MSA1000 RAID6 / RAID5 Migrate

[Miika T]

I have MSA1000 with fw 7.00 and 14x146Gb drives in one Array. Multiple luns all with RAID6. Due to one MSC cluster write cache is being disabled, which currently results in horrible write performance. I did create one Raid5 lun in the same array, which seems to perform better than raid6 (adg) lun's. Does anyone have any facts on the overall perfomance, if I do have both raid6 and raid5 luns in the same array (during the migration phase)? Will there be a performance impact on both types of luns?

-Miika

[Víctor Cespón]

RAID ADG has to write 2 sets of parity information for each set of data, so it's slower than RAID 5, that only writes one.

You can see some performance results here:

http://h20000.www2.hp.com/bc/docs/support/SupportManual/c00502620/c00502620.pdf

[Miika T]

I know the perfomance issue between raid5 and raid6, but I was more concerned about the issue if MSA can actually do raid5 and raid6 on the same array. Basically will raid5 work at the same performance level as a lun in an array which only has raid5 luns in it, or will it actually be slower as there are raid6 lun's the same array at the same time (controller needs to do more work).

-Miika

[Víctor Cespón]

Will run a little slower. Writing on a RAID 6 requires one more I/O operation and one parity calculation more than writing on a RAID 5.