Is SCSI worth it?

[-Acid-]

I've never used SCSI in any Amiga before but I do have the SCSI module for my CS2 060. I would like to know if it is it worth buying SCSI hard drives to replace my IDE ones? What sort of performance increases would I be looking at? the only thing i can compare it to now is vs WinUAE and writing to disk in UAE is blistering compared to the Amiga's on board IDE, would the difference be anything on that scale?

Also with SCSI there are many types of drives, are they all compatible with the Amiga? Is the Amiga limited to Parallel SCSI drives like SCSI 1/2/3 and Ultra 2/3 etc or can it use Serial Attached SCSI drives too? there is so many options here I am unsure of what to look for. Would something like this be suitable for the Amiga?

I've also got a Buddha Flash (out of action right now but i'm looking to get it fixed). I've never seen this working either, how much of a speed up would this give me when working properly with IDE drives?

What should I do?

[Locutus]

first thing, SAS is not going to work. Its a completely different storage system.

The Buddha Flash will not be much faster then the onboard IDE and will still drive up CPU load.

Which is where SCSI excels, disk I/O eats up a very large percentage of CPU time on a Amiga with IDE. SCSI on the other hand has DMA and eats up way less CPU time.

The end result is that the machine is much smoother in use, even with a slow SCSI disk (even something like a SCSI2SD).

Instead of using ancient SCSI drives you are best of checking for a SCSI<>IDE adapter, but they are pricy.

[iddqd]

Using SCSI drives, I assume you'd have to buy old used ones? I'd feel nervous about using such old harddrives for storage.

[rare_j]

SCSI as a technology found itself at use in servers for the latter part of its lifetime and as a result the drives were high performance, high rpm, high noise components. I personally would take a silent, lower performance ATA drive in a desktop any day. The noise of a 10000rpm server drive in a desktop quickly becomes unbearable. People used to use SCSI > IDE adapters but these are expensive.
The SCSI2SD looks like a bit of a winner though.

[Damion]

Yes - especially when handling large files the transfer rate (nearly 10 MB/s with your MK2) is considerably better, using much less CPU. (However, certain things like booting or opening drawers probably won't seem faster.) I think it's absolutely worth it, and wouldn't use a "bigbox" without SCSI. As for avoiding the annoyance of noise and flaky drives, check out the "aztecmonster" SCSI -> CF converters (ebay), they're of high quality, easy to use, and perform flawlessly.

I believe the Buddha is a PIO controller and won't provide much performance increase over motherboard IDE.

[Toni Wilen]

Unfortunately SCSI does not guarantee DMA capability, SCSI is not always any better than IDE in CPU usage or performance, sometimes it is worse.

That there are lots of PIO only (very slow, 4-5 IO accesses needed to transfer single byte..) and "fake"/"pseudo" DMA (Similar to IDE PIO performance, single IO access can transfer byte, word or long word depending on hardware data port width).

Only Commodore, GVP (Series II and later), Phase5 and Masoboshi made true DMA SCSI controllers. (Technically Supra also made one but it was crap, SupraDrive 2000 DMA, similar to A2090 which also had bad DMA design)

As was already mentioned, DMA SCSI controller + SCSI<>IDE converter is the best choice today but usually also quite expensive.

[Dagger]

I use a scsi hdd and a cdrom in my 2000 and also have a scsi compact flash bridge board and have found this is to be the setup I am happiest with so far. Using the cf makes it so much easier copying programs from my pc to the miggy hdd.

[Ami_GFX]

I've gone back to using IDE on my A4000D. I'm currently using an IDE to SD converter with a 4gb SD card. The scsi III on the Cyberstorm PPC was much faster but it was difficult finding a compatible drive that didn't put a large draw on the power supply. When the last one I found started to give signs of failure, I didn't want to install another 15-20 year old drive and went back to IDE. I was also having some overheating issues and took out anything I could that was generating a lot of heat and the SCSI III drive was getting pretty warm.

I have an IDE to SCSI III converter but it didn't work with cyberscsi. I'm getting ready to test it with an adapter in my A2500 with a GVP scsi card. Apart from price, the acard adapters are designed to be plugged into the back of a 5.25" optical drive and fitting one in my A4000 was awkward. There's more room in the A2000 so it shouldn't be such an issue.

[-Acid-]

The price of those bridge adapters is very high and i don't think i'm willing to pay for one until the prices are more realistic. Seems like I will stick to ide and sata drives on the ide port for normal use and UAE for moving large amounts of data at once. Looks like the scsi module is staying in storage for a while yet.

[Dagger]

amigakit are now doing scsi to sd which are not a bad price

[mech]

Locutus hit the nail on the head, scsi on the csMKII will be around 10MB/s max in synchronous mode and cpu overhead is not much.

there are tons of drives still out there. the 2.5" IBM Eserver drives are small(2.5",and although 10,000rpm they are pretty quiet and do not use alot of power.

for example:
http://www.ebay.com/itm/IBM-73GB-10K...AAAOSwpDdVcfUt

common sizes are 36GB,73GB and i think 146GB(but most were sas which won't work)
you will need a 80pin to 50 pin adapter with these.

[illy5603]

I can't think of any practical application where you need the benefits of SCSI on a modern Amiga. Compact Flash IDE is quiet, and plenty fast. The only time I actually considered a SCSI solution was when I was still running my BSS on a real A1200. During uploads the CPU would be pegged writing to the CF card and it would make the second node unusable. Very limited case scenario here, and at that it was cost prohibitive for me.

[RizThomas]

I have 3- A2000 where each one has a GVP SCSi card. The drives (most Quantum) whines so noisily that it realy turns me off from using them for longer time. Locally, SCSI drive are so hard to source and I don't want to resort to ebay for it.
My A4000 had both SCSI and IDE drives when I first got it. I ended up taking out the SCSI drive and replace the IDE with a CF drive. Now the A4000 is quiet except for the PSU fan.

For me, the SCSI-SD is an option only but not a necessity. These are my opinions anyway. Cheers

[dannyp1]

I wouldn't rule out Ebay for something like a harddrive. There are super deals for very low prices and you never have to leave your home.

[Ami_GFX]

Ebay is not a bad source of old drives if you shop around but the problem isn't the price, it is the age and previous use which makes them prone to failure after a relatively short time of use. IDE to CF, SD and Sata adapters are really cheap and reliable and don't stress the power supply or create significant amounts of heat inside the chassis. None of the SCSI solutions are cheap. If the Acard converter doesn't work out for the A2500, I will sell it and get one of the Micro SD to SCSI converters Amigakit sells. They aren't that fast but they still are as fast as the A4000's IDE ports and the speed I'm getting from the GVP SCSI controller is about the same. There are some inline SCSI to IDE and SATA adapters Acard makes but they are even more expensive and I'm not willing to spend that much money on something that might not work with Cyberscsi. After the last drive starting to fail, I've chosen reliability over speed.

There is another advantage to using IDE to digital media converters. Media replacement is cheap and easy to get if there is failed card. I've only had one such failure in over 10 years and that was with a camera that got lots of use.

[jaesonk]

SCSI always outperformed IDE on my Amigas. Of course, I'm just comparing SCSI to the vanilla IDE on the A1200 & A4000. I have SCSI on my Blizzard1260, CSPPC, DraCo, GVP4060, and probably something I'm forgetting.

I'm currently rebuilding an A4000 set-up. AmigaKit refurbed my RevB motherboard. It now has a GVP4060 fully populated with 128MB and is booting from a CF-IDE drive now. Boots in seconds to OS3.1.

I have a RaizinMonster CF-SCSI hotswap drive in the lower floppy bay. This will attach to the GVP4060. I intend to use it with a VLabMotion NLE to see how it performs. I can swap 4GB CF cards for individual projects.

I've used SCSI-SATA bridge adapters in the DraCo and a SCSI-IDE bridge. Adapters aren't inexpensive but the newer drives & media can be. Someone already mentioned the SCSI-SD adapter available through AmigaKit. It is one of the least expensive that you'll find.

Another way to boost your drive performance is with an alternative file system. I use PFS3 and have been very happy with it. There are a few alternatives to FFS available.

[alewis]

Sorry, have to comment here; SCSI is a vastly superior solution to IDE.

The bus can have up to 7 ('narrow' 8-bit SCSI) or 14 ('wide' 16-bit) devices per interface. IDE is limited to two devices per interface.
The bus can be considered to be 'multi-tasking' in that commands can be sent to different devices, and executed essentially in parallel (the target device will disconnect from the bus whilst it executes the command, freeing the bus for another device). IDE devices have to wait for a command to issued and complete before a further command can be issued.

Even better, one device on the SCSI bus could talk to another device directly, without the need for the host computer to control the operation, for example copying data from a hard disk to tape-drive, or CD-ROM to hard drive.

SCSI drives are quicker in operation as multiple commands to a given device can be queued on the device itself. IDE never had this, even SATA only supports an inferior form of command queuing.

Depending on the HBA (SCSI card), they often have a wider/faster bus bandwidth than IDE.

Most Amiga IDE cards use PIO (polled I/O) to transfer data. PIO is driven by the host CPU, thus the CPU is tied up for the duration of the operation. The upside is that a CPU upgrade [/i]may[/i] have the benefit of improving hard drive performance (strictly speaking, data transfer performance, as the drive itself operates at the same speed regardless)

Direct Memory Access (DMA) controllers do not involve the CPU other than initial start and end of the I/O operation (sending the command to load data, and where to put it in memory); the controller wrote the data directly to the memory starting at the specified location, and then signalled the end of the transfer to the OS/CPU.

Whilst many Amiga SCSI cards used PIO (or a variation), device drivers tended be written with multi-tasking in mind. IIRC the Supra WordSync controller was a non-DMA controller that did not tie up the OS and result in the hour-glass until the operation was complete.

SCSI came in numerous flavours. Forget SCSI-1

SCSI-2. This was the commonest interface standard on the Amiga, using an 8bit bus at 10MHz, over a 50-pin ribbon cable (or 25pin external cable, with all grounds tied to one pin... naughty). 10MB/sec transfer rate.

SCSI-2 also had 'Fast', 'Wide', and 'Fast-Wide' flavours. The most common, and as said, that used on the Amiga is "Fast-SCSI-II", or just "SCSI".

SCSI-3 This is where confusion can set in, as SCSI-3 has numerous sub-sets such as "ultra", "ultra-wide, "ultra-160" and so on. Generally, a SCSI-3 device/card uses a high-density 68pin interface. The bandwidth is anywhere between 40 and 320MB/sec. And yes, there are SCSI-3 adaptors for the Amiga; the Cyberstorm PPC came with one, as did the WarpEngine 040 card.


Reliability. SCSI drives tended to be MUCH more reliable than IDE! They were originally aimed at file-server operation, where 24/7 operation was the norm, and downtime due to drive failure was to be avoided at all costs. Given the exponential growth in storage requirements from the late 90;s (when 9GB SCSI drives were top end) through 18 and 36GB around 2002, to 146GB by 2005, most enterprise drives were not in service for as long as envisaged.

And given the multi-user environment they were operating in, SCSI drives are quicker in operation that IDE drives (aimed at the single user desktop). Again, command queuing and task-ordering helps, but SCSI drives tended to have lower access and latency times.

Noise. All comes down to the drive. A 15K RPM drive can be noisy, but I have some Cheetah 15Ks that are almost noiseless. I've had some that aren't, and 10K drives that fall inbetween.


So can you use SCSI in your Amiga? If you can find a good interface:

GVP on-board SCSI controllers such as those on the 50MHz 030 accelerator, G-Force 030 and 040 cards for the A/B2000 were DMA.
GVP Impact II iirc was DMA (SCSI-2 at 10MHz for 10MB/sec DMA transfer)

Any SCSI controller with a 68pin interface (Cyberstorm, WarpEngine)

Fastlane Z3, DKB4091 are DMA devices.

Is there any advantage over an IDE interface and CF card? No, and yes. The data transfer rate depends on the interface type and card speed, vs the speed of a given hard disk. Bear in mind that the 'xY' rating of card is "x times 150kbyte", the same as used for CD-ROM drives many moons ago. Thus a 133x card has a max transfer rate of 20MB/sec. No Fast-SCSI controller on the Amiga can match that (being limited to 10MB/sec by the bus)*1

But as always, there is more to life than headline 'speed', or data rate. If you are loading a large program or data file, the IDE solution will tie up the OS until it has loaded, whereas a SCSI controller will not (assuming DMA or well written driver).

And if you want to add extra devices, the SCSI route has this as standard - just keep adding devices and cables - and terminate the last device - until you reach 6 (or 14) devices. And remember, each device can talk to another without the Amiga being involved.

However, if you have an accelerator card with a SCSI-3 controller, its a different game. Go the SCSI route and add an U160 rated hard disk, preferably a 15K drive. Blistering performance, excellent seek times, and minimal latency, plus the expansion opportunities above.

The real eye-opener with SCSI vs IDE: Take the fastest IDE interface, and install a hard disk and CD-ROM as master and slave. Copy the CD-ROM contents to hard disk. I'd advise you to make a brew whilst its doing so, as even the multi-tasking Amiga will be slowed by this.

Now conduct the same, with a DMA SCSI card, hard drive and CD-ROM - even an 8x SCSI CDROM will complete the operation quicker than a 24x or 48x device in the IDE setup...

Comes down to horses for courses. Find a reputable ebay seller, and qood quality SCSI drives are cheap as chips. If you dont want to risk ebay, drop me a PM as I've several anyone can have for postage costs.

*in reality, a CF card is not going to achieve 20MB/sec anymore than a given drive on a given SCSI card is going to achieve 10MB/sec due to overheads.