SCSI vs. IDE

[m3ch4 0]

Hey, I recently came into possession of an unused pc that the owner couldn't get running, they told me that if I could get it working I could keep it (and even if I can't, I've still got it =P )so I've been going through the innards (I think the problem is the power supply, testing parts tommorrow) and I've come across some scsi stuff. A card and a pair of hard drives.I've never used scsi hdds before, what is the difference between scsi and ide and how exactly does scsi work?

[miCRoSCoPiC^eaRthLinG 0]

Hi,
Firs tof all - both of them are Hard Disk Drive controllers, althought SCSI was desinged to do much more than simply control Hard Drives. SCSI was a mix of the IDE controller plus USB ports (not really - but imagine the marriage of both these functions) - giving rise to a device that could drive your HDD at high speeds as well as provide an interface connect external devices like CD-Rs, Scanners, Cameras etc. to your system. IDE could ONLY deal with your HDDs.
SCSI card's were supposed to be primarily for very high-performance systems - like high stress network servers, where IDE would have failed really bad. IDE was more of a desktop standard. Now with the coming of SATA interface, the difference is kind of blurred out. You can find more informations at these links:

1. http://forums.xisto.com/no_longer_exists/#
2. http://forums.xisto.com/no_longer_exists/
3. http://forums.xisto.com/no_longer_exists/
4. http://forums.xisto.com/no_longer_exists/

Hope this helps.

Regards,
m^e

[madcrow 0]

While the SCSI vs IDE thing is sort of a moot point for modern ultra-fast computers, SCSI is good for PCs with less powerful processors because it takes the work of dealing with disk and CD stuff off the main CPU and gives it over to a dedicated controller. IDE just uses the main CPU, so you can't do as much with it on an older computer. I especially notice the difference in CD speed. On my old P3-800, I get MUCH better transfer rates using SCSI than I do with IDE, even though the drives are theoretically the same speed. I don't notice as much of a difference with hard drives, but I can see it a bit on my P2-300. If the system you got is a P3 or older, definantley stick with SCSI. Just remember that NEW SCSI drives cost twices as much as their IDE counterparts. Try to get used SCSI drives off of E-bay. It's what I do and it works fine.

[m3ch4 0]

Thanks guys, that helps a ton, I'm definitely going to be holding onto this stuff for the next computer I build

[slawoszs 0]

What is better, scsi or SATA??For PC SATA but Im not sure...

[RGPHNX 0]

Hi all,not much I can add except that you should definitely hold onto the SCSI HDs because they're probably very fast drives. Also.. SCSI drives are much easier to use for RAID configurations & data duplication/ backup etc.Hope this helpsRGPHNX

[Ocelot357 0]

Hey, I recently came into possession of an unused pc that the owner couldn't get running, they told me that if I could get it working I could keep it (and even if I can't, I've still got it =P )

 

so I've been going through the innards (I think the problem is the power supply, testing parts tommorrow) and I've come across some scsi stuff. A card and a pair of hard drives.

 

I've never used scsi hdds before, what is the difference between scsi and ide and how exactly does scsi work?

<{POST_SNAPBACK}>

Forget scsi. It takes forever to boot. I used Cheetahs for a while, but Ide are just great. I do video and audio editing and I use Ide drives. I have no issues at all. Actuall, My cheetah drive was only 1 year old before it crashed and i lost all the information. I have never had an Ide drive completely crap out.

[yordan 10]

Depends if you want to do familial or professional work.for professionnal work, you need a lot of throughput, so most of professional servers have SCSI disks.Family computers have IDE disks. They are far cheaper, and boot faster. So, if you have professional need for a lot of devices (significantly more than 2) and a lot of disks throughput, you will have SCSI disks.At home, you will have one or two IDE or SATA disks.

[wutske 0]

SCSI disks are also made for servers, they can work actively 24/7, no IDE would be able to do that w/o errors or failures. SCSI drives can also work under much more stress (no IDE drive would survive 85°c working temperature (air-co failure in small server room)), plus there are also some gimmicks wich in SATA terms is called Native Command Queuing, it can help speed up things, but hardly for the average users.Ow, and other thing, the fastest SCSI drive spins at 15.000rpm, while the fastest, SATA/IDE drive spins at 10.000rpm (WD caviar). All other IDE/SATA spin at 7200rpm, wich gives much higher latencies then 15.000rpm (ow, and 15.000rpm is noisy).Hope this helped a bit more.

[Logan Deathbringer 0]

I once had a P3700 that was pure SCSI because I hosted a gaming server for a "clan" I belonged to for Q3. On the very rare occasions I had to reboot it I honestly didn't notice any real difference between its boot speed and a similar computer I had, it had very similar specs except it was IDE based. Now when I quit hosting the server after my main computer went to computer heaven and I canibalized both to have a "Hybred" IDE/SCSI computer I then did notice a major boot speed difference since trying to run SCSI/IDE on the same system is like walking along the top of a picket fence at times.Only then did I notice any real problems. I would still take a full SCSI system over IDE if I could afford to build one, even with SATA coming out I'd take the SCSI.

[kam1405241509 0]

I once had a P3700 that was pure SCSI because I hosted a gaming server for a "clan" I belonged to for Q3.  On the very rare occasions I had to reboot it I honestly didn't notice any real difference between its boot speed and a similar computer I had, it had very similar specs except it was IDE based.  Now when I quit hosting the server after my main computer went to computer heaven and I canibalized both to have a "Hybred" IDE/SCSI computer I then did notice a major boot speed difference since trying to run SCSI/IDE on the same system is like walking along the top of a picket fence at times.

 

Only then did I notice any real problems.  I would still take a full SCSI system over IDE if I could afford to build one, even with SATA coming out I'd take the SCSI.

1064319281[/snapback]

The next-gen SCSI is called SAS. You can plug in SAS and SATA drives into a SAS controller to get the best of both worlds (cheap large SATA data drive + 15k RPM SAS boot drive). SAS/SCSI's TCQ is more advanced than SATA's NCQ in terms of queue depth and more advanced caching algorithms for parallel tasks.

 

For parallel data transfers with low CPU utilisation, SCSI rocks.

[kam1405241509 0]

SCSI disks are also made for servers, they can work actively 24/7, no IDE would be able to do that w/o errors or failures. SCSI drives can also work under much more stress (no IDE drive would survive 85°c working temperature (air-co failure in small server room)), plus there are also some gimmicks wich in SATA terms is called Native Command Queuing, it can help speed up things, but hardly for the average users.

Ow, and other thing, the fastest SCSI drive spins at 15.000rpm, while the fastest,  SATA/IDE drive spins at 10.000rpm (WD caviar). All other IDE/SATA spin at 7200rpm, wich gives much higher latencies then 15.000rpm (ow, and 15.000rpm is noisy).

 

Hope this helped a bit more.

1064319276[/snapback]

And SCSI will soon make the leap to 22k RPM. I found a few pages refering to these drives, but they are still research/lab prototypes! My guess is we'll see them when drives move to perpendicular magnetic recording techniques.

[kam1405241509 0]

Forget scsi.  It takes forever to boot.  I used Cheetahs for a while, but Ide are just great.  I do video and audio editing and I use Ide drives.  I have no issues at all.  Actuall, My cheetah drive was only 1 year old before it crashed and i lost all the information.  I have never had an Ide drive completely crap out.

1064318281[/snapback]

I'm not sure what you mean by it taking forever to boot. If you mean the SCSI controller doing a search of the SCSI bus, then this is a controller BIOS issue (I think I remember modern LSI BIOS's could be set to check only specific ID's, and you could disable channels etc too .. I can have a check later next week if someone wants to know for sure).

 

If you mean throughput/access times ... I found my 15k.4 was much faster at booting both Windows & Linux cf my WD 250GB SATA drives.

 

The only downer is that the caching algorithm is aimed at server (parallel) task machines, so WD Raptors do better for desktop tasks in this scenario (single threaded). However if you have an SMP machine, doing many things at once, my feeling is that SCSI is useful here .. but that's a subjective assessment!

[kam1405241509 0]

While the SCSI vs IDE thing is sort of a moot point for modern ultra-fast computers, SCSI is good for PCs with less powerful processors

...

I get MUCH better transfer rates using SCSI than I do with IDE, even though the drives are theoretically the same speed.

...

1064303864[/snapback]

I agree. SCSI really comes into its own when you have large amounts to transfer. IDE will have to use the CPU alot to send that data. SCSI also has more commands to cope with more complex situations. It is also especially useful when streaming several bits of data from different parts of the disk, but that's also partly to do with having large disk & controller caches, as well as really decent controllers themselves.

[kam1405241509 0]

A side-point that might be of interest to some people here is that 3Ware make their Escalade series of SATA controllers .. aimed specifically at SCSI-like performance. They have benchmarks on their website/PDF as do THG (Toms Hardware Guide).I remember reading a comparison review of SATA controllers, incl some onboard motherboard ones, and there was a big difference in performance. This is one of the reasons why SCSI is often looked at as being much much better than SATA, but this is going to be the case when comparing a 5Dollar motherboard chip and a 300Dollar SCSI PCI-X card!Still, I do think SCSI gives a "smoother" experience during high-CPU-loads or serious multi-tasking (e.g. running several VMs at once).