Does anyone know if the IBM Deskstar 120G is an ATA/66 of an ATA/100, and how can you tell anyway?
You need the model number of the drive. Unfortunately, Deskstar is not a model number it is an entire line of drives analogous to Chevrolet.
This table <http://www.hgst.com/hdd/support/table.htm> lists all (I think) of the IBM hard drives by model number and model family. E.g. the Deskstar 75GXP family includes six different drives wtih the model numbers DTLA-3070xx where the 'xx' is a two digit number indicating drive capacity.
There are three or four drives on that table with a 120 GB capacity and they are all ATA-100.
Going back to a discussion from a few weeks ago regarding drive speeds...
I mentioned in that earlier thread that at least one of the drive manufacturers lists real drive performance in their technical data. That manufacturer appears to have been IBM. If you use the links on the table above to view information on various drives, you'll find links for "datasheet" and/or "product summary" for each drive with a couple of clicks.
These documents will list a "media transfer rate" an "interface transfer rate" and a "sustained data rate". The latter may be listed as "minimum sustained data rate". IBM changed their nomenclature over the years, so early drives may have somewhat different listings.
Anyway, when trying to assess the performance that you will actually get from a drive, the "sustained data rate" or "minimum sustained data rate" is the number you should look at. It is very different from the "interface transfer rate".
Here are some examples of the sustained data rate followed by the interface data rate (all from the Ultrastar line, except the first and last):
0664 M1H 5.22 MB/s 10 MB/s 2ES DCAS-34330 5 - 8 MB/s 20 MB/s 2XP DCHS-34550 10.3 - 15.4 MB/s (media rate) 10 MB/s 9ES DDRS-34560 8.3 - 13.3 MB/s 20 MB/s 18ES DNES-309170 12.7 - 20.2 MB/s 20 MB/s Deskstar 75GXP DTLA-307045 37.7 MB/s 100 MB/s
The first five drives are all older SCSI drives. The last drive is a more recent (three years old) ATA-100 drive. I wrote above that you should look for "sustained data rate", but you can also use the "media transfer rate" but you'll need to divide by 8 usually (it's listed in megabits/second instead of megabytes/second) and real performance (sustained rate) is a bit slower than media rate because of overhead.
Notice the progression in speed? I've listed them pretty much in order of release date. They keep getting faster.
Notice that the interface speed bears almost no relationship to the sustained data rate? Yet, interface speed is what most people list for a drive speed.
Interface speed is the speed of the electronic interface between the drive and the computer (or SCSI card). Sustained data rate is how fast the hard drive is actually capable of delivering data to that electronic interface.
It's like the difference between shipping capacity and how much you can actually ship. Suppose I run a fruit cake company and own some trucks. It doesn't matter if the trucks can deliver 4000 fruit cakes a day, if I can only bake 250 fruit cakes per day.
Another thing to note is that most of those drive listed are 7200 RPM drives (two are 5400). Yet look at the difference in speed. Drive rotation speed doesn't really tell you much about actual drive performance except when comparing drives from the same model year. A 5400 RPM drive may be faster than 7200 RPM drive if the 5400 RPM drive was designed two years later than the 7200 RPM drive.
However, rotation speed can tell you something about when a drive was released. If a drive is 10,000 RPM, you know it came out within the last five (?) years. Faster spinning drives are even more recent.
However, that's still not *that* useful, as you should usually avoid at least the first year's drives for a particular rotation speed. For example, the first Cheetahs (Seagate's first 10,000 RPM line) were very very hot and rather loud. They were amazing in their day, but there's no reason to put up with that now.
Or the example in my original post a few weeks ago--the Seagate Barracuda. The early Barracudas were the ST32550 and ST15150. They spin at 7200 RPM, among the very first mass market drives to do so. They deliver 6 MB/s and 4.5 MB/s sustained data rates. Would you rather have an ST32550 or an IBM 75 GXP? They both spin at 7200 RPM, but one delivers five times the real world data rate as the other. And the early Barracudas were hot and loud...
Let's see, any other nitpicking little details about drive performance...oh yes. Most of those drives I listed above are/were available with two or three different SCSI interfaces (obviously not the 75GXP). Each SCSI interface yielded a different interface transfer rate (e.g. 20 MB/s for Ultra SCSI, 40 MB/s for UltraWide SCSI) but the same model drive has exactly the same "sustained data rate" regardless of which interface was glued onto it. So two drives with the same drive mechanism but different interfaces, means they have the same sustained data rate, regardless of the interface.
The main exception to this is the case where the drive performance (sustained rate) exceeds the interface rate for one interface and not for a different interface. I don't think I've seen that in the real world, but we'll consider an example anyway.
The 2XP appears to be an example, but that's because I could only list the media rate and not the lower, more realistic sustained rate for that drive. But let's pretend that the media rate is the sustained rate for that drive.
The 2XP was available with Fast SCSI, Fast & Wide SCSI or UltraWide SCSI interfaces. The interface transfer rates for them are 10 MB/s, 20 MB/s and 40 MB/s respectively.
With a sustained rate of 10.3 - 15.4 MB/s the 2XP is going to exceed the capabilities of the Fast SCSI interface. With the Fast (10 MB/s) SCSI interface, the 2XP will only deliver 10 MB/s. With the Fast & Wide (20 MB/s) interface, the 2XP will deliver 10.3 - 15.4 MB/s and with the UltraWide (40 MB/s) SCSI interface the 2XP will deliver 10.3 - 15.4 MB/s.
I went through the somewhat unrealistic example above because you can generate a similar situation on your Mac. If you take an Ultra (20 MB/s) SCSI interfaced drive and install it on the Fast (10 MB/s) internal SCSI bus of an S900, the best you'll see out of it is 10 MB/s. That's true even if the drive is an 18ES with a sustained data rate of 12 - 20 MB/s. If you install it on the unenhanced (5 MB/s) internal/external bus or on a C500 or C600, you'll get 5 MB/s.
So, if you wish to maximize performance, look for a drive with the best sustained data rate that you can find, but there's no point in getting a drive with a faster sustained data rate than the SCSI bus on your computer (or on your PCI card). The problem with this advice, is that it can be so darned hard to discover the sustained data rate for a drive.
Everyone publishes the nearly useless interface transfer rate (SCSI speed). As far as I know, only IBM actually lists the real world sustained data rate. Maybe some other manufacturers do and I missed it. But in any case, you must look up the technical documentation for each drive model to get the information.
Going back to William's question--it doesn't really matter if your drive is ATA-66 or ATA-100 or even ATA-133 because no hard drive is delivering sustained rates of even 66 MB/s yet. So in all of those cases, your interface transfer rate is comfortably above your drive's sustained data rate.
Finally, one last thing. The sustained data rate and media transfer rates show such a large range for each drive because the rates are different depending on whether the drive is accessing tracks near the center of the platter or near the edge of the platter. The drive spins at a constant speed, so tracks near the edge are moving faster and deliver data faster than tracks near the center of the platter.
This tends to mean that the first stuff you put on a drive will be accessed at higher speed than stuff that you store on the drive later. Hard drives are written from the outer edge inward (at least they were last time I checked).
Jeff Walther
-- SuperMacs is sponsored by <http://lowendmac.com/> and...
Small Dog Electronics http://www.smalldog.com | Refurbished Drives | Service & Replacement Parts [EMAIL PROTECTED] | & CDRWs on Sale! |
Support Low End Mac <http://lowendmac.com/lists/support.html>
SuperMacs list info: <http://lowendmac.com/supermacs/list.shtml> --> AOL users, remove "mailto:"; Send list messages to: <mailto:[EMAIL PROTECTED]> To unsubscribe, email: <mailto:[EMAIL PROTECTED]> For digest mode, email: <mailto:[EMAIL PROTECTED]> Subscription questions: <mailto:[EMAIL PROTECTED]> Archive: <http://www.mail-archive.com/supermacs%40mail.maclaunch.com/>
---------------------------------------------------------------
The Think Different Store
http://www.ThinkDifferentStore.com ---------------------------------------------------------------
