64 vs 32mb cache

[tury345]

What exactly does the cache of a HDD do?
Doing some research it would seem the consensus is that after 16mb you wont notice the difference but I wanted a second opinion.
On a computer using a 128gb SSD for the important programs (games/os/anything I use daily) would I even notice the difference in a 32mb cache vs a 64mb cache hard drive?
Newegg has a shellshocker for a 32mb cache 1tb HDD for $50 and im wondering if thats a good deal

 

[Pinhedd]

What exactly does the cache of a HDD do?
Doing some research it would seem the consensus is that after 16mb you wont notice the difference but I wanted a second opinion.
On a computer using a 128gb SSD for the important programs (games/os/anything I use daily) would I even notice the difference in a 32mb cache vs a 64mb cache hard drive?
Newegg has a shellshocker for a 32mb cache 1tb HDD for $50 and im wondering if thats a good deal

The hard drive buffer (cache is a bit of a misnomer) sits between the IO interface (SCSI/SAS/PATA/SATA/FC) and the disk platters.
The hard drive buffer allows for the drive to buffer a large number of read/write operations and execute them in one fell swoop when it is most appropriate to do so. The hard drive read heads can actually move quite a bit of data in a short period of time but only if the read head is in the location that it needs to be, which is almost never the case.

Since the hard drive platters rotate at a nominal RPM the read heads do not have the ability to access arbitrary physical sections of the disk in constant time, nor do they have the ability to pick up single sectors while ignoring all others. The disk buffer will be used to store sectors that are read before and after sectors that are requested by the operating system in case the OS decides that it needs them in short order. The disk buffer will also be used to store a sequence of write operations without actually completing them, allowing the disk to signal that the operations have been completed immediately even if the desired write location is on the other side of the platter.

 

[tury345]

The hard drive buffer (cache is a bit of a misnomer) sits between the IO interface (SCSI/SAS/PATA/SATA/FC) and the disk platters.
The hard drive buffer allows for the drive to buffer a large number of read/write operations and execute them in one fell swoop when it is most appropriate to do so. The hard drive read heads can actually move quite a bit of data in a short period of time but only if the read head is in the location that it needs to be, which is almost never the case.

Since the hard drive platters rotate at a nominal RPM the read heads do not have the ability to access arbitrary physical sections of the disk in constant time, nor do they have the ability to pick up single sectors while ignoring all others. The disk buffer will be used to store sectors that are read before and after sectors that are requested by the operating system in case the OS decides that it needs them in short order. The disk buffer will also be used to store a sequence of write operations without actually completing them, allowing the disk to signal that the operations have been completed immediately even if the desired write location is on the other side of the platter.

Thank you, that explains what it is very well. So am I correct in saying that a 64mb drive would be twice as fast, but only in the case that more than 64mb is needed? and in saying that the vast majority of cases would far exceed 64mb?
For example a huge 200mb mp3 file would load roughly twice as fast with a 64mb system?
If so thats quite a big deal

 

[inzone]

If your using a SSD as the OS drive then the other hard drives in the system would not need a large cache since they will just be used as storage. The drive with the OS on it would benefit from a large cache.

 

[Pinhedd]

Thank you, that explains what it is very well. So am I correct in saying that a 64mb drive would be twice as fast, but only in the case that more than 64mb is needed? and in saying that the vast majority of cases would far exceed 64mb?
For example a huge 200mb mp3 file would load roughly twice as fast with a 64mb system?
If so thats quite a big deal

64MiB would be preferable, but it would not be twice as fast except in extreme edge cases which are rarely seen in reality. A 64MiB buffer can hold twice as much data, but when the read head is in the right location the size of the buffer matters very little as the data will be streamed from the platter to the buffer, and from the buffer to the IO bus at the same rate, effectively marginalizing the buffer. The purpose of a buffer is to smooth out uneven operations on either side, such as when the read head is not yet in the write position, or has recently passed the position that was just requested.

32MB is plenty, especially if you have an SSD for your boot drive.

 

[tury345]

Best answer selected by tury345.