Hi Eric, I expect that in the next few years we'll see very large hard drives and they will continue to support 512 byte sector sizes - that is what the system manufacturers demand. The actual sector size of the drive might be 4KB but the drive will allow the host to choose a 512 byte or 4KB sector format and adjust accordingly. If 512 byte sectors are chosen and the drive is truly using 4KB it will do the proper read/modify/write sequence for writing random 512 byte blocks. For reads and sequential writes the performance impact will be negligible. Random writes present the biggest challenge - better drives will be able to minimize the performance impact. Most of us run with write caching enabled which also helps the performance problem that random writes cause.
From an operating system point of view things are more complicated. The classic partitoning scheme doesn't work well on giant drives. You are better versed in the newer partition table schemes than I am. We might just have to live within the limits of a 2TB device if we don't want to fix the problem. I think I can live in 2TB for my DOS systems ... In the early days of DOS device drivers often had to deal with sector sizes that were not 512 bytes. I have an Iomega Bernoulli Box A220 (2 8" cartridges holding 20MB each) that uses 256 byte sectors, and the device driver is responsible for dealing with that. I think even the later Adaptec ASPI drivers know how to work with SCSI devices that report 256 byte sectors. If we ever have to deal with this issue in the kernel I would be inclined to continue to use a 512 byte sector size within the OS and hide any differences at the lowest levels. This might not be as efficient as supporting different sector sizes natively but that probably becomes too complicated and error-prone. There is a lot of code that assumes 512 byte sector sizes and it is not worth disturbing it. I'm going to get flamed for this but I'm not too worried about the performance hit that translation layers cause. FreeDOS is *insanely* mismatched for modern hardware, and there is plenty of performance overhead available to dip into. Anybody who really needs the speed should step up to a more modern operating system. We're not making use of the hardware we have already and we're probably a decade or two late in trying to keep up with advances in hardware. Mike ------------------------------------------------------------------------------ RSA(R) Conference 2012 Mar 27 - Feb 2 Save $400 by Jan. 27 Register now! http://p.sf.net/sfu/rsa-sfdev2dev2 _______________________________________________ Freedos-user mailing list Freedos-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/freedos-user
