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alex_kac · Feb 28, 2007, 12:06 AM

Parallels runs dramatically faster for me off my external FW800 7200RPM drive and I'm sure it would run even faster using eSATA. My MBP 17 has the 5400 120GB drive.

Now I am waiting for the next MBP with Leopard on it (I don't care if its the current one with Leopard - I'm just waiting for Leopard) and I think 'm going to go with a 7200 RPM drive on it. The question is does a 7200 RPM desktop drive run faster than a laptop 7200 RPm drive? Can I expect to see same speed increase if not better (since its on the internal SATA bus)?

mduell · Feb 28, 2007, 12:56 AM

Yes, the 7200RPM desktop drives are faster than the 7200RPM laptop drives. Depends on the capacities you're comparing and what you're doing, but as a rule of thumb I'd say 2-3x faster.

brokenjago · Feb 28, 2007, 02:14 AM

Why are desktop drives at the same RPM faster than laptop ones?

mduell · Feb 28, 2007, 01:02 PM

They're physically bigger.

And they can "afford" (in the heat sense) more power hungry electronics, but I doubt that's as big of a factor.

alex_kac · Feb 28, 2007, 01:18 PM

True they are physically bigger, but at the same time that can mean they can get to data faster because less travel time is required. I haven't seen any stats on this, has anyone else seen these things benchmarked?

ghporter · Feb 28, 2007, 01:51 PM

I would have thought that smaller platter diameters would make it faster to move heads to the needed track/sector to read or write data. What onboard electronics in a desktop drive help it go faster?

olePigeon · Feb 28, 2007, 02:41 PM

Alas, 15K RPM SAS laptop drives are the fastest on the market.

Unfortunately, there's not a single Apple portable that can take Serial Attached SCSI. Would be awesome, though.

alex_kac · Feb 28, 2007, 03:53 PM

Well yes....but we are talking about reality here

mduell · Feb 28, 2007, 07:05 PM

Originally Posted by alex_kac

True they are physically bigger, but at the same time that can mean they can get to data faster because less travel time is required. I haven't seen any stats on this, has anyone else seen these things benchmarked?

Same angular speed * larger radius = higher linear velocity
With the same data density, that means higher read/write speeds.

Originally Posted by ghporter

I would have thought that smaller platter diameters would make it faster to move heads to the needed track/sector to read or write data. What onboard electronics in a desktop drive help it go faster?

Head movement time isn't usually the limiting factor and the usable part of the 2.5" and 3.5" platters is about the same width.

The electronic controller onboard the drive can be bigger and use more power, which may help with transfer speeds.

brokenjago · Mar 1, 2007, 02:09 AM

But 2-3x more transfer speeds?

mduell · Mar 1, 2007, 01:02 PM

Originally Posted by brokenjago

But 2-3x more transfer speeds?

7200RPM 3.5" drives can sustain 70-80MBps and 35-45MBps min.

7200RPM 2.5" drives can sustain 30-50MBps max and 20-30MBps min.

For random reads the spread is a little wider.

olePigeon · Mar 1, 2007, 02:10 PM

Originally Posted by mduell

7200RPM 3.5" drives can sustain 70-80MBps and 35-45MBps min.

7200RPM 2.5" drives can sustain 30-50MBps max and 20-30MBps min.

For random reads the spread is a little wider.

I reject reality, and insert my own! In fantasy land where MacBook Pros have 2.5" SAS drives, they get:

15000 RPM 2.5" with 3Gb/sec interface and sustained 119.84 to 199.78 MB/sec throughput.

http://www.seagate.com/docs/pdf/data...etah_15k_5.pdf
Seagate introduces 15K rpm 2.5" hard drive | TG Daily

Oh how I miss SCSI.

mduell · Mar 1, 2007, 04:50 PM

Originally Posted by olePigeon

I reject reality, and insert my own! In fantasy land where MacBook Pros have 2.5" SAS drives, they get:

15000 RPM 2.5" with 3Gb/sec interface and sustained 119.84 to 199.78 MB/sec throughput.

http://www.seagate.com/docs/pdf/data...etah_15k_5.pdf
Seagate introduces 15K rpm 2.5" hard drive | TG Daily

Oh how I miss SCSI.

It isn't SCSI giving you that kind of performance, it's the extra 7800 RPMs.

olePigeon · Mar 1, 2007, 06:11 PM

Originally Posted by mduell

It isn't SCSI giving you that kind of performance, it's the extra 7800 RPMs.

It's also SCSI with a much faster interface and sustained throughput than ATA (at the same RPMs)

mduell · Mar 1, 2007, 07:53 PM

Originally Posted by olePigeon

It's also SCSI with a much faster interface and sustained throughput than ATA (at the same RPMs)

SATA is the interface for SAS. SCSI is just the command language.

olePigeon · Mar 2, 2007, 02:26 PM

Originally Posted by mduell

SATA is the interface for SAS. SCSI is just the command language.

Not exactly. While they're both serial and don't have the same crosstalk problems as parallel interfaces have, SAS does have a different voltage and a slightly different connector. SAS was designed to be interoperable with SATA drives; you can attach either SAS or SATA drive to a SAS backplane. However, SAS will not work on an SATA backplane.

Asside from the physical connection being slightly different, the actual SATA interfaces start at 1.5 Gb/sec while SAS starts at 3 Gb/sec. You can even have dual SAS connections on a single SAS drive for higher bandwith.

SAS is faster than SATA even at the same RPMs, especially in RAID configurations with high throughput requirements.

Supposedly, SCSI drives are manufactured to higher standards than ATA drives, but that's debateable. There's an interesting study released that tested some 10,000 different HDDs. It found that SCSI drives were no more reliable than ATA drives when it came to hardware failure.