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тАО04-22-2003 05:03 AM
тАО04-22-2003 05:03 AM
Solved! Go to Solution.
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тАО04-22-2003 05:31 AM
тАО04-22-2003 05:31 AM
SolutionHow it works is when you begin to pass that 50% mark (50% of total raw storage allocated as LUNs), the VA begins to "make room" for the LUN space over 50% by converting some of the RAID 0/1 to RAID 5DP. How much it converts depends on the above factors.
Since RAID 5DP can be quite a bit slower than RAID 0/1 in some cases (such as small block random writes), the more data it converts to RAID 5DP, the more you will see effects in your performance.
In theory, you should not see a large difference in performance if you do not go very far above 50%, as the RAID-5DP portion of the data will be relatively small, and the VA picks data blocks to be RAID-5DP based on access patterns - the least-used data blocks will be converted to RAID-5DP first.
It's a performance-for-capacity trade-off.
Good luck!
Vince
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тАО04-22-2003 05:43 AM
тАО04-22-2003 05:43 AM
Re: Performance hit going from RAID 0/1 to RAID 5DP
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тАО04-22-2003 06:53 AM
тАО04-22-2003 06:53 AM
Re: Performance hit going from RAID 0/1 to RAID 5DP
I would continue a bit where Vincent finished a correct explanation of AutoRAID. The most important thing is that the least used data is moved to R5DP only, as Vincent says. So, it is data that has not been touched for the longest time. R5DP has a very similar performance for reading as R0+1 has, so You should not notice a performance hit (and, You have a cache there for quick rewrites), if You are up to some 75% used capacity. Quite clever. Vladimir
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тАО04-22-2003 07:32 PM
тАО04-22-2003 07:32 PM
Re: Performance hit going from RAID 0/1 to RAID 5DP
Is yours so?
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тАО04-22-2003 07:55 PM
тАО04-22-2003 07:55 PM
Re: Performance hit going from RAID 0/1 to RAID 5DP
Once you???ve sure there is no hardware problem, then most likely cause of performance problems in the AutoRAID setting is due to the workload. If the workload is consistently high demand and the workload contains a signification write content (~>50%) then (typically) the AutoRAID polices can???t keep up. This can be verified by reviewing the internal performance statistics. See the armperf OPAQUE and RAID 5DP to RAID 5DP activity. (the AutoRAID policies are background tasks??? if there is no background time, then they can???t run).
This would be an indicator that your workload is a candidate for RAID 1+0 operation. If you reply with the exact disk configuration (number and sizes), I???ll reply with the maximum LUN capacity to create a RAID 1+0 only array ??? it???s not exactly 50% of anything!