I'm curious as to how you got 16 drives on one FW. The limit is 15 SCSI addresses. If you are using an array, you can have multiple LUNS on each SCSI address. I don't know if there is a configuration maximum but the FW interface has limited IO throughput. For performance reasons, I've limited the DISC per FW channel to no more than 80Gb. The configuration is based on the throughput required by the application, not the physical limitation although I'm sure there is one. The most we have configured on any channel is 140Gb using 20 x 7Gb LUNs on an XP256 array. This uses 5 LUNS on 4 SCSI addresses on the same channel. Eucaristo, Tom Genute Phone: (212) 437-1744 Pager: (888) 778-7121 -----Original Message----- From: Steve Dirickson [mailto:[log in to unmask]] Sent: Friday, February 18, 2000 9:13 PM To: [log in to unmask] Subject: Re: Number of Disk Drives > We have a 987/200 running MPE/iX 5.5 pp 7 with a few reactive > patches thrown > on for good measure. I am trying to find out how many disks I > can hang off > of one FW/SCSI. I am interested in throwing all the rules > about performance > and stability and the dip switches on the hardware out the door. I am > interested in just the path limitations. Currently 987 is not > being used at > night. I currently have the EMC BCV back up procedure in > place on our test > machine and would like to move it. We only have two slots > available on the > 987 and moving the back up would exceed the 15 limit by > almost double. We > also have a machine that currently has 16 drives on one > FW/SCSI and it works > fine so I know the limit of 15 can be exceeded, I just don't > know by how > much. If anyone has put more than 15 drives on one FW/SCSI I > would like to > know how many as this amount may be high enough to let me > know I can do what > I want. I also have HP looking into this for me. A 16-bit SCSI channel (a.k.a. "Wide" SCSI) supports 16 targets, one of which is the adapter. Each of the other 15 targets can be drives, scanners, other adapters, whatever, but there are only 15 targets available. Each target may contain up to 8 Logical Unit Numbers (LUNs). Relatively few devices use LUNs; I've seen them used in CD and tape changers. If none of the target devices on the bus use LUNs, the maximum number of devices on the bus (other than the adapter) is 15. If all targets use LUNs, 120 devices can be addressed. I've never seen a stand-alone disk drive that uses LUNs, though they may exist. Steve Dirickson WestWin Consulting [log in to unmask] (360) 598-6111