Adaptec has long been a leader in the area of SCSI cards, and despite the company's reign it does not sit still. Today, I am reviewing Adaptec's 39160 Dual Channel SCSI card, and though officially it is targeted at the server market, it will work just fine in your Linux-based desktop PC.The card
The 39160 is physically similar to the other products in Adaptec's line of 160MB/second SCSI cards. The obvious differences are the increased number of connectors from lower-priced models, and the capability to use the card at full speed in 64-bit PCI slots, allowing the 39160 to take full advantage of platforms that support the feature, only found on higher-end boards.
The 39160 has quite a few connections. Externally, there are two 68-pin SCSI connectors for LVD (low voltage differential, a technology that allows for lower power consumption and faster data transfer) drives, each connected to a separate bus. Internally, there are also two 68-pin LVD connectors, connected to two separate SCSI busses, as well as a 50-pin internal connector for connection to legacy Ultra SCSI devices, such as CD-ROMs, or even older hard disks, if need be.
All of these connectors can cause a problem getting the maximum performance from your card. The idea is to keep the fastest devices separate from any legacy devices, specifically keeping LVD (Ultra 160, Ultra2) off the same chain as Ultra and lower legacy devices. If you need to connect such devices, your best bet is to connect the legacy devices to channel A (which is the channel the 50-pin internal connector is assigned to) and LVD devices to channel B. If you have no 50-pin devices, then legacy devices can be connected to channel A or B, as long as the LVD devices are on the opposite channel of the slower devices. The reason this problem occurs is that the way SCSI manages device speed is by limiting the channel to the slowest device on it.
As I mentioned above, the four Ultra160 connectors are split between two separate, full-speed 160MB/second SCSI channels. This means there is a total of 320MB/second of bandwidth available on the card for the Ultra160 channels. The way to get the best possible performance is to split the load evenly between the two channels. Each channel is detected by the Linux Kernel's Adaptec Drive as a separate device, channels A and B, as shown below:
scsi0 : Adaptec AIC7XXX EISA/VLB/PCI SCSI HBA DRIVER, Rev 6.2.4
[Adaptec 3960D Ultra160 SCSI adapter]
aic7899: Ultra160 Wide Channel A, SCSI Id=7, 32/253 SCBs
scsi1 : Adaptec AIC7XXX EISA/VLB/PCI SCSI HBA DRIVER, Rev 6.2.4
[Adaptec 3960D Ultra160 SCSI adapter]
aic7899: Ultra160 Wide Channel B, SCSI Id=7, 32/253 SCBs
Adaptec likes to support the Open Source community, and is even known to use Open Source software in solutions for its customers, such as using FreeBSD in digital broadcasting solutions. As a result, Linux support for Adaptec devices is excellent, with company engineers personally overseeing the development of the Linux driver. The 39160 is no different, and is supported by default with the included aic7xxx driver in the kernel.
The documentation included with the 39160, as we have come to accept with much hardware, does not include instructions for using the device under Linux; however, your distribution (if you are running Mandrake or Red Hat) should pick the card up and configure it automatically, and if that is not the case, perhaps it is time to visit the Kernel-HOWTO. As for the rest of the documentation, which deals with the physical installation of the card and subsequent installation of internal and external devices, Adaptec does a good job of explaining how to get the most out of your card. This can be tricky with a card like the 39160, where you have five connectors and two channels to choose from. I would suggest reading the manuals; they are brief but well-written, and extremely useful.
The price of the 39160 may be its most interesting aspect when comparing it to "lower-end" SCSI cards, specifically the 29160N, which Adaptec lists as a card for "high performance PCs." There is only a $50 dollar difference, which pushes me to recommend the 36160 for those who can afford it -- it's like paying $50 for the performance of having a second SCSI card, essentially.
If you do not think you will need many different SCSI devices, then you may wish to look at lower-end devices such as the 19160, which will probably provide you with all the SCSI you need. Either way, with its well-tested Linux drivers and its excellent expandability, the 39160 is an easy card to recommend, and it even comes with a reasonable cost compared to other SCSI cards in its range, coming in at about $300 according to PriceWatch. If you are thinking of becoming a serious user of SCSI, you won't beat the 39160 with anything less than a RAID card.