While shopping around for a new hard drive, I\'ve noticed that one of the features mentioned on all the boxes is the size of the hard drive\'s cache.
I\'m a little confused--I\'m not sure how a hard drive can have a cache--and wondering if I should get the hard drive with the largest cache possible for giga and for playing samples in general. (I\'m also a little puzzled by the small size of the caches. Some are 2 megs, some 8 megs. Assuming this is some kind of RAM cache, not much, given the size of today\'s files.)
Hi Jake, my understanding is that the data is collected from the drive into a buffer (cache) on the hard drive and then sent to the ram. I\'m not sure why really, but I guess simple logic dictates that a larger cache equals fewer trips back and forward and hence better performance.
Actually here is the Tech Target definition;
A disk cache is a mechanism for improving the time it takes to read from or write to a hard disk. Today, the disk cache is usually included as part of the hard disk. A disk cache can also be a specified portion of random access memory (RAM). The disk cache holds data that has recently been read and, in some cases, adjacent data areas that are likely to be accessed next. Write caching is also provided with some disk caches.
The other type of hardware cache inside your computer is cache memory.
After reading that I\'m thinking perhaps that hard drive caches were built so that ram didnt get used.
A physical hard drive cache can speed up transfers of small files that you are accessing a lot. Hard drive caches are optimized more for reading random data whereas an operating system cache is optimized more for high data transfer rates.
For Gigastudio, the difference in performance between a hard drive with a 2MB cache and an 8MB cache is negligible. Your most significant factor is always read seek times. That\'s why we always go with Hitachi drives in our systems -- they have the lowest seek times of all the parallel IDE drives.
In general, a larger cache in a hard drive does indeed improve performance. As stated elsewhere in this thread, average seek time is more important for Giga than cache size, but the larger cache size can still help. Think of it this way: If you go to the grocery store, you can carry more in a shopping cart than you can carry in your arms. If you\'re retrieving a large number of items, the cart cuts down on the number of trips you have to make to the checkout counter.
It\'s the same with a cache on a hard drive. The DMA controller is responsible for transferring the contents of the cache to your computer\'s RAM. Some number of physical operations must be carried out by that controller to make the transfer. Typically, it\'s little or no more expensive for the controller to transfer 8MB than it is to transfer 2MB. Fewer transfers equals faster performance.
But again, the faster seek time is more important for Giga because these transfers typically take less than 1ms. This means that spending an extra 5ms finding a sector on the hard drive can be as expensive as dozens of DMA transfers.