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Random 8KB IOs per second
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| bet | 29/47 | | Sana | 30.03.2021 | | Hajmi | 1,33 Mb. | | #13789 |
Random 8KB IOs per second
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Dollars per KAPS
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Quantum Atlas 10K (10,000 RPM)
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105 read
105 write
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$5.09
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Quantum Fireball lct08 (5,400 RPM)
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66 read
90 write
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$3.17
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Table 9 – SCSI and IDE random IO performance.
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Indeed, when we tested a Maxtor 40GB DiamondMax™ drive that spins at 7200 RPM, we saw 107 random reads per second. This $250 drive comes closer to the random read performance of the 10K RPM SCSI drives. However, its write performance suffered with only 58 random writes per second. This is likely due to poor controller performance in the Maxtor hampering WCE write performance. In other tests we found that the Maxtor had poor performance on its outer 5GB as it was missing revolutions due to a slow controller. Performance improved on the inner bands as the media speed decreased and the controller was able to keep up.
With file system buffering, random IO performance, like sequential IO performance, is independent of request depth. For buffered reads and writes the file system serializes requests into one-deep requests. For buffered reads, the cache manager is apparently scheduling requests. With FS buffering, the number of IOs per second on reads doubled compared to a one deep unbuffered read. This is comparable to the gap on a single SCSI disk. The disk is spinning at 90 revolutions per second, and the disk is performing an average of 120 writes per second (see Figure 19). So, it seems that driver, controller, and drive are sorting the writes and achieving about 1.3 8KB IOs per revolution.
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