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Joe Chang

Dell PERC6 RAID Controller Performance

Last month, Scott pointed out the really bad performance characteristics of the Dell PERC6 in RAID0 sequential write, particularly compared with RAID-5. Granted, this is not necessarily a red flag because few people use RAID 0 in production. Still, if one can't write code or test correctly, one should not be in the hardware/firmware business. Dell recently released firmware 6.1.1, the previous was 6.0.3. The driver was updated from 2.20 to 2.23.

My results for 2 x 4 disk RAID0 arrays on PERC6, writing to another PERC6 with same disks.

Large block Read test: 690-713 MB/sec

SQL Server backup test 

Old 6.0.3 firmware:         81MB/sec Write-Back    129MB/sec Write-Thru

New 6.1.1 firmware:        354MB/s Write-Back      631MB/sec Write-Thru

The old driver with new firmware has the same results as new driver with new firmware, so this was really a firmware issue. The old PERC5 did not have as bad RAID 0 write performance as the PERC6 with old firmware. Random write IO testing shows mixed results between write-thru and write back, some favoring WT, some WB but not by a large amount.

A curious note. The Dell TPC-E report for the R900 with 4 x Xeon X7460 used the LSI MegaRAID SAS 8888ELP controllers, not the PERC6E (there was a PERC6i for internal drives). Both PERC6 and LSI 8888 use LSI components (and common drivers?)

Published Wednesday, October 01, 2008 9:36 AM by jchang

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Caleb B said:

6.1.1 (A07) was recalled a few days ago due to a problem with arrays of greater than 8 Disks.

The new 6.1.1 (A08) was re-released today.

Thanks Joe!

October 17, 2008 6:29 PM

jchang said:

thanks Caleb, I will retest with A08 when I get back from Europe

October 18, 2008 2:59 AM

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About jchang

Reverse engineering the SQL Server Cost Based Optimizer (Query Optimizer), NUMA System Architecture, performance tools developer - SQL ExecStats, mucking with the data distribution statistics histogram - decoding STATS_STREAM, Parallel Execution plans, microprocessors, SSD, HDD, SAN, storage performance, performance modeling and prediction, database architecture, SQL Server engine

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