SCSI vs. IDE Plz explain and discuss...Thanks

[mjolnir2k]

I keep seeing SCSI devices talked about. Can someone explain the difference vs. my IDE devices (HDD etc) and what the benefits / negatives of SCSI would be.


ps. I did a search, but didn't find a lot of info. Hoping the pro's here could shed more light on this.

Thanks in advance.

 

[Daovonnaex]

SCSI and IDE (technically the term ATA is more accurate) are two methods of transferring data to and from storage devices. SCSI has historically always offered more bandwidth than ATA. Furthermore, a normal SCSI bus can connect seven devices per channel, whereas a wide SCSI bus can connect fifteen (one of which is a controller). ATA can only connect two devices per channel. SCSI also spares the CPU from doing any calculations, whereas ATA offloads its calculations to the CPU. Due to the more advanced nature of SCSI, SCSI hard disks tend to be more advanced. The fastest ATA drives have spindle speeds of 7200 rpm and 2MB of cache (excepting the WD JB series, with 8MB of cache). The fastest SCSI drives have spindle speeds of 16000 rpm and 8MB or 16MB of cache. As for other storage devices, ATAPI (ATA for other storage devices) are usually faster, mainly because companies have ceased to release other storage devices for SCSI because it is less profitable. SCSI must also be terminated at the end of the devices, and each device requires a unique SCSI ID defined by a number. As for bandwidth comparison, the ATA standard with the highest bandwidth, ATA-133 or ATA-6 (I may be wrong on the number, uses UDMA 133 to achieve a maximum possible of 133 MB/sec transfer rate. The fastest available SCSI standard, SCSI-3 SPI4 (usually called Ultra 320), can transfer 320MB/sec. However, most drives still only support SCSI-3 SPI3 (usually called Ultra 160), can transfer 160MB/sec.

 

[Buzzman151]

Do a search in General Hardware on just "SCSI"... that will answer all your questions....

 

[Oyeve]

Pick up this months issue of Maximum PC. There is a good article discussing IDE vs SCSI. Although they are Pro IDE (cuz of cost and mass consumers wants) it contains a good bit of info. I myself am all scsi.

 

[mjolnir2k]

Thanks all, Great info as usual.

I will do more searches and check out the magazine article as well.

*Knowledge is a good thing!

 

[Mavrick007]

SCSI= efficient cause of less cpu load use.
more devices can connect(7+).
expensive.
faster.
meant for server market.

IDE= less efficient cause of higher cpu use.
limited devices can connect(2/port, usually 4/machine)
cheaper consumer alternative.
much slower.
meant for consumer market.

I would use SCSI if I could afford it, but it's just not cost effective for me. Devices and hard drives can be found much more affordable now in ide or usb. And if I need a new 40+Gig hd, all I do is lay down under $100 for an ide cheap storage solution, but if I wanted SCSI, I am sure to pay hundreds of $ for the same size albeit better speed.

 

[lozina]

One more thing you forgot to mention: SCSI is LOUD and HOT. I've owned or worked with many scsi's and they all share these annoying traits =\ Sometimes when my SCSI drive is reading files I get scared and look out my window expecting to see a jet crash into my house...

 

[dullard]

SCSI's main benefit is the quick access time. So if you open many small files, SCSI is dramatically faster.

However, most SCSI drives have about the same transfer rate as good quality ATA (also refered to as IDE) drives. That means when you read/write a large file, the speeds are about the same. Yes a couple of great SCSI drives exist, but the vast majority won't beat a quality ATA drive when working with a large file.

Now look at prices at typical prices at companies such as Dell, Gateway, or HP (none of these prices are street prices):
80 GB 7200 rpm ATA: ~$100,

72 GB total from two 36 GB 10K rpm SCSI: ~$700 (typical SCSI speed - fast for small files, same as ATA for large files),
72 GB total from two 36 GB 15K rpm SCSI: ~$1250 (fast SCSI speed - better than ATA for all file sizes),
If you wanted to put those drives in RAID add $500 to the SCSI prices (result about $1200 and $1750 respectively).

For the vast majority of people, going from $100 to $1250 just isn't worth it. Realistically, how often do you wait very long for your hard drive to finish? (When you boot the computer or load a program a large portion of the time required is CPU time - so don't think it is all HD time.) It takes a fraction of a second to read/write most files. So $1150 more to save a fraction of a second isn't worth it to most people. Yes you could connect 15 SCSI drives - but the vast majority of us don't have 15 drives (or we can just buy an IDE expansion card for $20 if we needed that many drives).

edit: I made it clear that the 72 GB was from two separate SCSI hard drives. Yes there are single drives that size, but they cost more. The prices I listed were not the lowest street prices, but the prices that people must pay to have them included in a prebuilt machine (that is the reason I listed Dell, Gateway and HP - check the workstations on those pages.)

 

[Oyeve]

<< However, most SCSI drives have about the same transfer rate as good quality ATA (also refered to as IDE) drives. >>



Yes, but try to access multiple IDE devices at the same time and it chokes. With SCSI all devices can run at the same pace at the same time, at least until the PCI bus starts choking.

 

[RSMemphis]

One more thing you forgot to mention: SCSI is LOUD and HOT.

They are getting much better now. Well, if you get a comparable drive to IDE, then it is just as loud and hot.
But even the new Seagate 15k's are not that loud - have you had a chance to check them out yet?

 

[Wolfsraider]

<< 72 GB SCSI: ~$1250 (fast SCSI speed >>

:Q

where is this selling please dude please

I wanna see too

just a link or a pic please lol

wouldn't two 36 gig hdd's be better/cheaper?

 

[Pariah]

"72 GB SCSI: ~$700 (normal SCSI speed - fast for small files, same as ATA for large files)
72 GB SCSI: ~$1250 (fast SCSI speed - better than ATA for all file sizes)
If you wanted to put those drives in RAID add $500 to the SCSI prices."

The fastest 73GB SCSI drive on the planet, the Maxtor Atlas 10K III sells for $719. The second fastest 73GB SCSI drive (and only other one on the market), the Seagate 73LP sells for $665. There is no normal speed 73GB drive, whatever that means. The only SCSI drive available that costs more than the 73GB Atlas is the 180GB Seagate Barracuda which sells for about $1450.

 

[Wolfsraider]

thanks for explaining

i thought you meant 73 gig hdd sorry

now i see

2x 36lp +raid controller got it

 

[dullard]

<< i thought you meant 73 gig hdd sorry >>


My fault, I chose the cheapest option to get as close to the 80 GB as I could. Thus you need two 36 GB SCSI drives. I did not make that clear enough.


<< just a link or a pic please lol >>


Dell - press continue to see the configurations. (80 GB ATA-100 is $70, two 10k 36 GB SCSI is $749 + $699 if you want RAID, two 15k 36 GB SCSI is $1249 + $699 if you want RAID).
Compaq. (80 GB ATA is $140, single 10k 73 GB SCSI is $1150, two 15k 36 GB SCSI is $1449, RAID is already included in base price so I cannot determine it).

 

[rockhard]

For me i have found that SCSI has better seeks and throughput, but what really clinches it for me is how you can have say 5 or 6 apps trying to access the HD at the same time, the SCSI setup ques the HD accesses and allows your rig to get on with something else.
The IDE setup trying to do this brings your rig to a crawl while the HD accesses are being processed. Only once theyre done can your rig be totally free to get on with its stuff.
If you heavily multitask with disk IO then SCSI is the only way to go IMO FWIW
Also SCSI HD's have a better warranty and ARE more reliable in general.
I personally would not even touch a IDE setup unless it was raid 1 as ive so much bad luck with IDE HD's crapping out on me under heay use

 

[Pariah]

"The prices I listed were not the lowest street prices, but the prices that people must pay to have them included in a prebuilt machine (that is the reason I listed Dell, Gateway and HP - check the workstations on those pages.)"

If you're going to give inflated OEM prices for SCSI, you have to do it with IDE as well to make it a fair comparison. An 80GB 7200RPM IDE drive from Dell does not cost $70. It costs an additional $70 to replace the default 40GB drive. If you want to add an 80GB drive on top of what is in the system, it costs $219. Also, if you're computer literate enough to know what SCSI is and the strengths and shortcomings of it, you're literate enought to install it yourself, and save about 1/3 of the cost Dell would charge you.

Those Compaq prices are absolutely ridiculous. No one spending their own money and having an ounce of common sense would pay those prices.

 

[dullard]

<< An 80GB 7200RPM IDE drive from Dell does not cost $70. It costs an additional $70 to replace the default 40GB drive. >>


Correct, however the SCSI prices also do not cost what I listed (It costs an additional $749 to replace the default 40GB drive). Thus the price difference stays the same. Think about it this way, lets keep the default 40GB drive and add the 80GB IDE or the SCSI drives. This way it still costs $1150 MORE to upgrade to SCSI.


<< Those Compaq prices are absolutely ridiculous. No one spending their own money and having an ounce of common sense would pay those prices. >>


Sadly, many people do pay them.

 

[Pariah]

"This way it still costs $1150 MORE to upgrade to SCSI."

Dell's prices are a joke too. That's still not a valid comparison as no one with half a brain would pay those prices. If you do, you deserved to get burned. Who would pay someone $400 to install 2 hard drives for them? Dell's site is messed up too, you can't get a 36GB 15K drive as a second drive unless you get the RAID version of the drive which appears to be slightly different than the regular drive. You can however get a 36GB 15k non RAID drive as a third drive. Huh?

Once again, any enthusiast or business person spending their own money on a SCSI system, is not going to by it preinstalled in a Dell system (or HP/Compaq even less likely), so those prices are worthless.

Just to add, if you do know someone who would $400 to install 2 drives, please, please refer them to me, tell them I'll cut them a break and do it for only $300.

 

[dullard]

<< Dell's site is messed up too, you can't get a 36GB 15K drive as a second drive unless you get the RAID version of the drive which appears to be slightly different than the regular drive. You can however get a 36GB 15k non RAID drive as a third drive. Huh? >>


I've never heard anything about a SCSI requirement that they must be RAIDed to use two SCSI drives (I only use 1 SCSI drive in each of my machines). That must really suck or maybe you are wrong. The only requirement from Dell about getting a 3rd drive to mix SCSI and IDE is that you must purchase a SCSI cable for $49. No where does it state that you must purchase their expensive RAID cards.


<< Once again, any enthusiast or business person spending their own money on a SCSI system, is not going to by it preinstalled in a Dell system (or HP/Compaq even less likely), so those prices are worthless. >>


Dell and other manufactuers make base machines at far less than the price that anyone can legally build on their own (software, software, software). They then charge a fortune for everything beyond the base. They charge triple for memory, double for video cards, and double for extras like a SCSI drive. That is where they make their money. This whole thread was specifically about NON-enthusiasts who don't home build their own machines. These NON-enthusiast people frequently pay the high costs for the extra memory, video card upgrade, or drives.

The fact is, even if you install them yourself, they cost more. Typical use of computers (loading a game, playing a game, writing an email, viewing the web, storing MP3s, etc.) all get little benefit from SCSI. And thus even most enthusiasts don't spend the extra money to save a fraction of a second per file. If SCSI drives came down in price, then almost everyone would have them since they are faster for small files.

 

[mjolnir2k]

wow, kind of sensing a AMD vs. Intel type situation here, as we seem to have two loyal camps. Is one better than the other....hard to say. Seems to depend on what criteria are you using to make that judgement. Price, performance, ease of installation, accessability, expansion???

all valid points, but for now I will be staying ATA. (Cost to performance seems like the best combo with this setup considering I am ALREADY using ATA)

Thanks for the information about SCSI though. I enjoy knowing what my alternatives are. Maybe my next system...

Thanks for the lively debate all.

 

[wurmyhi]

Yeah, I could see how it'd look like an AMD vs. Intel situation....too much emotion, not enough thought.

For most PC folk, ATA is the only way to go due to performance/price advantages.

SCSI is great if:
1) Your box is often disk-bound, meaning that your box is spending too much time waiting on disk access.
2) You need LOTS of storage tied to 1 box (which may contain more than 1 CPU).
3) You are willing to pay the steep premium for the benefits.
4) You have a lot of drives on the SCSI chain.

A SCSI chain w/several physical drives (representing 1 logical drive to the OS) is pretty fearsome. <- Is there an IDE conspiracy here suppressing that fact? But, unless you're willing to pay for it, it's a moot point.