At 50 MB/s, an entire CD's worth of data can be handled in about 14 seconds.ĭefragmenting frequently speeds up your computer on the order of nanoseconds, and frequent defragmentation will cause platter defects sooner. Typical modern hard drive transfer rates are between 30 to 50 megabytes per second. Combining these things (and more that I haven't even mentioned) gives you a nice representation of the speed you are dealing with.
Now, drives are loaded with up to 16 MB of cache.įinally, most modern operating systems have lazy write features where the OS can defer disk writes until an appropriate time (like when the bus and CPU are not so congested). (I had ghosted my drive to a new one - I got to see the difference immediately after the ghost, and it was very obvious).
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I personally have gone from 0 cache to 8 MB of cache and just a simple bootup of Windows was stunningly fast. The bigger the cache your drive has, the more apparent this effect is. By the time the computer sends the request for the next section of data, the drive is ready to pass the section from its internal buffer back to the bus. Next, you have to take into account the internal RAM that modern drives have, and their new "lookahead" features that allow the drive to read data into the buffer in anticipation of a data request. Pretty sick, huh? Not to mention that there are multiple heads reading multiple platters. But I know it's faster than a blink.Ī hard drive head is typically 0.3 by 1.2 millimeters. I would guess that the travel time from the inner zone to the outer, or vice versa, is probably around 20-25 milliseconds (I don't have a source for that data, that's just my guess). The inner zone has quicker seek time because it is a shorter circumference, and the outermost zone of the platter has a much greater circumference. The typical access time from random sector to random sector is between 5 to 15 milliseconds because of the great speed at which it spins, combined with the precision servo motor controlling the head and actuator, and then depending on which zone of the platter the heads are in. You can pick up a drive that is spinning that fast, and while holding it horizontally, tilt it left and right and feel the G-force it gives off. Left unchecked, help desk personnel can squander valuable hours combating performance problems that are a direct or an indirect result of disk fragmentation.Well, most drives spin at 7200 RPM (some more, some less) which is enough to make the drive fight gravity. in Conshohocken, Pa., quantifies the performance repercussions of fragmentation, finding gains of 20% to 219% following defragmentation, depending on the degree of fragmentation and the applications being tested.
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"File fragmentation is a primary reason for the gradual degradation of system performance and the specific cause of longer reads and extended reboots," says Microsoft Corp.'s Michael Kessler in a paper titled "Maintaining Windows 2000 Peak Performance Through Defragmentation."Ī study by National Software Testing Labs Inc. These servers experienced a significant degradation in performance because each fragment requires a separate disk I/O process. Half of the respondents discovered files split into between 2,000 and 10,000 fragments, and another 33% had files fragmented into between 10,001 and 95,000 pieces. An even greater degree of fragmentation existed for servers.