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Use of IDE or SCSI drives with a NAS solution

We are currently researching purchasing a NAS solution.  We have been quoted prices from different vendors for different solution.  The basic difference between the different solutions is that one uses IDE drives and one uses SCSI drives.  The SCSI solution is about 3 times as expensive as the IDE solution (just because of the lower capacity and higher price of the SCSI drives).  I was told by the IDE vendor that IDE will peform exactly like the SCSI solution because they will have high quality controller cards with large cache buffers.  Both solutions will be configured for hardware RAID 5.  I want some opionions on the pros and cons of SCSI vs IDE.  I have always known that SCSI is a better drive than IDE, but does the cost justify the performance.  Specifically, I would like to know about the following:

- Reliability
- Write Speed
- Read Speed
- Throughput

1 Solution
Physically, IDE and SCSI drives are the same inside. The performance improvements SCSI has over IDE come from differences in the bus and the controller logic. You see the higher end 10,000 and 15,000 RPM hardware on the SCSI drives because SAN and workstation oweners will pay for it. The SCSI bus performs better under multi-tasking because all the drives on a SCSI chain are cable of operating at the same time. IDE (ATA) is a serial bus, not much different from the ST506 interface on your grandmother's IBM PC.

That said, in a NAS environment, you're putting data onto the box via the network, limiting the transfer rate to the wire speed. Even gigabit ethernet is no sweat for the sophisticated caching controllers found in today's NAS boxes. You've basically got a CPU dedicated to getting data on and off the array in you NAS box, emulating many of the functions the SCSI controller does in a workstation, SAN or server.

Reliability comes from proper cooling, selecting 'mature' high end ATA drives and raid logic. Read and write speed can be affected by which raid you use, but again, I don't think the NAS environment is going to be much affected as you're limited to wire speed on the network.

bmcclearyAuthor Commented:
So in other words, as long as we are going to stick with NAS and not a SAN solution, that the performance gains for SCSI drives MIGHT not be justified by the higher cost and that IDE drive will probably work just as well.  Is this correct?

FYI - We do plan on upgrading to a SAN solution in the future, but at this point in time, we do not need that much capability, not wish to incure the much higher cost.  For now, we just need something that will handle 1-3TB of data fairly quick and reliably.
If you go to a SAN a 'black box' NAS won't play any part in it anyway. If you wanted to buy the controllers and disks and run a NAS by attaching a CPU to the setup and upgrade to Fibre Channel connections later, you might recoup some of your investment. A NAS from quantum, maxtor or network applience will be a lot easier on the noggin now tho...
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SCSI does have higher performance than IDE in all apects, but as it's limited to network speed (usually 100mbit/sec) it really only boils down to SCSI being millionths of a second faster at responding to data requests (data fetch latency), for all that extra cost. I see SCSI hard disks fail as often as IDE.

I would definately make sure the IDE NAS you buy comes with the same amount (or more) IDE-channels as hard disks you have. eg 3 hard disk raid should have 3 channels. Anything less would most likely be a performance hit.
IDE write speeds will be affected when using IDE.  Check out this link which gives some good feedback information on write speeds for IDS.  Lso the root of this link is a very valueable source of information for what your looking to do.
SCSI is reliable, the cabling has more pins (more data flow with the ability to recall bad bit flow without affecting other cable strands)

keep the SCSI drives and Controllers the same brand

the buffering in the IDE is used to compensate for bad data bit flow (enabling it to ask for good bit flow before going into the system); caching is good, and the more you have, the better, but if SCSI also has the same or better caching and data goes into the drive with error checking in the chips of both the controller and the drive, then the data doesn't have to wait anywhere before it is used - another strand on the scsi is used to send and retrieve unusable bit flows

if you are using this raid in a high scale environment, it would be advantageous to spend more money on the initial investment than to deal with slower, less reliable hardware like IDE - regardless of how much firmware is installed; the fact that SCSI has more cabling and firmware for data bit checking will allow faster through put.

thats just my opinion...

FWIW, I am running an IDE RAID on my own box...two arrays, on two channels. Each channel has one member of an array. I am doing this because I am running H/W video editing and need the speed. The array is strictly striped. My mean through put on any test I can throw at it is about 60 MB/sec. There are peeks and valleys in those numbers. Can't forget latency and overhead issues on the PCI Bus.

I have clients that I have built servers for with Adaptec RAID Port III on Intel based server boards that run circles around the IDE setup in RAID 5 formation to boot! This is true of Adaptec standalone RAID card solutions too!

SCSI's advantage is the ability to essentially parallel task. If I send 100 calls to the HDD's for info and to write info those calls are performed. If I send those 100 calls to an IDE array they are performed one at a time.

IDE Advantages: Co$t! Large storage. Quick access/read times. Medium throughput.
SCSI Advantages: Multiple data access read/write. High Throughput. Vastly superior future possibilities. Easy to tie in more drives...as many as 30 HDD's! Easier to add more controllers and HDD's too. I believe SCSI Hard drives are manufactured with longevity in mind (witness IDE HDD manufacturers backing off their 3 year warranties to 1!!!). This doesn't apply in an OEM situation depending on the OEM's warranty of course!

On a final note, if you have the funding go for the SCSI! It may be a little more than you need now, but, it's good to have room to grow. This philosophy is one I adhere to!

Keeps my clients happy too...cause I'm not asked to upgrade hardware that is only 9 months old because they have grown out of it!

I hope this helps!

Handy HolderSaggar makers bottom knockerCommented:
Cheap IDE based NAS boxes are ideal for an intermediate backup solution but their main disadvantage is they normally use high capacity drives. Two low capacity drives will always be faster than one high capacity one since there are twice as many heads to get the data from. They're normally just glorified win2k boxes.

If you can afford it get a NAS box that can be SAN attached so when you do upgrade you can virtualise it's disks onto the SAN and present SAN data on the network with it.

It really depends what you want the storage for, if it's just file sharing a SAN is wasted but if you have a database then it would be silly to put it on NAS.

 Selection of storage solution is not that easy. It all depends on your organiazational needs.

 suppose if you want high end solution with faster and more reliable better to go for SCSI. but the problem with these devices are costly with less storage space.

 If your organization needs mediam storage solution with not much reliable, and speed. you better go for IDE.

 Presently IDE also doing better. But It all again depends on what is the RAID controller your are using to control IDE disks, SCSI disks.

 till now I have seen so many NAS system which are using IDE + hard ware RAID controller(3ware) is failing. But if we use this with S/w raid it is working fine the main thing is not fast.

 But if you want to dump so much (> 2GB ) of data with in minutes better to go for H/w RAID+SCSI. Other wise select the IDE ...

 Again I am saying this...It all depends on your organizational usage.

 We are NAS developers too..you can have a look on our products www.storageone.co.kr

 I think you got understood..

bmcclearyAuthor Commented:
Thanks to all for your input.  It gives us a basis to move forward with.  Chicagoan, you answered first and were very helpful, so I am awarding the question to you.  For everyone else, all of your answers were also great, so I wanted to give you points as well.  You can get these points from the following posts:

Lamdor -

PhilElder -

Eddie_Madrigal -

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