and Modeling
• Hard Disk test in the PCMark Vantage benchmarking suite used to capture sample trace
• Specific subtest captured was “Importing pictures to Windows Photo Gallery”
– Reading a large collection of picture files from the hard drive
• Data captured is the transactions size and request time of the transactions
– Transactions are all reads from the hard drive– Requests can be overlapping in time, i.e. a subsequent request arrives before
the previous transaction is complete
• Model of the offered load of the transaction (packet size) and inter-arrival time of the requests is created with discrete random distributions
November 2009
Eldad Perahia, Intel Corporation
Slide 4
doc.: IEEE 802.11-09/1222r1
Submission
Transaction model• A transaction consists of a READ
request from host to drive for a specific block of data
• Followed by the data transfer from drive to host
• For the purpose of the model: – READ request is a short (256B) packet
sent from host to drive– Data transfer is instantaneous delivery
of 4kB – 128kB to transmit queue in drive to host direction
– Assume fixed 1ms delay between receipt of READ request and data offered
• In practice, delay varies based on seek latencies of drive
• Not a significant component of the model
READ (256B)
Data (4kB-128kB)Inter-arrival time
Inter-arrival time
November 2009
Eldad Perahia, Intel Corporation
Slide 5
doc.: IEEE 802.11-09/1222r1
Submission
Measured Transaction Size
• Most of the transaction are 64 Kbytes and 128 Kbytes
220 230 240 250 260 270 2800
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time (sec)
tran
sact
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size
(K
byte
)
measured data
0 20 40 60 80 100 120 1400
0.1
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0.6
0.7
data length (Kbytes)
Pro
babi
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of O
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ance
measured data
November 2009
Eldad Perahia, Intel Corporation
Slide 6
doc.: IEEE 802.11-09/1222r1
Submission
Measured Inter-Arrival Time of Requests
• Large grouping of inter-arrival times between 40usec and 1.1msec– Inter-arrival times of requests of 40usec indicate overlapping requests
• Also high frequency of inter-arrival times of 50msec– Probably due to operating system processing delay
220 230 240 250 260 270 2800
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time (sec)
Inte
r-ar
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(m
sec)
measured data
0 10 20 30 40 50 60 700
0.01
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inter-arrival time (msec)
Pro
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measured data
November 2009
Eldad Perahia, Intel Corporation
Slide 7
doc.: IEEE 802.11-09/1222r1
Submission
Data Rate of Measured Data based on Transaction Completion Time
• Maximum data rate equals 2.2 Gbps
• Average data rate (total transaction/total time) = 31 Mbps
220 230 240 250 260 270 2800
500
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time (sec)
Dat
a ra
te (
Mbp
s)
measured data
November 2009
Eldad Perahia, Intel Corporation
Slide 8
doc.: IEEE 802.11-09/1222r1
Submission
Model
• Step 1: Compute sequence of inter-arrival times of transaction requests
• Step 2: Compute corresponding sequence of transaction data sizes
November 2009
Eldad Perahia, Intel Corporation
Slide 9
doc.: IEEE 802.11-09/1222r1
Submission
Transaction Data Size Model
• Discrete Random Variable distribution
(4 ) 0.04
(32 ) 0.04
(64 ) 0.32
(96 ) 0.03
(128 ) 0.57
p KB
p KB
p KB
p KB
p KB
0 20 40 60 80 100 120 140
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
data length (Kbytes)
Pro
babi
lity
of O
ccur
ance
November 2009
Eldad Perahia, Intel Corporation
Slide 10
doc.: IEEE 802.11-09/1222r1
Submission
Inter-arrival Times of Transaction Requests Model
• Discrete Random Variable distribution
0 10 20 30 40 50 600
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
0.18
inter-arrival time (msec)
Pro
babi
lity
of O
ccur
ance
measured data
(0.04 ) 0.02
(0.5 ) 0.08
(0.6 ) 0.06
(0.7 ) 0.01
(0.8 ) 0.02
p ms
p ms
p ms
p ms
p ms
(49 ) 0.01
(50 ) 0.12
(51 ) 0.16
p ms
p ms
p ms
(0.9 ) 0.02
(1.0 ) 0.01
(1.1 ) 0.08
(1.5 ) 0.01
(2.0 ) 0.02
(4,5 12 ) 0.01
(18,19 ) 0.01
(25 ) 0.02
(29,30 43 ) 0.01
(44,45 48 ) 0.02
p ms
p ms
p ms
p ms
p ms
p ms
p ms
p ms
p ms
p ms
November 2009
Eldad Perahia, Intel Corporation
Slide 11
doc.: IEEE 802.11-09/1222r1
Submission
Simulated Inter-Arrival Time of Requests
• Simulated “time” is derived by a cumulative sum of the inter-arrival time
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time (sec)
Inte
r-ar
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sec)
simulated data
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time (sec)
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r-ar
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sec)
measured data
November 2009
Eldad Perahia, Intel Corporation
Slide 12
doc.: IEEE 802.11-09/1222r1
Submission
Simulated Transaction Size
• Simulated average data rate over the entire period is equal to 30Mbps
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time (sec)
tran
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size
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simulated data
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time (sec)
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size
(K
byte
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measured data
November 2009
Eldad Perahia, Intel Corporation
Slide 13
doc.: IEEE 802.11-09/1222r1
Submission
Conclusion
• Incorporate described hard disk drive model into Evaluation Methodology document