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Redundant Platter Data

Allow a hard drive to be configured at a fraction of its storage capacity to minimize seek times
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A mechanical hard drive is still a lot cheaper than an SSD, and often performance is more important than size. Proposed is a method of configuring a hard drive. (The circuitry on the drive would probably need to support this natively). A mechanical hard drive takes time to seek, rotate, and transfer data. In the proposed idea, the hard drive would be configured to delivery striped data from multiple heads simultaneously to increase throughput. (This is likely the case in the present technology.) The capacity would be cut in half or quartered to delivery data redundantly along paths spanning only 180 degrees or 90 degrees of the 360 degree track, making a 7200 rpm drive deliver the seek time of a 14400 rpm or 28800 rpm drive. (Writes would be a lot slower as a result, but this would be good for read-heavy environments.) The cylinders would likewise be redundant or even truncated to minimize fragmentation.
kevinthenerd, May 24 2012


       Random read performance may be improved somewhat, particularly if you staggered the tracks across the platter and the drive were smart enough to choose the shortest path taking into account both the time to move the head and the time to rotate the platter. But write performance would be abysmal. You'd be performing 2 or 4 physical writes to each platter for each logical write to the drive. I also suspect that sustained read performance would suffer, since you'd be seeking 2 or 4 times as often. [-]   

       Anyway, a technique already exists for achieving exactly the same goal. It's called "short stroking", where you partition the drive so it only uses, say, 10% of its capacity. The data is then written in a narrow band on each platter, so the total "stroke" of the heads is reduced considerably. Since the heads don't have to go nearly as far as they normally would, your average seek time is lowered considerably.
ytk, May 24 2012

       The big NAS and SAN devices already do something similar, just not at the single drive level. Basically, the stripe the data over several physical drives, so that there are 10 heads working, rather than just one. This increases read and write performance, as every file is striped this way. Not much improvement in seek times, but much much faster when actually reading and writing. And you don't lose any of the disks' capacity.
Carmi, May 25 2012

       Right, [Carmi], it's called RAID and it's hardly a new technology. What you're describing is a RAID 0 (or some other flavor that involves striping), and while it's useful to improve bandwidth, the idea here is to reduce latency, i.e. seek times. If anything, RAID striping will increase seek times, because the entire read/write operation has to wait for the last head to reach the data it needs.   

       It all comes down to the type of data you're accessing. If you're constantly making a lot of small changes to a database, your average seek time is going to be a critical factor in determining performance. On the other hand, if you're streaming large video files, seek time is basically irrelevant, and bandwidth is going to be key. I've seen reports that the low-RPM "green" drives perform as well or better in a RAID 0 configuration than the higher end 7200 or 10K RPM drives.
ytk, May 25 2012


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