Dell PowerVault MD3000i Tuning Manual page 18

Dell™ PowerVault MD3000 and MD3000i Array Tuning Best Practices
In addition, the stateCaptureData.txt file provides a more granular method for
determining the distribution of I/O within stripes and segments. In Figure 7 and
Figure 8, item 1 is the number of full stripes read and written, and item 2
indicates the number of full clusters or segments read or written. The value of
stripes per I/O request within reads and writes is also valuable for determining if
stripe or segment settings are optimal for the tested data access pattern. The
second generation firmware does not specifically break out the per-I/O ratio in
data output as the first generation firmware did, however it can still be manually
calculated simply by dividing the value in item 1 or 2 by the appropriate I/O
request value from item 3 indicated in Figure 8.
In most cases, best performance is achieved with segment and stripe per-I/O
ratios as close to 1.00. Traditionally, when tuning for maximal I/Os per second, if
the segments per-I/O ratio is high, the current segment size may be too low for
the application. Similarly, when tuning for highest possible data transfer rate, the
stripe per-I/O ratio should ideally be 1.00 or even multiples. If this value is high,
increasing the number of physical disks and/or the segment size can improve
performance.
Figure 7: First Generation Firmware– Stripe distribution. File: stateCaptureData.txt
Virtual Disk Unit 0 Configuration
Volume Type:
User Label:
Block Size:
Large IO:
Segment Size:
Stripe Size:
...
IO Statistics:
small
reads
requests 2028332119
blocks 3091968111 2518067526
avg blocks
IO pct. 93.21%
1.
reads 2028332119 2034477363
writes 147699066
write Full
algorithms 1105611
December 2008 – Revision A01
13+1 RAID 5
MyRAID5_1
512 bytes
4096 blocks
256 blocks
3328 blocks
small
writes
147699066
4 17
6.78%
IOs stripes
148449472
Partial
12598366 32120072
large large
reads writes
0 0 2176031185 1289775370
0 0 1315068341 4019884678
0 0
0.00% 0.00%
/IO clusters
1.00 2107869128
1.00 157404718
RMW No Parity
0
cache
total hits
0 3
0.00% 59.27%
/IO
1.03
2.
1.06
RMW2 FSWT
0 0
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