2 identical model Sata disks....different sizes

[ikonia]

hi.

I've bought 2 identical model Sata disks from overclockers.

they are both supposed to be 80gig.

When I plug them in the bios shows them as identical model numbers (great)

However it also shows them as different sizes.

fdisk shows them as this

Disk /dev/sda: 80.0 GB, 80032038912 bytes
255 heads, 63 sectors/track, 9730 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes


Disk /dev/sdb: 81.9 GB, 81964302336 bytes
255 heads, 63 sectors/track, 9964 cylinders
Units = cylinders of 16065 * 512 = 8225280 bytes


now heres the question.

Why do two disks, bought from the same respectable distributor with the same model number have different configurations like this.

Any thoughts ?

the reason I ask is this is causing me no end of pain in a mirror siutaion.

[Stephen B]

If your sizes are reported by the raid controller, I'll take a wild stab and say one drive is holding specific raid data on it, in a protected location in case of errors

[ikonia]

the raid controller is disabled.

This is reported at the bios level even with 2 blank disks

[Stephen B]

ah well, dunno, but thnx for helping me reach 50 posts

[ikonia]

ha ha, at least someone got some help.

The current configuration on these disks is a base OS install on them - and a software mirror on them.

The disk size was reported the same on these disks fresh out of the box.

the most interesting thing for me is, that they both show the same ammount of bytes

[Hans Voralberg]

Manufacturer variation may be?? The only explanation i can come up with. But if they have the same amount of bytes how can they differ in term of Gigabytes ???

[ikonia]

this is the golden question, and they both have the same model number, normally when a change means a change in number also

[arthurleung]

HDD's density is getting higher and higher nowadays. There must be some "error" inside every harddrive, regardless of is it 5mb or 5GB or error.

My two maxtor 160Gs have different size (One show 160G and one show 164G)

Those hdds started with may be 170G in size. The part that have error is marked not to be used, effectively reduce the usable area. Some hdds may be made better and have 164G, and some may only have 160G. Companies don't throw away things, they mark it down and sell. AMD sold XPs with some broken cache cheaply, A64 with some broken cache cheaply. Same for hdd manufacturers. If there are 40G of bad sector in a 160G HDD, they can mark it down to 120G and sell.

It still have 120G of actual storage, give or take.

Some manufacturer may have made all hdds between 162~166GB but cap it down to 160GB exectly. They may look like the same but some useful area is hidden.

Do you want the extra 1.9GB of not? When it is spec-ed at 80.0GB?

[Stephen B]

you tried swapping the data cables over to see if the problem stays with a particular drive ?

[ikonia]

not swapped the data cables, not sure how a cable would miss read a drive but worth a go.

not bothered about the exta 1.9 gig, however it is causing my drive mirroring proble,s