SCSI questions?

[Grant_H]

I know all about IDE and SATA and a little about RAID, but can someone explain to me about SCSI, it's advantages and so on.

[bazooka]

SCSI - Small Computer System Interface.

It is used in macs.

It is also used in raids.

Scsi is good for daisey-chaining drives together.

They have a longer mean time between failure.

Here is a good site.

http://www.dewassoc.com/kbase/hard_drives/scsi_vs_ide.htm

[Capmaster]

SCSI is also used in Xeon-based servers and workstations.

I have a Xeon WS at work that has a 15K RPM Ultra320 SCSI hard disk and that's the fastest thing I've ever stored data on. Holy crap, that thing is fast

The downside: hellishly expensive for the drive, and for the controller. And relatively small compared with the mondo-big SATA drives. But ....a Ferrari is smaller than a Buick, after all

But it's not unusually noisy, as many people have reported. Maybe because it's a Seagate - a typically quiet drive

[rallynavvie]

Also keep in mind one of the largest advantages to SCSI is that the controller is on the drive itself, thus all the crazy logic chips all over the undersides of them. This cuts down utilization of system resources by a lot when compared to a similar amount of SATA or PATA drives. The chaining is also a nice feature as each SCSI channel can handle up to 15 devices IIRC. The reason they cost so much is because of the generally much better quality of the drive components and build. This, along with certain platter sizes, allows them to attain the 15,000 RPM speeds and sub 3-second avg seek times. U320 is also capable of 320MB/s bandwidth. Considering SATA is only 150MB/s that's a big difference.

I haven't noticed the noise much either. You can really tell when you boot them up but otherwise my Seagate Cheetah 15K.3s have been pretty quiet. I just put them in as my boot array on my HTPC/file server and I thought having the OS on them would make them really noisy but I don't notice much of a difference in them over just PATA drives. Of course that PC has enough fans to levitate so I think that has something to do with drowning out the hard drive noise. They're really only noisy when accessing anyway. Older ones are a little noiser, but newer ones with FDBs are very quiet.

Are you looking into SCSI? I can recommend some items to cruise eBay for. That's where I get some of my equipment, the rest is from businesses closing and selling stuff off. Used SCSI is just as good since it's warrantied for so long you can RMA it without receipts years after you bought it used (at least you can with Seagate drives).

[Grant_H]

I'm putting together a compleatly new system AMD64, I plan on OCing it a bit. I havn't put together a system in a couple of years and have been doing quite a bit of reading up on the newer types of hardware out there. So If SCSI is faster and over all better, I might use it. I need some kind of SCSI controller I think, Is it a PCI card?

[glockjs]

I'm putting together a compleatly new system AMD64, I plan on OCing it a bit. I havn't put together a system in a couple of years and have been doing quite a bit of reading up on the newer types of hardware out there. So If SCSI is faster and over all better, I might use it. I need some kind of SCSI controller I think, Is it a PCI card?

yup, pci card. get ready to spend some $$$ though. go with Adaptec. www.newegg.com would be a good place to look.

[enstg8er]

i use a small 10k drive for booting. this can be cheap and still get very good performance. top speeds of 15k drives and 64bit pci adapters get expensive quick. out of my league anyway. also a factor-

This also might be a good place to note that SCSI is a true multitasking interface, while IDE/ATA is a single-tasking interface. Each device on an IDE channel needs total control of the bus in order to 'talk' (transfer data). SCSI, on the other hand, can have multiple 'conversations' occurring concurrently.

http://scsi.radified.com/
lengthy and somewhat outdated but still very informative. i recommend taking the time to read it.
i second the ebay route. cheapest way i've found.

[rallynavvie]

First thing to learn about SCSI: don't call it a SCSI controller. It is a "host adapter" since the "controllers" are on the drives themselves. Old SCSI crones will hate you for calling it a "controller card" or similar

I guarantee the SCSI hardware will be the most expensive part of your system (unless you're using AMD FX chips). I wouldn't go less than U160 (160 MB/s bandwidth) hardware since it was a big jump in tech from SCSI2 or UltraWide. I'd recommend U320, and forget fibre channel because it's quite a bit more for it and really only necessary in server environments. There are two big SCSI drive manufacturers: Seagate and IBM/Hitachi. IBM made some stinker drives but their latest Ultrastars are great. Seagate tech has pretty much been the standard for SCSI for a while though so you can't go wrong with them. Unless you need server-like responses (we're talking full duplex GbE access) you won't need to stripe your SCSI drives, just use them singly. 18 or 36GB drives are the most economical, but having a couple 10k 73 or 147 GB drives for storage would be fun. Make your best drive your boot drive. Best would be a 15k U320 36GB disk. To leaven your system maybe use large SATA or IDE for long-term storage and backup.

For a host adapter look at Adaptec and LSI. I like Adaptec's hardware. I've got a 29160 in my primary for U160 SCSI scratch disks and the other has my prized 2120S U320 adapter. Best bet is to find a 29160 or 39320 on eBay depending on if you want U320 support. Also look for your Seagate SCSI drives on eBay. A lot of them have a lot left on their warranty too.

[Grant_H]

Thanx for all the info, Now I have to deceide if I want to spend the extra $$$. I think I will go with an SCSI drive for my boot drive and use a couple SATA drives for storage, and mabey upgrade to more SCSI drives later down the road.

[stiltman]

I have never had a problem with my AHA-2940AU.
It's rather old, like 4 years, but works great

[Capmaster]

The reason they cost so much is because of the generally much better quality of the drive components and build. This, along with certain platter sizes, allows them to attain the 15,000 RPM speeds and sub 3-second avg seek times

Dayyymmmm rally I've gotta turn you on to a better HD supplier

Just pulling your chain, big guy I know you meant "sub-3 millisecond"

They are quite a bit better, but also quite a bit more money. One of the main reasons why I have one at work and not at home My standards are lower when I'm payin' the tab

[rallynavvie]

Nah, I can use a stopwatch to time my access times on my 15k drives

FWIW: Seagate 15k.3s are the bizzomb for boot drives. I can't complain about my 10k SATA drive though. That's a lot quieter and still pretty fast for a boot drive.

[enstg8er]

anyone know if/when the new pci format is going to knock down the price of the 64 bit hardware?

[rallynavvie]

Likely not for a while because of how much existing server hardware is based on old tech. We still run a dual Tualatin P3 IBM server at work which I'm surprised doesn't have ISA slots

I think blade servers and rack equipment is still using 64-bit PCI to save on space.

[enstg8er]

do you know of any 320 cards not using 64 bit?

[rallynavvie]

You mean for 32-bit PCI slots? I can't think of any U320 hardware that is native 32-bit, but I think there may be some that work in 32-bit slots and are just limited down to that slot's bandwidth. At least I know the entry-level LSI U320 HBA works in 32-bit slots. Is that what you were looking for?

[enstg8er]

i'll have to look into it. i'm always looking for cheap speed (who isn't?), i'm just not smart enough to know what to look for. thanks for the tip...