Hard Drive Performance Question

[mattyb240]

I was having a conversation at work, and basically I wanted it settled.

We were discussing hard drives as my friend is replacing his laptop drive, this got onto capacities and performances.

As capacity increases does performance suffer? They believe a 160gb drive (example) would be faster than a 1tb drive. Assuming both were the same manufacturer, rpm, and interface is this true?

Can anyone elaborate please? Everything I have googled including looking at hard drive specs seem to support my side as far as read/write times and latency etc?

Sorry for the random posting!

Matt:D

[In2Photos]

Usually the larger drives perform better as the data is closer together and the spindle does not have to travel as far. Better yet just pick up an SSD and wipe the floor with the HDD. ;)

[mattyb240]

Usually the larger drives perform better as the data is closer together and the spindle does not have to travel as far. Better yet just pick up an SSD and wipe the floor with the HDD. ;)

I know it was a general discussion, but unfortunately I don't know the technical innards, but there argument seemed flawed.

[MaxxuM]

Nope, he's right. The more dense the HDD the less heads have to move to get data. If you had a 120GB HDD at 7200RPM it will be slower (data transfer) than a 1TB HDD at 5400RPM. Add to this that the larger the drive the more advanced they will be since larger HDDs use newer tech than 120GB drives.

[mattyb240]

Nope, he's right. The more dense the HDD the less heads have to move to get data. If you had a 120GB HDD at 7200RPM it will be slower (data transfer) than a 1TB HDD at 5400RPM. Add to this that the larger the drive the more advanced they will be since larger HDDs use newer tech than 120GB drives.

So I am right? The capacity does not get "slower" as it increases? This was basically the argument, including SD cards as well…..

[MaxxuM]

So I am right? The capacity does not get "slower" as it increases? This was basically the argument, including SD cards as well…..

Capacity is a measure of how much something can hold and slower describes speed. HDD 'speed' is measured in several ways: spindle speed (RPMs), seek (ms), read/write (mb/s) and so on. RPM is usually a constant (i.e. 7200RPM or 5400RPM). This does not measure data movement. That would be read/write speeds. Seek times measure the time it takes the HDD's head to find the data. Seek times are measured as a 'delay'. Drive capacity is measured in bytes. The more data that can be squeezed into a single inch has been increasing every year. The more dense (capacity) a drive has the less a HDD read/write head has to move to reach that data.

So, it is more than just a trend when I say that the larger the capacity of the drive the more likely it will be able to move more data in a shorter amount of time. There are some exceptions (like Velociraptors, 10,000RPM drives, SSD's and so on).

[mattyb240]

Thanks Maxxum I value your detailed input, upon more googling I have found more information about the details you list! Hopefully I will be able to go in tomorrows discussion with a few more facts and bench marks!

[Tony-S]

Perhaps most important is platter density. WD can put 375 GB on a platter (187.5 GB per side) and this is what's used in their 750 GB 2.5" drive. They use three of these in their 1 TB drive (which is 12.5mm high).

[tim]

As platters get more dense, given the same disk velocity, more data passes under the read head per second so the data comes back faster. If the read head has to move, say to get a different file, that can be slow.

With an SSD/SD card there's no read head so there's less latency, but the throughput isn't a lot higher.

There are hybrid drives now, and most used data (usually the OS) is cached in flash memory on the disk. They're meant to be great value, much faster for common stuff like booting or launching programs, and as fast as a normal disk otherwise.

[Tony-S]

As platters get more dense, given the same disk velocity, more data passes under the read head per second so the data comes back faster.

This is also why 3.5" drives usually perform better. The outer edge is further away, thus greater speed (at the same rpm).

[canonloader]

Better yet just pick up an SSD and wipe the floor with the HDD.
I have been trying to find more information on these drives. Actually, I have been talking about them for years with my brother, who was into development of solid state processing decades ago. I can find them for sale now, but there seems to be no information on how you would hook one up in your tower, or what you need to use it as a base for the OS. Can you install windows on one?

[tim]

I have been trying to find more information on these drives. Actually, I have been talking about them for years with my brother, who was into development of solid state processing decades ago. I can find them for sale now, but there seems to be no information on how you would hook one up in your tower, or what you need to use it as a base for the OS. Can you install windows on one?

They look like a normal hard drive to the computer, you can install windows or anything you like on them.

[canonloader]

I read that they have to be DMA capable though to take an OS, and I'm not sure exactly what that means, and have not seen "DMA capable" on any of the advertised statistics for them. For instance, is a CF card DMA capable?

[tim]

You're overthinking this. They work like a normal hard drive.

[canonloader]

HAHA, I've found that it's much better to over think than over pay. LOL

[Hen3Ry]

Capacity is a measure of how much something can hold and slower describes speed. HDD 'speed' is measured in several ways: spindle speed (RPMs), seek (ms), read/write (mb/s) and so on. RPM is usually a constant (i.e. 7200RPM or 5400RPM). This does not measure data movement. That would be read/write speeds. Seek times measure the time it takes the HDD's head to find the data. Seek times are measured as a 'delay'. Drive capacity is measured in bytes. The more data that can be squeezed into a single inch has been increasing every year. The more dense (capacity) a drive has the less a HDD read/write head has to move to reach that data.

So, it is more than just a trend when I say that the larger the capacity of the drive the more likely it will be able to move more data in a shorter amount of time. There are some exceptions (like Velociraptors, 10,000RPM drives, SSD's and so on).

This is an excellent description, as far it it goes, but it ignores a couple of important components in I/O service time. A disk platter is divided into concentric tracks, and the tracks are divided into sectors, the number of which vary with the density of the drive - obviously, the outer tracks on a disk platter are much longer than the tracks at the center, and have more sectors. So, after Seeking the track, the drive has to do a Set Sector which defines where on the track the data is. Once it has done that, it can begin reading. The denser the drive is, the faster it can read, given the same rotation speed. A faster rotation will obviously read data faster than a slower drive, assuming the density is equal.

Now the second factor comes into play, which is drive fragmentation. If the drive is completely unfragmented, it will have to do only Set Sectors until it exhaust the data on that track and its sectors, then it does another Seek and continues setting sectors and reading. If, however, the file/drive is fragmented, it may have to do a Seek for every Set Sector. This can greatly increase I/O Service time, especially with large files.

[CyberDyneSystems]

We need to clarify with the "all else being equal" aspect,. but yes, absolutely given identical tech in other aspects, higher aerial density of a drive means more data under the head in a shorter amount of time.

So the absolute rule of thumb is large drive, faster speed. In addition, larger drive also usually means newer drive, thus even more boost as it is likely to have more advanced technology elsewhere.

The source of your friends confusion is likely the WD Raptor series.
Way back wehn the 32GB version was introduced, it was the only (reasonably priced) drive with it's 10K rotational speed. To get that speed it had to reduce platter size, and thus room for data, and thus capacity.
In it's day, the WD Raptors were always the fastest consumer oriented drives,. for many years in fact.
But "all else was far from equal" the additional rotational speed was the boost in this case, but that additional speed was solely found in this one series of drive. It was not a "rule of thumb", in fact it bucked the trend.

With few exceptions, larger drives are faster, and thus as capacity has increased over the years, so has speed.