Path: utzoo!attcan!uunet!samsung!usc!apple!sun-barr!newstop!sun!stpeter.Eng.Sun.COM!cmcmanis From: cmcmanis@stpeter.Eng.Sun.COM (Chuck McManis) Newsgroups: comp.sys.amiga Subject: Re: Re: Erasable optical drive Message-ID: <137412@sun.Eng.Sun.COM> Date: 16 Jun 90 00:59:17 GMT References: <4714.AA4714@sosaria> <30810@cup.portal.com> Sender: news@sun.Eng.Sun.COM Distribution: na Organization: Sun Microsystems, Mt. View, Ca. Lines: 39 In article <30810@cup.portal.com> (Dana B Bourgeois) writes: >... I don't think the Amiga file system can support >this now. Am I mistaken? If the files are limited to the device size, >are there plans to fix this in future OS releases? A little bit. The Amiga Disk I/O subsystem is structured as a series of layers, the top most is the file system handler which sends and receives DOS packets to applications, the next level down is the device driver which communicates with it's clients via exec messages. The current filesystem handler has a one to one correspondence between the device it is controlling and filesystem it places there. However, there is no reason one couldn't write a filesystem handler that uses several devices to actually store the data, or several instances of media from one device to store the data. Consider a "virtual" hard disk which was actually stored on 20 floppy disks. The handler would have to periodically have to put up a requester asking for a different disk but the concept is possible. Applications would be able to use this funky disk because I they do is talk the handler packet protocol which is the "same" for all file system handlers. Additionally, the handler could be left alone and some smarts could be placed into a scsi device driver that would create a virtual disk out of 2 or more physical disks. This is how some people build fault tolerant disk drives for PC's and such, generally they take it a step further and have a SCSI interface with some firmware which exports the SCSI protocol etc etc. Anyway, the answer is that the OS supports the concept, the handlers and device drivers that are currently shipped do not. However, there are legitimate ways to replace the shipped handlers and device drivers to "bolt" on the capability in an OS friendly way. -- --Chuck McManis Sun Microsystems uucp: {anywhere}!sun!cmcmanis BIX: Internet: cmcmanis@Eng.Sun.COM These opinions are my own and no one elses, but you knew that didn't you. "I tell you this parrot is bleeding deceased!"