Lost Clusters versus Lost Sectors

[High_Jumbllama]

Just bought a USB2.0/ESATA 1TB drive. It works fine. All was good at first. A day and a half later my primary started making noises. I ran a scan and during stage four it popped a message about bad clusters. The machine continued to have trouble after the scan so I shut down. The next day I bought a 500GB drive to replace my data drive so that it could replace my primary. The cloning d(250) -> NewD(500) and c(120) to NewC(250) worked flawlessly. Thank you Acronis. Curious about the condition of the drive and not wanting to toss it I added it back in as an extra drive and ran chkdsk on it. It did not list any bad sectors after a format.

I decided for now to use it to store Virtual machines and hard drives for Microsoft Virtual PC 2007. I have these backed up and use them infrequently anyway.

I got the message about bad clusters and do not show any bad sectors. Does this make any kind of sense? It's never going back in as an important drive. Is this just an example of the drive remapping itself independent of the OS?

[rylan]

From my understanding, a bad sector is an actual error/defect with the drive hardware in one small area. A bad cluster is a group of sectors, meaning that a larger area of the drive had a fault.
Different scan programs may use different terminology, which would obviously make things confusing.

[UtwigMU]

Afaik in the old days sector was a part of track, while a cluster was group of all sectors one above another on multiple platters. Since now hard disks report cyls, heads differently than they actually are, it's meaningless.

[spadnos]

Afaik in the old days sector was a part of track, while a cluster was group of all sectors one above another on multiple platters. Since now hard disks report cyls, heads differently than they actually are, it's meaningless.

Err - not quite
A sector is a unit of storage on the physical disk. I don't think you can read or write less than one sector at a time, but I'm not positive about that. A cluster is just a filesystem-level grouping of sectors, used to increase the maximum disk size for a given FAT size. (or inode or whatever - depends on the filesystem)

chkdsk looks at a formatted partition, so if it finds a bad sector, it has to mark the entire cluster as bad, and since the filesystem can't deal with anything smaller than a cluster, it reports bad clusters. Format operates on a raw partition, so it deals with sectors. Of course, if it finds any bad sectors, it will mark that entire cluster as bad in the FAT (or other control structures), and report bad sectors.

- Steve