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scsi vs. ide

Posted on 2000-04-19
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I need to replace a file/print server machine.  Which would be faster?

A) a standard P III 600 scsi hd system

or

B) a fast P III or Athlon 800+ ultra ide hd system

Both systems would be equiped with a raid adapter for mirror only and running NT 4.0.  I am trying to compare "real" or "noticable" speed/value/performance issues.

Thank You!
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Question by:current1
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by:hhamster
ID: 2732693
TIP: SCSI is better when you have many HDDs. In just one there is not a big difference between a system with an EIDE disk.
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by:Ted22
ID: 2732718
Check the transfer rates and access times on the hard drives. Don't be fooled by ata66 claims that are only for what is in the cache on the hard drive.

If your going to run mirroring with NT and ide make both hard drives masters, one on the primary and one on the secondary. If you have both drives on the same cable performance is greatly decreased.
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by:pjknibbs
ID: 2733537
If *both* systems are using a RAID adapter, surely you're going to be using SCSI by default? (I know you can get an EIDE RAID controller, but you'd be restricting your upgrade options).
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by:j2
ID: 2734254
I would say the performance of the CPU's are not an issue here, both systems are powerful enough, or why not builkd a system on two Celeron500 on a abit bp6, much cheaper then a i600 athlon800). I would always choose SCSI unless the following is true.

"You can achive the storagespace needed by two disks and will never need to upgrade the capacity, and do not require hot-rebuilds (then again, you cant rebuild a stripeset anyway)"

If that was true, i would buy a Promise controller, and two IBM GXP disks (fastest EIDE/ATA66 disks i know off), put one on each bus on the Promise and live happily ever after.
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by:fremsley
ID: 2734511
I would recommend the SCSI solution, not for performance reasons but because SCSI drives tend to be optimized for serves, i.e. machines that run 24 hours 7 days a week.
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by:j2
ID: 2734549
Not true, it is the same hardware apart from the interface bits. Compare a IBM GXP with one of IBM's 7200rpm scsi devices and you will see. However, there are no 10.000rpm IDE drives available, that i can agree to.

We run a BAAN server supporting about 50-70 developers on a deskpro with IDE disks, it is just as fast as any two disk UW-SCSI setup.

Also note that about 14% of the traffic on a SCSI bus is adress resolution / handshaking / disconnect and reconnect announcements this is something IDE doesnt have. And if you use the promise controller and give each drive a dedicated bus, the fact that IDE does not have disconect/reconnect or CTQ (Command tag queue) is also eliminated as a factor.

Yes, i still prefer SCSI, but the fact that the drives would be optimized for 24/7 usage in a server is not a factor for that decision.
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by:1cell
ID: 2735248
I agree with J2 regarding the processors.  PIII600 or Athlon?  How many users will be printing at a time here?  I have a client with a 50 station network and their print server is only a 233 but has 128MB of RAM.  I noticed that you hadn't mentioned anything about RAM but it will make a bigger difference than a mega-dollar processor.

to add to the debate, the newer ATA66/UDMA66 standard is bringing IDE up to par with the SCSI.  ATA66 has become a standard and it's pretty quick and affordable.  when you look at the cost comparisons for setting it up and the multiple RAID solutions out there, it makes it hard to spend the extra dough for SCSI unless you know you really NEED it.  

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by:j2
ID: 2735606
BUT no matter which way you look at it, EIDE/ATAPI/ATA systems is _worthless_ the moment you have more then one device per bus.
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by:johan041700
ID: 2736382
ata 66 may be faster sompaired to an old low end scsi, but the up to date standards in scsi now are much much faster (not to mention far more stable) as the ultra/dma66. Simple,
ultra/dma66 equals max 66MB transfer/sec. utra2/scsi equals 80MB/sec.
Fibre channel equals 100MB/sec
scsi160 equals 160MB/sec
And the top of the bill: scsi320 (a double scsi160) yes ---> 320MB/sec

Many forget that most ide HD sustains (and are fluctuating around) in reality a transfer of +/- 30 MB/sec. scsi is always stable at max transfer.

The best solution i think would be a cheaper CPU, lots of RAM, fast printer. scsi depends if you are willing to spend the money on a fast scsi system or not. scsiHD are more expensive to.

anyway: read about it on:
http://www.adaptec.com/technology/overview/ultra160.html
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by:j2
ID: 2736408
"scsi is always stable at max transfer. "  not true, it suffers from the same limitations as any disk system.

Now, i know scsi320 et. al. is extremely fast.. now, find me a solution where a _single_ drive can actually obtain that rate.  If you read my posts, i have never said ide was superiour outside a _very specific_ scenario.
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by:johan041700
ID: 2738599
hoi,

correct me if i'm wrong: stability in data transfer is one of the major reasons why scsi sytems are preferred for CD-RW, not?
scsi320, no
scsi160: seagate cheetah ST336704LWV 160MB/sec transfer rate. if you pull of system interrogation time, there's still +/- 140MB/sec transfer remaining.
Anyway, i will directly agree with you there are cheaper ways for a print server.

i would chose scsi, like fremsey says, scsi material is more suitable for 24h/day use.
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by:j2
ID: 2739278
"stability in data transfer is one of the major reasons why scsi sytems are preferred for CD-RW, not? "

Nope, thats because SCSI doesnt lock the bus, enabling you to actually WORK with the system at the same time.

"160MB/sec transfer rate" Yes, thats the buffer burst rate, so?

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by:johan041700
ID: 2739709
---> j2

Stability in the data transfer is one of the main reasons why you don't get buffer underruns during the burn process. I know several people who had a ide writer, buffer underrun, changed to scsi, no problem. (to be honest: exept for myself, i experience some problems.)

So, what you are saying is that +/- 160MB/sec isn't achived? Why would seagate (and any other HD developer) do spend millions in research, just to sell HD that doesn't do what it needs to do? And more, why would so many companys spend hard earned money on such expensive drives, if they could achive the same with hard drives that are a lot cheaper???

Anyway, i think for current1, a lot of RAM would be allso one of the main factors to take into consideration.
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by:j2
ID: 2739714
You are still mixing apples and pears when saying buffer underrun is a problem directly resolvable by changing to IDE there are tons more factors. And i do not think CD-recordables are even a factor in the current discussion.

"So, what you are saying is that +/- 160MB/sec isn't achived?" Sure it is, its just the same as saying "Hey, i can rev my car engine up to 9.000 rpm"

Do the math on such a drive H/C/S - Bus transfer - Speed of onboard controllers - Speed of cache - etc etc etc. These facts becomes pretty interesting if you (for instance) are tasked with building a 0.5TB oracle silo.

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by:j2
ID: 2739726
And just to prove my point

http://www.storage.ibm.com/hardsoft/diskdrdl/ultra/ul36lzx.htm#Prodspecs

The fastest drive IBM has (an ultra-160+) has an INTERNAL (platter -> head -> cache) transfer rate of 160MB/Sec, and an EXTERNAL (cache -> BUS) rate of *drumroll* 22.1-37.4 MB/sec

I rest my case.
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by:j2
ID: 2739734
even more interesting is this

 
Media transfer rate 280-473 Mbits/sec which is the maximum speed it can push data from the disks to the cache.

----

But it equates pretty well to the specs/envelope of US160. Ill leave it as an excercise to the reader to figure out why you would want to have a bus that is 8 times faster then any device made.
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by:johan041700
ID: 2740582
---> j2

I guess i'm not to beautifull to tell that you're right. I have to thank you j2. I learned something today.
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ViRoy earned 50 total points
ID: 2744859
heres what you want to have for optimal file/print server performace...

#1, disk access time obviously should be at its fastest for file servers...
SCSI is the most reliable and fastest way to go since it has its own controllers and can act independently from the motherboard and OS unlike IDE.
depending on how much you have to spend will determine just how fast you can go... you can get a SCSI hard drive that does 60mb/sec for quite cheap while IBM makes a 32gb HD that does 280mb/sec and costs $1800.. best way is to compare and research a few drives before deciding.

#2, i would DEFINATLEY reccomend the ATHLON system, processor speed is not the true key here, the advantage you will achieve over the PIII is the actual speed of the motherboard which can be a bottleneck on some systems (BUS speed). a PIII's maximum speed is 133mhz while the Athlon's is a gauranteed 200mhz which makes a DRAMATIC difference.

#3, RAM RAM RAM!!! slap a absolute BARE MINIMUM of 128mb in there (256 reccomended), RAM speed wont be very important considering RAM will always be faster than your network connection, PC133 is reccomended but PC100 is perfectly fine.

#4, if you are using multiple hard drives (which you say you are mirroring) for redundency and backups...
you can more than double the speed of the hard drives by using Stripe Sets with Parity (RAID 5) instead of Mirroring.
to do this you will need a minimum of 3 hard drives. the advantages of this over Mirroring is that the computer will divide files evenly among the hard drives for distribution.
IE... if you save a 60mb file, it will be stored in segments across the 3 hard drives (20mb per drive). when you access the file, all three drives work together to serve that file along with any other file requests instead of 1 hard drive trying to do all the work...
so as you can see you can increase hard drive access times incredibly.

along with the increased access times succeded through stripe sets (RAID 5), there is excellent backup redundency... if a hard drive ever fails, all you have to do is replace it and "regenerate" it, you will then be back up and running 100% with absolutely no data loss!

the stripe set (RAID 5) feature is a standard component in Win NT and does not require any extra stupid liscences or special hardware.



if you follow these steps i gaurantee you will be quite satisfied in its performance, while at the same time impressing everyone else ;)

ViRoy
MCSE+I

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by:j2
ID: 2744907
"since it has its own controllers and can act independently from the motherboard and OS unlike IDE" - Not true. IDE has the same architecture as SCSI when it comes to how the work cycle is definied.

"while the Athlon's is a gauranteed 200mhz which makes a DRAMATIC difference" -- So, why are there no RDRAM motherboards available for athlon so you can actually USE a 200MHz FSB?

"PC133 is reccomended but PC100 is perfectly fine" - How would you use that with the 200MHz FSB you said was a plus for athlon?

"using Stripe Sets with Parity (RAID 5) instead of Mirroring"  -- First Raid5 is 'Stripe with DISTRIBUTED parity' Its a world of difference "Raid with parity" is RAID3. Also, RAID5 is slow on writes, but reads fast.

"so as you can see you can increase hard drive access times incredibly" - If you have intelligent controllers, yes."the stripe set (RAID 5) feature is a standard component in Win NT and does not require any extra stupid liscences or special hardware. " - Yes but the PERFORMANCE of software raid is catastrophic, even the "Core NT technology"-part of MCSE teach you that,  any performance increase you would gain by striping will be lost since it all has to be emulated by the CPU. The ONLY way to gain performance is via hardware raid. AND the SW raids gives NO protection if (for instance) the system crashes or the power goes out during a write cycle. Good raid hosts have battery backup, meaning it doesnt matter if the power goes out during a write, it will finish it when the system comes back up.

Jan
Designer of data storage solutions for SAP R/3 et al.

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by:j2
ID: 2745017
and above that, i really do not think ViRoys answer adds anything new to the question. and also

"the stripe set (RAID 5) feature is a standard component in Win NT "  -- Server only, not workstation. (yes, you can trick a Workstation into fixing this, but that would violate the EULA)

"280mb/sec" thats the BUS interface speed, check out the REAL speed. And actually there is a 320 interface aswell. See the link i posted a few comments up.


and i would like to elaborate on

"independently from the motherboard and OS unlike IDE." How? -- Since when does scsi have some magic that gets the data processed without the help of the buses / CPU / operating system? The thing scsi DOES have going for it is that the devices can disconnect from the datapath when executing platter I/O. And the fact that SCSI supports CTQ (Command Tag Queuing). But all these advantages are gone if you give each IDE drive a dedicated datapath and an intelligent controller. WHat scsi have left after THAT fact is that there is no solution for IDE that will have a high performance when using more then two drives / controller making IDE unsuitable for high volume storage management.

Yes, i am ALWAYS 'pro-scsi' but none of the above is an accurate description of the pros/cons of scsi vs IDE.
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by:ViRoy
ID: 2745783
j2, this is the "REAL speed"
oh yea, and thats in megabytes per second not megabits per second... as i gather your not aware of is that IBM has a tendency to outdo any pc market before its even though of...

example #1... why are iomega zip drives so popular when IBM makes a smart media about half the size of a dominoe and holds 300mb for less than 200$ ?????

example #2... are you aware IBM has successfully accomplished teleportation?? thats right, they now use that technology in a network hub that transmits data on protons that travel faster than the speed of light.. ill leave the actual mb/sec equasion up 2 you ;)

also j2, mr data storage designer :0
did u forget that NT workstation is not capable of commiting its role as a file/print server?

about the scsi vs ide thing you posted that says "IDE has the same architecture as SCSI when it comes to how the work cycle is definied." so are you saying that IDE has just as much or less load on the CPU than SCSI?
if so then i suggest you read a book.

""PC133 is reccomended but PC100 is perfectly fine" - How would you use that with the 200MHz FSB you said was a plus for athlon?"
so are you implying that those motherboards are not capable of being INCREDIBLY faster than the PIII boards? if so, i suggest you read a book.

about your disk striping babble of bashing me as much as you can... as taught by the MCT's disk striping best quality is the improved performance of disk access.

"and above that, i really do not think ViRoys answer adds anything new to the question."
i sure hope it dosent add anything new to the question, my objective was to answer it, not add more to it.

and finally, why would you post all that junk. wasting my time, your time, and everyone elses time readin it as you just made me do? and then all you do is bash me, you dont offer any alternatives or possible solution or even say that my idea was a bad or good one... i think all you want to do is offend people and bash me... so tell me WHAT WERE YOU TRYING TO ACCOMPLISH?
 



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by:ViRoy
ID: 2745815
j2, this is the "REAL speed"
oh yea, and thats in megabytes per second not megabits per second... as i gather your not aware of is that IBM has a tendency to outdo any pc market before its even though of...

example #1... why are iomega zip drives so popular when IBM makes a smart media about half the size of a dominoe and holds 300mb for less than 200$ ?????

example #2... are you aware IBM has successfully accomplished teleportation?? thats right, they now use that technology in a network hub that transmits data on protons that travel faster than the speed of light.. ill leave the actual mb/sec equasion up 2 you ;)

also j2, mr data storage designer :0
did u forget that NT workstation is not capable of commiting its role as a file/print server?

about the scsi vs ide thing you posted that says "IDE has the same architecture as SCSI when it comes to how the work cycle is definied." so are you saying that IDE has just as much or less load on the CPU than SCSI?
if so then i suggest you read a book.

""PC133 is reccomended but PC100 is perfectly fine" - How would you use that with the 200MHz FSB you said was a plus for athlon?"
so are you implying that those motherboards are not capable of being INCREDIBLY faster than the PIII boards? if so, i suggest you read a book.

about your disk striping babble of bashing me as much as you can... as taught by the MCT's disk striping best quality is the improved performance of disk access.

"and above that, i really do not think ViRoys answer adds anything new to the question."
i sure hope it dosent add anything new to the question, my objective was to answer it, not add more to it.

and finally, why would you post all that junk. wasting my time, your time, and everyone elses time readin it as you just made me do? and then all you do is bash me, you dont offer any alternatives or possible solution or even say that my idea was a bad or good one... i think all you want to do is offend people and bash me... so tell me WHAT WERE YOU TRYING TO ACCOMPLISH?
 



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by:ViRoy
ID: 2745857
sorry bout the 2nd post, i hit refresh and my browser re-submitted all the form data.
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by:j2
ID: 2746364
"oh yea, and thats in megabytes per second not megabits per second... " - read the fac sheets then. See my post from Saturday, April 22 2000 - 12:23PM. I visited the IBM storage labs a few weeks back, didnt hear anything about a miracle drive. The "IBM Ultrastar 36LZX" with a DDHS interface is the fastest thing in production, and it has a sustained transfer rate of "22.1-37.4 MB/sec" Now, what you have read is the "Media transfer rate" which is "280-473 Mbits/sec" (see http://www.storage.ibm.com/hardsoft/diskdrdl/ultra/ul36lzx.htm#Prodspecs"

"did u forget that NT workstation is not capable of commiting its role as a file/print server? " Sure it can, you can either use SMB and stick to <=10 clients, or use NFS / LPR to connect more users.

"are you aware IBM has successfully accomplished teleportation?? " - Whatever.

"that IDE has just as much or less load on the CPU than SCSI? " - IDE taxes the CPU higher, but you know, i havent seen a "IDE" drive in years, nowadays people tend to use ATAPI drives. And as with scsi a bad controller means bad performance, the Promise is a good example of a fast controller.

"so are you implying that those motherboards are not capable of being INCREDIBLY faster than the PIII boards? - They don't exist yet. There is no athlon board that provides a 200MHz memory clock, in the meantime, read http://www.tomshardware.com/cpu/00q1/000320/giga-09.html (better yet, read the whole article) and find

"There you have it! With the inclusion of Intel's 840 chipset in the Giga-evaluation, Giga-Pentium III is able to win each real world benchmark in this set. Only Giga-Athlon's pure FPU-performance is on top of Giga-Coppermine's. "

So, even tho the Athlon is is seemingly a faster CPU (and it is more advanced then the P-III) it still looses the benchmarks, since there are no motherboards / memory that can keep up with this speed demon.. and also the Coppermine range of P-III has moved the L1 and L2 caches even closer to the core, and thereby gaining quite a lot of speed.

"about your disk striping babble of bashing me as much as you can" - You still had your facts wrong when mixing R5 with R3. Yes striping is meant to speed up data access, but with distributed parity the write speed suffers a penalty. The fastest RAID architecture is raid 10 (or 1+0 more correctly) (Mirrored stripe) it is (naturally) the most expensive tho.

"so tell me WHAT WERE YOU TRYING TO ACCOMPLISH" -- Point out errors in your post.

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