Hard Drive Parts

I am going to Buy a new Hard Drive and I need help with one thing?

External Cache Memory is the Data that is held in the Hard Drive Memory before it goes to the Internal Cache Memory.

Then from the Internal Cache Memory it goes to the Hard Drive Plates.

I get all of this and how it works but I See the Hard Drives just Tell you the Cache Memory and this is it.

They Tell you one Number for the Cache and you do not know if it is for the Internal Cache Memory or the External Cache Memory.

Can anybody help?

 

Ummm, no. You are confused. There is no "internal" cache memory on hard drives.

Hard drives have a "buffer". This acts like cache and is located on the controller card mounted on the drive. That is the only cache or buffer a hard drive has.

When the OS calls for data saved on the drive, the read/write (R/W) head reads the data from the platters and it is temporarily stored in the drive's buffer until the OS needs it.

When the OS wants to save (write) data to the hard drive, it is temporarily saved in the drive's buffer, then saved (written) to disk.

Typically, the larger the buffer the better. Most HDs have 32MB or 64MB buffers these days. Less expensive drives may only have 8MB or even 2MB.

A "hybrid" drives (also called SSHD or solid state hard drive) uses NAND flash memory devices for the buffer - the same technology as SSDs. These offer better performance than normally buffered drives, but not as good as full SSDs.

 

If you are going to buy a mechanical HDD (as opposed to an SSD) make sure that you stay away from those which use Shingled Magnetic Recording (SMR) especially if this is going to be your boot drive

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Actually, when booting, most files are read in sequentially, so the impact with SMR disks there is minimal. This is especially true with the SATA 3.3 specification which came out in 2016 and features SMR optimized support.

To mitigate any disadvantage, ensure the drive has a large buffer and run with a decent supply of RAM (both of which you should do anyway). Writes take a bigger performance hit but again, that is mostly mitigated with a large buffer and lots of RAM.

SMR is not new. It is just appearing more often as a viable way to increase storage density on big drives as perpendicular magnetic recording (PMR) has reached its limits.

And like PMR drives, not all SMR drives are the same. Some are cheap, budget, poor performing. Others are not.

That said, SSD is still the way to go - if the budget allows.