Oliver,
Thanks for the info.
We then run sysbench for random IO testing, the result is even worse
(757 KB/s).
each object has 3 replicas.
Both networks are 10Gbps, I don't think there are issues with network.
Maybe lacking of SSD cache, and miscorrect configure to the cluster are
the reason.
----
Extra file open flags: 0
128 files, 360Mb each
45Gb total file size
Block size 16Kb
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 r/w test
Threads started!
Time limit exceeded, exiting...
Done.
Operations performed: 8520 Read, 5680 Write, 18056 Other = 32256 Total
Read 133.12Mb Written 88.75Mb Total transferred 221.88Mb (757.33Kb/sec)
47.33 Requests/sec executed
Test execution summary:
total time: 300.0012s
total number of events: 14200
total time taken by event execution: 21.6865
per-request statistics:
min: 0.02ms
avg: 1.53ms
max: 1325.73ms
approx. 95 percentile: 1.92ms
Threads fairness:
events (avg/stddev): 14200.0000/0.00
execution time (avg/stddev): 21.6865/0.00
On 2016/5/19 星期四 18:24, Oliver Dzombic wrote:
Hi Ken,
dd is ok, but you should consider the fact that dd is a squence of writing.
So if you have random writes in your later productive usage, then this
test is basically only good to meassure the maximum squential write
performance in idle state.
And 250 MB for 200 HDD's is quiet evil bad as a performance for a
sequential write.
Sequential write of a 7200 RPM SATA HDD should be around 70-100 MB,
maybe more.
So if you have 200 of them, idle, and writing a sequence, and resulting
in 250 MB/s. That does not look good to me.
So eighter your network is not good, or your settings are not good. Or
you have too high replica number or something like that.
At least for me, 200x HDDs and each HDD deliver 1,2 MB/s writing speed
performance.
I assume that your 4 GB won't be spread over all 200 HDDs. But still,
the result does not look like good performance.
FIO is a nice test with different settings.
---
The effect of conv=fdatasync will be only as big, as the RAM memory of
your test client will be.
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