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4291
July 26th, 2016 10:00
PERC H730 Mini + SSD write policy configuration problem
We are using Dell R430 servers with PERC H730 Mini raid controller with 4 SSD disks attached. Every disk attached as separate RAID0 device. And we run aerospike database on this servers.
We tried to configure disk system according to aerospike manuals but perfomance was bad - read latency was very high with big spikes every 10-30 seconds. But when I turned on WriteBack policy on - everything became good even on read only tests.
How can write caching policy affect read performance in read only tests?
According to every manual of configuring ssd disks with raid controllers write policy should be set to WriteThrough, but in our configuration it doesnt work.
We also tried to attach our disks in HBA mode and again got same performance as in case when write policy was set to WriteThrough.
And we tried to use Intel SSD disks and Dell SSD disks and there were no difference in tests. Behavior was the same. So we made conclusion that problem is in raid controller.
Can somebody explain that behavior?
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agnek
3 Posts
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July 27th, 2016 13:00
Hello.
Every disk in our system attached as separate RAID0 virtual disk. And we also tried to attach them in HBA mode.
We have made our performance only with act tool ( github.com/.../act ). And this tool was the only source of IO. Same effect we saw on production nodes with aerospike server. When we turned on WriteBack - performance increased.
And we also tried to change write policy while our tests were running using iDRAC and saw same behavior. When we turn on WriteBack - latency is acceptable, when we turn on WriteThrough - latency in unacceptable.
agnek
3 Posts
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July 27th, 2016 13:00
No, we used hardware raid.