“The reason you may experience problems with this setup is because it is not good practice to have two SCSI initiators on the same SCSI bus at the same time (an ‘initiator’ being a device with a CPU - such as a Mac/PC or sampler - communicating with a SCSI peripheral). Furthermore, many SCSI boards for Macs and PCs do not treat SCSI bus arbitration correctly (i.e. multiple initiators in a system is not handled correctly). As a result, SCSI bus crashes can occur when a hard disk is accessed by a sampler and a Mac/PC at the same time and depending on what the two devices were doing at the time, this SCSI bus crash can corrupt a hard disk easily. SCSI was never designed as a ‘networking’ system, just a means to connect a single initiator to SCSI peripherals such as disk drives, CD-ROMs, etc. (for example, you would not network PCs or Macs together using SCSI).
There are also other known problems when using a single disk shared by two SCSI initiators as shown above. These are not unique to sharing an S5/6000 with a Mac/PC but can occur on any SCSI system that has two initiators (for example, two Mac/PCs sharing the same SCSI drive). When a disk is ‘seen’ by a SCSI initiator, the disk’s directory is loaded into its RAM disk cache. The directory (also referred to as the FAT or File Allocation Table) is where all the information about the data stored on the disk is held. If the directory is damaged in even the slightest way, it is almost impossible to access the data on the disk.
Under normal circumstances (i.e. a single initiator hooked up to one or more drives), any changes you may make to data on that drive automatically update the directory in the initiator’s RAM so that it knows about the changes and can deal with the data correctly. However, in the case where there are two initiators sharing the same drive (as shown above), if changes are made to the disk by one initiator, the other initiator’s directory cache is not updated and so it doesn’t have the latest and current directory. And that’s where the problems start!
The kind of ‘real-world’ things that can go wrong are........
A. You delete some files on the disk using the sampler - they are deleted, the sampler’s disk cache is updated, the files don’t appear in the LOAD filelist and everything is fine. However, the Mac/PC’s disk cache has not been updated and so it doesn’t know anything about these changes - as far as it’s concerned, the files are still there and so it will still display the deleted or renamed items. This isn’t a problem in itself but if you try to do anything with
them, because they have been deleted, the system may get confused, the SCSI bus might crash and the system could lock up with a disk error and it’s possible that the Mac/PC could cause the disk directory to be corrupted causing irreparable disk failure. NOTE: The same could happen when renaming files.
B. You move some items from one folder to another on the Mac desktop or in Windows Explorer in an attempt to organise your sound library more logically. You will see the changes on the Mac/PC (of course). However....
The sampler knows nothing about the changes you made on your Mac/PC because its disk cache has not been updated so as far as it’s concerned, the files are still where they originally were. In the LOAD page, should you attempt to load these files, because they have been moved elsewhere and don’t actually exist in the folders shown on the sampler anymore, you
may get a disk error, possibly a SCSI crash and maybe even a directory corruption rendering the disk unusable.
C. If you edit a sample using a Mac/PC wave editor and save that sample back to the disk, the sampler will not automatically know these changes have even taken place. For example, if you chop a 1Mb sample in half on a Mac/PC wave editor, the Mac/PC’s disk cache is updated and it knows the new filesize. The sampler, on the other hand, has no idea that these changes have taken place - as far as it’s concerned, it’s still a 1Mb sample because
that’s the information it has in its disk cache. Should you try to load this sample into the sampler..... That’s right - the sampler is looking for a 1Mb file stored in a particular place on the drive, it doesn’t find it so there will be a disk error, probably a SCSI crash and possibly even damage to the disk.
D. The worst of all scenarios! You have the same sample loaded into your sampler AND your Mac/PC wave editor (maybe intentionally or accidentally). You save it on the sampler and, at the same time you save it on the Mac/PC. You now have two initiators trying to write different data to the same point on the disk. You may as well throw the disk in the bin! It’s a potentially ugly situation! And these are just four situations where things can go wrong. Bring into the equation SCSI ID mismatches, incorrect termination, etc., and you have a disaster waiting to happen!
None of this is due to limitations in the S5/6000 or the Mac/PC but is due to the fact that SCSI was not really intended to be used in this way, as a means of networking devices (that’s why networks of computers normally use Ethernet or something similar like AppleTalk). You can now begin to see why sharing a disk between a Mac/PC and an S5/6000 is not recommended - it’s possible but there are too many risks associated with it.
There is nothing stopping you sharing a drive with your sampler and your Mac/PC in this way. With care, you may be lucky and have no problems. However., there is a huge potential risk of irreparable data corruption. As such.... Should you choose to share a disk drive between your sampler and your Mac/PC via a direct SCSI connection as described on the previous pages, please be aware that you do so at your own risk and AKAI professional M.I. Corp. cannot be held liable for any problems you may have on your PC/Mac and/or S5000/6000 or for any damage to equipment or loss of data that may result if an S5/6000 is connected directly to a Mac/PC.”
