Our notebook supplier says they cannot provide the exact same model of disk in all units of a fairly large order.
Assuming that most data will be packed in the beginning of the drive (we use Ghost on the template development machine, which should be doing a defrag as it makes its image), how can there be any data loss if there is a small difference in size between two models of drive?
The alternate paranoid approach is to make an image file for every model of drive involved. If there is no real need to do that, we'd like to avoid the extra efforts involved in making a new image file each time a new model of drive is encountered.
--Donald Teed
On Wed, 26 May 2004, Donald Teed wrote:
Assuming that most data will be packed in the beginning of the drive (we use Ghost on the template development machine, which should be doing a defrag as it makes its image), how can there be any data loss if there is a small difference in size between two models of drive?
Even if you do not have data in your last few blocks initially, your file system might still try to write some blocks there at some later point in time. This does not necessarily only happen when the disk is full. It depends on the algorithms of your file system and on the usage patterns.
The alternate paranoid approach is to make an image file for every model of drive involved. If there is no real need to do that, we'd like to avoid the extra efforts involved in making a new image file each time a new model of drive is encountered.
You could partition your drives in such a way that you do not allocate more blocks than are available on your smallest drive. Leave all the superfluous blocks unallocated, i.e. unpartitioned.
That way you might still get errors when cloning the full disk (that might depend on your cloning tool), but the file systems on your disks are nevertheless fully cloned.
- Felix
--- Felix Rauch | Email: rauch@inf.ethz.ch Institute for Computer Systems | Homepage: http://www.cs.inf.ethz.ch/~rauch/ ETH Zentrum / RZ H16 | Phone: ++41 1 632 7489 CH - 8092 Zuerich / Switzerland | Fax: ++41 1 632 1307
Thanks for that reply, Felix.
It looks like our best solution is to try to learn the drive models or cyl/sect/head counts of the various drives we may be seeing, and ideally create a master image on the smallest one. If we can't get a hold of the smallest one in advance, we'll just create partition sizes as if we were working on the smallest geometry and then image that and live with an error from udpcast (which would be something like "no space left on device"?).
--Donald Teed
On Wed, 26 May 2004, Felix Rauch wrote:
On Wed, 26 May 2004, Donald Teed wrote:
Assuming that most data will be packed in the beginning of the drive (we use Ghost on the template development machine, which should be doing a defrag as it makes its image), how can there be any data loss if there is a small difference in size between two models of drive?
Even if you do not have data in your last few blocks initially, your file system might still try to write some blocks there at some later point in time. This does not necessarily only happen when the disk is full. It depends on the algorithms of your file system and on the usage patterns.
The alternate paranoid approach is to make an image file for every model of drive involved. If there is no real need to do that, we'd like to avoid the extra efforts involved in making a new image file each time a new model of drive is encountered.
You could partition your drives in such a way that you do not allocate more blocks than are available on your smallest drive. Leave all the superfluous blocks unallocated, i.e. unpartitioned.
That way you might still get errors when cloning the full disk (that might depend on your cloning tool), but the file systems on your disks are nevertheless fully cloned.
- Felix
Felix Rauch | Email: rauch@inf.ethz.ch Institute for Computer Systems | Homepage: http://www.cs.inf.ethz.ch/~rauch/ ETH Zentrum / RZ H16 | Phone: ++41 1 632 7489 CH - 8092 Zuerich / Switzerland | Fax: ++41 1 632 1307
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Donald Teed -
Felix Rauch