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Slow Disk I/O

I have a Dell 2850 with 8 gigabytes of ram and duel 2.80 Ghz, running under Server 64 bit Enterprize, with SQL 2005 64 bit. My disk I/O seems slow, I have 6 15K 146 gigabytes disks in raid 10 connected to a PERC 4e/Di as C drive, and the data and logs split between to arrays of 6 15K 146 gigabyte disks in raid 10 connect to a PERC 4/DC. Here are my numbers:
In memory read test
spidCallsmsCPUmsCallsPerSecRowsPerCallRowsPerSec
60254145300009328471.5 10 84715
6093704300009353123.46730 93704.01
6035069300009371168.967100 116896.7
60352730000938117.56671000 117566.7 Random I/O
spidCallsmsCPUmsCallsPerSecRowsPerCallRowsPerSecReadsPerSecRead MB/secAvg-sec/IO
613093001678110.294510102.9451200.32651.56514.9687
61194300169036.463220129.2644202.35871.58094.9254
616463001390421.524030645.7202751.67435.872511.9531
615533000086518.433350921.6667946.63347.395611.9289
61338300763111.23821001123.82001121.99108.765611.8584
6112830016244.26443001279.31801263.26009.869212.1472
614130406231.348410001348.41801286.851010.078712.1770
611931326360.606530001819.54301750.750013.71149.7875
61735250480.198699981985.50401880.340014.72659.3380 spidCallsmsCPUmsdpages/sMBTable MB/secReadsPerSecDisk MB/secAvg-sec/IO
57128428678714753.8232768115.2642234.7178115.46498.2660
57126022086816118.3032768125.9242256.1909126.143415.1261
If you have tempdb on those drives which are observing slow I/O, thenrefer to this blog and see this too to check whether you have enabled the online indexing in thsi case.

The read performance for an array of 6 15K drives connect directly connected to a PERC 4/DC controller seems very low, it is almost like somewhere it is throttled

Have you collected the SYSMON counters for further assessment, why not get checkout the hardware with the vendor.

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