5400rpm v 7200rpm

[Eric2]

Looking to update one of my MacPro bays that hold all my music files. My operating system and iTunes are on a different bay.

 

I’m looking for a 2TB HD and made a shortlist of the new Western Digital Caviar Black or Western Digital Green Power RE4.

 

Which one would you recommend?

 

Both have 64MB Cache and are a similar price.

 

I’m not using the HD for raid but the Green RE4 has the advantage of being slightly quieter and believe the RE models are more reliable.

 

The advantage of the Black is it runs at 7200rpm which makes it faster. SSD are highly thought of here so wondered whether the 5400 (Green) v 7200rpm (Black) would make a difference?

 

Thanks

 

 

[PeterSt]

Hi,

 

SSDs are not fast for their "burst" capabilities, but for their access times (just where the HDD is slow at).

 

The rotation speed of an HDD is about the burst speed, and if you have non-scattered audio data it can matter. Why "can" ?

 

Because if you put something in between other than SATAII (or III) you will loose on that slow bottleneck. IOW :

Only when the playback software is in the same housing as the HDD you may notice it. However, even in that case you'd need a burst operation to notice it, and any normal audio player doesn't use that (XXHE does because of reading the whole track into memory, but that's for Windows).

 

When you'd make a backup of the whole HDD it will be about as much slower as the rev ratio tells you. But here too : only if the backup is being done over a fast enough connection not to be a bottleneck (like SATAII).

 

Personally I wouldn't bother much !

Peter

 

[Eric2]

Hi Peter,

 

Thanks for the reply. Although you’ve lost me slightly!

 

Just to be clear I already use 2 HDD. The one containing OSX and iTunes will not change (or at least not in the short term).

The 2nd internal HDD is already in use but I’m going to run out of space soon so plan to swop the old 1TB HDD with a 2TB one.

 

From your reply I think your saying the access time is the most important? If this is the case a 7200 HD will read quicker than a 5400 drive, so does this not have an advantage?

 

Or are you saying that it doesn’t really matter as its the speed from the HD that contains iTunes and OSX that makes the difference. The 2nd HDD containing the music will have little or no impact at all in this configuration?

 

[PeterSt]

Hi Eric,

 

Net, indeed it is about the access time, because the other matters (the bulk put through) can't be utilized as per my before post. And, the revs hardly (or don't) influence the access time.

 

Access time is about the positioning if the disk head, which is somewhere in between the outmost and innermost (circular) boundary of the disk.

The revs is about the speed the data surface moves under the head. The more revs the larger that speed (but also : the higher the density (= disk capacity) the more data can/will be read within a time frame.

 

The access time hardly has changed in 30 years time. This is also related to the density (but now from inner to outer circle). However, with SSDs the access time has been drastically reduced because of no head positioning being in order (it's all direct access). The throughput of an SSD though, is not as high as a faster rotating disk. This is because ... now think ... each adjacent memory cell needs a kind of access time again. Not so with harddisks (if the data is nicely adjacent hence not scattered), because there the throughput just is determined by the velocity of the surface of the disk under the head.

If you'd know how much data one circle (named a cylinder) contains, you can easily calculate the amount of data read per second by incorporating the revs (like 7200/60 = 120 revolutions per second).

 

What not many people see through, is that obtaining a disk of 10 times the size needed, implies an access time of 1/10th of the average access time rate of the disk (think about that too). Generally for database systems this means just 10 times faster. Sadly our audio disks are always full, so we won't gain much on such an idea.

 

If this is clear a bit now, you can also see that using an SSD for holding audio data is of no use when it comes to speed. It's only more slow. However, using the SSD for holding a representative of the audio data (in meta data) for fast lookup, *that* is 5-10 times more fast (maybe too difficult to explain, but XXHE does just that and for example coughs up 200,000 tracks in 0.2 seconds or so. Including coverart).

 

But don't forget : if you have no real bottleneck and SATAII for your net (opposed to gross) connection (meaning not using ethernet, wireless etc. etc.) *then* the revs start to count just the same. If a full track has to be loaded in one go (again, like XXHE wants it) it is a matter of 0.54 seconds agains 0.72 seconds (to name something, but mind the proper ratio) and the access time is minor (because only needed once *IF* the data is not scattered). Now, there is no player that works like this for the Mac, so you won't care about that.

 

Clear a little (in my dutch) ?

Peter

 

[cfmsp]

 

I bought a 500 Gb Caviar Green internal disk for my Powermac G5 recently, along with it's eternal equivalent, the Mybook Studio II.

 

I chose the Caviar Green on a hunch that the lower AC/power reqts, less noise, less heat were more likely to pay off as compared to the higher performing Caviar Black series, esp. as an internal disk.

 

I chose the 1Tb Mybook (two 500Gb disks) after reading reports that WD has a higher failure rate on the larger disks at this time, although I wasn't that concerned about it. If I didn't already have multiple 1Tb disks available, I'd have gotten the 2Tb.

 

clay

 

 

 

 

[Eric2]

Peter that’s much clearer thank you your time in explaining. Much appreciated.