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Performance measurements from a single Thor
To be able to make long-term calculations about bandwidth requirements in the Phoenix Cluster we need an accurate and round number to work with, when talking about how much data bandwidth can a Thor give.
Disk layout
- There are 5 Raid6 arrays made of 7+2 disks, and three spare disks
- Those five arrays are joined together in a volume group, then a logical volume, and then a xfs filesystem
- All with default values.
Performance
The disk performance to be around 700 MB/s using Bonnie++
Then, we tried to measure how much the clients can get out of it. We use dccp transfers to /dev/null
- With 2 wn, 15 or 20 transfers per WN, we get 450 MB/s
- Above that, even with 90 transfers per WN, we get 500 MB/s.
- One single WN with 45 transfers gets only 310 MB/s
- Putting three WNs doesn't increase the 500 MB/s boundary
- The write speed for one WN and 45 transfers at the same time is 70 MB/s
All in all, we can determine that each Thor can serve up to
500 MB/s read speed to the clients.
Another disk layout - with raid0
We realised that, from a single transfer, you only access one of the five raid6s. That's because creating a volume group is not the same as creating a stripped raid0 (looks like it creates a jbod). So, we tried making a raid0 on top of all raid6s. The rest is the same as before
Performance
- Write speed, from 2 WNs and 23 transfers each, we get 270 MB/s write speed peaks.
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