Here is a quick fix, which could take you a long time solving it even with Internet, because not so much information on the topic!
Let’s you want to run sysbench to check the IO of an SSD or NVME or your old hard drive? You run something like:
sysbench --test=fileio --file-total-size=4G --file-block-size=32K --file-num=128000 --num-threads=100 --max-requests=0 --max-time=300 --file-extra-flags=direct --file-test-mode=rndrd prepare sysbench --test=fileio --file-total-size=4G --file-block-size=32K --file-num=128000 --num-threads=100 --max-requests=0 --max-time=300 --file-extra-flags=direct --file-test-mode=rndrd run sysbench --test=fileio --file-total-size=4G --file-block-size=32K --file-num=128000 --num-threads=100 --max-requests=0 --max-time=300 --file-extra-flags=direct --file-test-mode=rndrd cleanup
Total of 4G files split in 128000 files and each file should be 32K seems OK at first, but you got:
FATAL: Too large position discovered in request
And the solution is simple enough:
file-total-size = file-num * file-block-size
And put the file-total-size in the units you used for file-block-size to be sure there are no rounding!
To put in simple words:
the size of file data should evenly divide by the number of files
So the above will transform to:
ssysbench --test=fileio --file-total-size=4096000K --file-block-size=32K --file-num=128000 --num-threads=100 --max-requests=0 --max-time=300 --file-extra-flags=direct --file-test-mode=rndrd prepare ssysbench --test=fileio --file-total-size=4096000K --file-block-size=32K --file-num=128000 --num-threads=100 --max-requests=0 --max-time=300 --file-extra-flags=direct --file-test-mode=rndrd run ssysbench --test=fileio --file-total-size=4096000K --file-block-size=32K --file-num=128000 --num-threads=100 --max-requests=0 --max-time=300 --file-extra-flags=direct --file-test-mode=rndrd cleanup
Here are the computes:
–file-total-size=4096000K = –file-num=128000 * –file-block-size=32K
Simple equation could save you a lot of time!
* Good run – no errors!
srv@local:/disks/1/test# sysbench --test=fileio --file-total-size=4096000K \
--file-block-size=32K --file-num=128000 --num-threads=100 --max-requests=0 \
--max-time=300 --file-extra-flags=direct --file-test-mode=rndrd prepare
sysbench 0.4.12: multi-threaded system evaluation benchmark
128000 files, 32Kb each, 4000Mb total
Creating files for the test...
srv@local:/disks/1/test# echo 3 > /proc/sys/vm/drop_caches
srv@local:/disks/1/test# sysbench --test=fileio --file-total-size=4096000K \
--file-block-size=32K --file-num=128000 --num-threads=100 --max-requests=0 \
--max-time=300 --file-extra-flags=direct --file-test-mode=rndrd run
sysbench 0.4.12: multi-threaded system evaluation benchmark
Running the test with following options:
Number of threads: 100
Extra file open flags: 16384
128000 files, 32Kb each
3.9062Gb total file size
Block size 32Kb
Number of random requests for random IO: 0
Read/Write ratio for combined random IO test: 1.50
Periodic FSYNC enabled, calling fsync() each 100 requests.
Calling fsync() at the end of test, Enabled.
Using synchronous I/O mode
Doing random read test
Threads started!
Time limit exceeded, exiting...
(last message repeated 99 times)
Done.
Operations performed: 4605591 Read, 0 Write, 0 Other = 4605591 Total
Read 140.55Gb Written 0b Total transferred 140.55Gb (479.74Mb/sec)
15351.63 Requests/sec executed
Test execution summary:
total time: 300.0067s
total number of events: 4605591
total time taken by event execution: 29893.5378
per-request statistics:
min: 0.07ms
avg: 6.49ms
max: 40.43ms
approx. 95 percentile: 7.06ms
Threads fairness:
events (avg/stddev): 46055.9100/51.84
execution time (avg/stddev): 298.9354/0.00
sysbench 0.4.12: multi-threaded system evaluation benchmark
srv@local:/disks/1/test# sysbench --test=fileio --file-total-size=4096000K \
--file-block-size=32K --file-num=128000 --num-threads=100 --max-requests=0 \
--max-time=300 --file-extra-flags=direct --file-test-mode=rndrd run
Removing test files...
* Bad run – with the error: FATAL: Too large position discovered in request
srv@local:/disks/1/test# sysbench --test=fileio --file-total-size=4096M \
--file-block-size=32K --file-num=128000 --num-threads=100 --max-requests=0 \
--max-time=300 --file-extra-flags=direct --file-test-mode=rndrd prepare
sysbench 0.4.12: multi-threaded system evaluation benchmark
128000 files, 32Kb each, 4096M total
Creating files for the test...
srv@local:/disks/1/test# echo 3 > /proc/sys/vm/drop_caches
srv@local:/disks/1/test# sysbench --test=fileio --file-total-size=4096M \
--file-block-size=32K --file-num=128000 --num-threads=100 --max-requests=0 \
--max-time=300 --file-extra-flags=direct --file-test-mode=rndrd run
sysbench 0.4.12: multi-threaded system evaluation benchmark
Running the test with following options:
Number of threads: 100
Extra file open flags: 16384
128000 files, 32.768Kb each
3.9999Gb total file size
Block size 32Kb
Number of random requests for random IO: 200000
Read/Write ratio for combined random IO test: 1.50
Periodic FSYNC enabled, calling fsync() each 100 requests.
Calling fsync() at the end of test, Enabled.
Using synchronous I/O mode
Doing random read test
Threads started!
FATAL: Too large position discovered in request!
(last message repeated 30 times)
FATAL: Failed to read file! file: 80714 pos: 2 errno = 22 ()
FATAL: Too large position discovered in request!
(last message repeated 67 times)
Done.
Operations performed: 1 Read, 0 Write, 0 Other = 1 Total
Read 32Kb Written 0b Total transferred 32Kb (114.71Kb/sec)
3.58 Requests/sec executed
Test execution summary:
total time: 0.2790s
total number of events: 1
total time taken by event execution: 0.0038
per-request statistics:
min: 3.79ms
avg: 3.79ms
max: 3.79ms
approx. 95 percentile: 10000000.00ms
Threads fairness:
events (avg/stddev): 0.0100/0.10
execution time (avg/stddev): 0.0000/0.00
srv@local:/disks/1/test# sysbench --test=fileio --file-total-size=4096M \
--file-block-size=32K --file-num=128000 --num-threads=100 --max-requests=0 \
--max-time=300 --file-extra-flags=direct --file-test-mode=rndrd cleanup
Removing test files...