slow or fast HDD format?

[wideangle]

Got myself a new 1TB HDD to move my years of photographs over too, but was wondering if I should do a fast or slow format of the new drive, taking into account it would take around 5 hours to format it slowly. If there is an advantage of doing a slow one then I will do it.

[joffa]

There's no difference mate, just do the quick one. It'll work fine.

[bigbikes]

I have always only ever done a fast format on my new h/drives and never had a problem. I have no idea what advantage doing a slow format has, but I'm sure there would be a reason for it.

[joffa]

All it does is erase all the data on your disk and replaces it with 0's. Whereas a quick format just writes a new File Allocation Table etc and doesn't do anything to the rest of the disk.

[wideangle]

All it does is erase all the data on your disk and replaces it with 0's. Whereas a quick format just writes a new File Allocation Table etc and doesn't do anything to the rest of the disk.

So that would mean you would probably be better off doing a slow format on a used HDD to totally clean the slate, whereas with a new drive that is brand spanking new then the quick format it the go.....

[joffa]

Well not really, it really doesn't make much difference I don't think. Unless you have something on there that you don't want to be recoverable by anyone.

If that's the case do a full format, but otherwise both give the same end result. You just save yourself a few hours of waiting.

[Kym]

Fast! It was done in test/burn in in the factory. Plus slow does not do any error checking.

[pgbphotographytas]

if the drive is brand new just do a fast and start using it :th3:

[Tannin]

Slow format is good where you have any reason to suspect the drive. Otherwise quick.

[Tannin]

Pretty close, Rich. Sheesh, it's been a long time since I used to know this stuff backwards. I don't generally need to know too much of this these days. Memory: use it or lose it!

Let's see how much of it comes back to me.

As I recall, it's not actually the slow format that maps out the bad sectors. It used to be, but that was a long, long time ago. Back in the days of MFM drives (typically 20MB or 40MB. Yes, MB, not GB.

There were (and in fact still are, but you wouldn't know it these days, for reasons that will become clear shortly) three levels of format:

1: Low-level format. This you used to have to do by jumping into the hard disc controller card BIOS from DEBUG. You had to know the address of the BIOS entry point, and it was different with every different brand of controller card. You had to specify everything: physical tracks, heads and sectors, interleave, the lot. Then you started the format. It typically took a long time - hours, or overnight sometimes, and you had to guess what the best interleave was going to be for any given combination of controller card and hard drive. Set it too low and you lost performance - quite noticably so. But set it one notch too high, and you lost a heap of performance, the whole system became a complete slug. So you always tried to take it as high as you could, but not go that one step too far. Oh, and you just had to know the CHS (cylinder, head, and sector) numbers for any particular drive model. It wasn't generally printed on them, and the Internet was just a dream back them. Sometimes you had to guess.

With many controllers (perhaps most - hard to remember now, we are talking late 1980s and very early '90s) you could also hand-enter a series of known bad sector addresses. Drives used to come with a bad sector list printed on the label. These were the sectors that tested bad at the factory, but others would typically develop over time.

There were also amazingly useful third-party programs like Spinrite that would automate the calculation of interleave and intensively test the drive to map bad sectors. When that came along - wow! How much easier it all became!

Anyway, that was low-level formating. Later on, in 286 days, you didn't need DEBUG, you could do it direct from your mainboard BIOS.

Then you (2) partitioned (as you still do today) and (3) high-level formatted. If I remember correctly, there was a second layer of bad sector mapping at this level. But maybe I'm dreaming - it was a very long time ago and my memory is shocking.

Everything changed with the advent of the embedded controller. IDE (or ATA - same thing) is the best known one of these, but there were various forms of SCSI, and the mysterious and rather snazzy EDSI - two-cable drives that looked like MFM or RLL units, but weren't, they were pretty much always expensive, high capacity, high-performance units. (Often as big as 80MB!)

The embedded controller pretty much took low-level formatting away from the user or technician and performed it at the factory. (Not always, but mostly.) Nevertheless, the basic idea remained the same: the LLF process marked bad sectors and set them aside not to be used. There was (and still is) a facility in the drive firmware to add extra sectors to the bad sector map if extras developed.

And this, I suppose, brings my random ramble down loss-of-memory lane up to the present day, where the difference between a quick format and a slow format is (as ever) that the quick one only wipes the indexes, where the slow one overwrites every sector. And this, at last, brings me to the point I was going to start with before I got sidetracked - the bad sector mapping during a slow format (if I remember correctly, which is no better than an even money bet) is actually not because of the format. It simply happens because both the drive and the operating software are always on the lookout for bad sectors, which they detect by attempting to read from or write to the drive and failing. So, in theory, you could achieve the same effect by writing a whole lot of data to the drive. Unless I've forgotten something, which is almost certain.

Clear as mud?

[Roof]

1: Low-level format. This you used to have to do by jumping into the hard disc controller card BIOS from DEBUG. You had to know the address of the BIOS entry point, and it was different with every different brand of controller card.

I've always been told that a low level format makes the drive slower, it has been used by virus creators in the past...............but that is what other people were telling me.


When i bought my TB i don't think i formatted it............just used it straight away......but if i did a format i used the quick version.............i always do.........goes faster........

[oldfart]

For what it's worth I fix PC's for a living,

the rule of thumb around here is quick format on new drive, full format on used drive.

(and Spinrite on any drive suspected of problems)

[MarkW]

One of the issues using a Mac is all the damned HDDs are formated for PC so I have to reformat back to a decent Mac state.

I can buy a Mac preformated HDD but you pay a whack more just for some somebody else to do the format for you. At least it doesn't take days to do.