SATA versus SCSI (In Server)

albanga

Hi guys!

Just wanted to get peoples opinions on a little debate we are having.

The subject line pretty much speaks for it. We are about to purchase a new mail server and are thinking what HDD to go for. We will be implementing RAID5 over about 4 disks and was wondering what you thought was the best option.

From my understanding SCSI is better performing and does not work so much throguh the CPU. The problem is its extremely expensive and when you do buy a drive you get hardly any space for it.

SATA does not perform as well but its much cheaper to get massive size drives. Im also not to sure but i am under the impression that SATA is not hot swappable, but i am definately no expert on the matter.

Both have there PROs and CONs but i would love to hear peoples thoughts. Hopefully this doesnt start an all out war!

davenport

You've pretty much laid out the pros and cons, so I can't really add much to that. The only information I can add is about Sata drives being hot swappable. I won't say that all vendors are cause that'll probably come back and bite me in the @$$ but I've worked with plenty that are.



I would say that I'll be in the minority here but I would cast my vote for Sata drives. I've got a pair of 10k rpm sata drives that are a decent size, and pretty darn fast.

seuss_ssues

Well your decision is going to be based on your needs and budget.

Personally i like this type of drive configuration
5 drives total.
2 drives = OS (mirrored)
3 drives = Information (Raid 5)

Should be fairly fault tolerant setup.

As far as the sata vs scsi we build alot of servers and i cant remember the last one that had scsi.

sprkymrk

If budget is what drives your decision then we can't be much help. I will say though that real servers use SCSI (sorry Seuss, no offence ).

SCSI controllers typically have their own CPU and memory. They are not only faster, but less prone to errors. You get more than extra speed with SCSI drives, which is why they are so expensive. Additionally, you can always upgrade the onboard memory of the SCSI controller to increase performance as well. If speed and price are all you are interested in, then SATA will give you more bang for the buck.

Plantwiz

sprkymrk wrote:

If budget is what drives your decision then we can't be much help. I will say though that real servers use SCSI (sorry Seuss, no offence ).

SCSI controllers typically have their own CPU and memory. They are not only faster, but less prone to errors. You get more than extra speed with SCSI drives, which is why they are so expensive. Additionally, you can always upgrade the onboard memory of the SCSI controller to increase performance as well. If speed and price are all you are interested in, then SATA will give you more bang for the buck.

Gotta agree with sprkymrk! SCSI is really where you want to go for dependability in a server. SCSI drives are just made for these type of configuration.

Though we've had to go with SATA on several clients as of late for 'cost'. They were in need of upgrading to a server and agreed to do so with the cost savings (up front savings) on SATA. THAT SAID, already have had a drive blown in a server less then 4 months old. Grant it, any drive can go out, but SATA on a server has been a concern....but just seems to be where the trend is heading....although if it's one of MY builds I will always recommend SCSI first.

blargoe

If I'm the one responsible for system downtime I will go with SCSI any day.

hanakuin

Once you aggregate the additional cost of SCSI vs. SATA over the life of the server and take in account the reliability and thouroughput of SCSI over SATA; SCSI wins. $3.50 SCSI per GB vs $.90 SATA per GB. You have to look at speed, you're comparing 15k drive to a 7.2k drive, you also have to look at the speed that you are getting from the contoller. If I'm going to run an intensive app like Exchange I wouldn't even consider SATA.

seuss_ssues

No offense taken,

We do build quiet a few systems, but in retrospect they are generally for smaller businesses as file and quickbooks servers.

albanga

Gee awesome response! Thankyou everyone for joining the debate if thats what you want to call it.

So it seems SCSI is the popular choice! Thats funny cos our supplier just told us to go with SATA. Which is strange cos he will lose money on it.

Just so you know, if we do decide to go SCSI, we will be getting 4 disks with 36GB each diskm which when you run RAID-5 only gives you around 110GB which isnt a lot of space for a mail server. Now we are no a massive company but are mail database has grown considrably over the past year with all our new staff. Our system admin thinks this is going to slow down but i just know he will regret that in 1 years time when we are getting low space messages like we get every day.

Money is sort of an issue so yeah we are taking that into account also. The thing to also consider is if we go SATA then for the same price we are looking at around 300GB with RAID-5 and the extra money saved we can uprade from Duo core to Quad core on the CPU.

So why we lose speed on the HDD we gain speed on the CPU. And yeah the HH is hot swappable so that is a bonus.

I think the key issue when it all comes down to it is dependability. I guess the way i look at it is different to how our admin looks at it. If it breaks down and we cant access mail for a day then its his butt now mine. Hopefully when one day im an admin, SATA will have the dependability of SCSI so i dont even need to worry about the argument.

Thanks again everyone for your help. These boards really do rock!

Plantwiz

albanga wrote:

Gee awesome response! Thankyou everyone for joining the debate if thats what you want to call it.

So it seems SCSI is the popular choice! Thats funny cos our supplier just told us to go with SATA. Which is strange cos he will lose money on it.

!

He'll sell more long term.....so it's a good choice

OR, he really doesn't understand the drives architecture and mechanics and sees it as 'lower' cost....something I find with my some of my reps on occasion. So, I try to stay with on-line ordering so I don't have to debate the issue for 30minutes.

RussS

After putting several servers with SATA RAID in small businesses (10 users or less) I have distinct thoughts on this.

SCSI for any servers I build for business that are running 2003 Small Buisness - doesn't matter what size the place is.

SCSI for any business that really needs high availability.

SCSI for any server where performance is needed.

SCSI for any server used in my own organisation.

SCSI for any server that will be running exchange.

SCSI for any Terminal Server

...............

Basically I will only use SATA for a home server or for a client ONLY wanting file and print sharing.

sprkymrk

RussS wrote:

After putting several servers with SATA RAID in small businesses (10 users or less) I have distinct thoughts on this.

SCSI for any servers I build for business that are running 2003 Small Buisness - doesn't matter what size the place is.

SCSI for any business that really needs high availability.

SCSI for any server where performance is needed.

SCSI for any server used in my own organisation.

SCSI for any server that will be running exchange.

SCSI for any Terminal Server

...............

Basically I will only use SATA for a home server or for a client ONLY wanting file and print sharing.

C'mon RussS, don't keep us guessing, which do you really prefer?

albanga

And the winner is...........*Drum Roll*..........."The envelope please"..

SCSI!!!!

I sent my boss the link to this forum and everyones passion for the SCSI has one him over. We have decided to go with 4 drives in a RAID-5 set-up. Whilst the costs are far far greater and we lose lots and lots of space the speed and reliability ultimately became the match winner.

Cheers to everyone for you feedback!

We will re-open the debate next time when we debate SCSI Versus SATA3.

Plantwiz

Congratulations!

Now the million dollar question....which brand did you select?

I'd vote for Seagate (FWIW) (now that Maxtor is w/ Seagate...and Seagate has a good track record anyway).

plettner

I can't say I like SCSI but it'd have to my choice for servers where reliability and performance are concerned. As mentioned by another poster, you can get RAID controller cards which have 512MB for caching which just blitz everything else.

I would use the SATA drive for light duty servers (e.g. we have a DELL SC420 which does nothing other than send small text files to a server in New Zealand). If the SATA drive goes down, no worries - I'll just duck off to the shops and buy a new one for $100 and reload the image.

But I can see SATA's attraction - smaller cables, no SCSI IDs to worry about, no termination, and you get 300GB drives for $180.

plettner

Plantwiz wrote:

Congratulations!

Now the million dollar question....which brand did you select?

I'd vote for Seagate (FWIW) (now that Maxtor is w/ Seagate...and Seagate has a good track record anyway).

Segate does make some good drives, especially for the money. They'd be my choice too.

macdude

My vote is scsi and will always be scsi in servers, unless you are on a very tight budget. Now since they have serial Attached scsi out, that just sweetens scsi.


I agree 100%, segate drives rock. Never had a problem with them.

garv221

SCSI in a server is not expensive, it's a price you must pay to have a reliable server and infrastructure. Anything below SCSI is just cheap in quality and below industry standard for servers. The cost is just a drop in the bucket when considering how valuable data can be.

As far as hard drives I agree with Plantwiz. Xeon is a must, I run only Seagate, I always run a raid 5 and have gold 4hr 24/7 support from Dell with a tech install on every server I manage. Look into the Dell Power Edge servers. Never had issues with them, I run the 6850's,2600's, power vault and 1950's. You can always add more space on a secondary controller.

http://www.dell.com/content/products/category.aspx/servers?c=us&cs=555&l=en&s=biz

sprkymrk

garv221 wrote:

SCSI in a server is not expensive, it's a price you must pay to have a reliable server and infrastructure. Anything below SCSI is just cheap in quality and below industry standard for servers. The cost is just a drop in the bucket when considering how valuable data can be.

As far as hard drives I agree with Plantwiz. Xeon is a must, I run only Seagate, I always run a raid 5 and have gold 4hr 24/7 support from Dell with a tech install on every server I manage. Look into the Dell Power Edge servers. Never had issues with them, I run the 6850's,2600's, power vault and 1950's. You can always add more space on a secondary controller.

http://www.dell.com/content/products/category.aspx/servers?c=us&cs=555&l=en&s=biz

Same experience here with Dells and Seagates. No problems - ever.

JDMurray

garv221 wrote:

SCSI in a server is not expensive, it's a price you must pay to have a reliable server and infrastructure. Anything below SCSI is just cheap in quality and below industry standard for servers.

This is a myth perpetuated by the hard disk industry to justify inflated prices for SCSI technology. Disk size and age have more to do with drive reliability than its interface technology. For example, an 80GB SCSI drive is no more reliable than an 80GB SATA drive of the same age, and SCSI drives are not manufactured with better tolerances or materials than are found in 10K SATA drives.

Without their interface, SCSI and SATA drive are more similar than they are different. All drives are more likely to fail when they are very new and very old, which is why you should always burn-in a drive for several hundred hours before you use it in a production environment. Heat and usage patterns are not big factors anymore because, over the years, drives have been increasingly designed and manufactured to tolerate high heat (as in laptops) and extremely high utilization levels (as in Internet servers). A far more accurate predictor of failure is the number of platens and heads the drive has and not its I/O interface.

IMHO, unless you need the data throughput that top-of-the-line SCSI systems deliver, a 10K SATA solution will give up a far better bang for the buck and be just as reliable.

hanakuin

As long as we are on the subject of reliability: http://www.computerworld.com/action/article.do?command=viewArticleBasic&articleId=9012066 this is an interesting article about HD failures. A hard drive is a hard drive as far as failure rates go. But when we look at interfaces and what the server is being used for, that is a different story. I still run SCSI on all servers, no matter what I'm using it for. SATA may be fine for small shops where there are limited users accessing a server, or if the server is a single purpose machine that doesn't really have users accessing it. Everything I have has at least several hundred users, some thousands of users accessing them, SCSI is definantly the way to go.

TechJunky

Defiantly SCSI for a server. Sata does really well for burst transmission but for constant transmission SCSI will defiantly win. I have a cheaper server, 6 hot swappable SCSI Ultra 160 drives on a Perc3Di controller and all the benchmarks I have done with just the 160 drives beat the raptor sata drives out there. I havent compared them against the new SataII 3 GB/s drives, but I bet the ultra320 drives would be pretty darn comparable.

I am using 15krpm drives, not the standard 10krpm.

sprkymrk

jdmurray wrote:

garv221 wrote:

SCSI in a server is not expensive, it's a price you must pay to have a reliable server and infrastructure. Anything below SCSI is just cheap in quality and below industry standard for servers.

This is a myth perpetuated by the hard disk industry to justify inflated prices for SCSI technology. Disk size and age have more to do with drive reliability than its interface technology. For example, an 80GB SCSI drive is no more reliable than an 80GB SATA drive of the same age, and SCSI drives are not manufactured with better tolerances or materials than are found in 10K SATA drives.

FWIW the stuff I have read shows the Mean Time Between Failures for SCSI drives is about 15 years, while the MTBF for SATA is closer to 6 years. On top of that, the SCSI drives were subject to harsher and more demanding environments than the SATA drives. That said, no one keeps drives for much more than 6 years in a production environment anyway.

JDMurray

sprkymrk wrote:

FWIW the stuff I have read shows the Mean Time Between Failures for SCSI drives is about 15 years, while the MTBF for SATA is closer to 6 years.

Never trust a drive comparison made by a drive manufacturer or anyone with a financial interest in the drive industry. The metrics published by drive manufacturers are not necessarily accurate because they are difficult to verify unless a very large sample set (>1000) of drives is tested. The drive's metrics, such as MTTF, are simply marketing information used to make one manufacturer's drive look better than the others.

Many of these studies will compare the top-of-the-line SCSI drive to a bottom-of-the-barrel SATA or EIDE drives. In any reliability comparison there must be an assurance that drives of similar qualities were tested. Many lower-end SCSI drives are electro-mechanically similar to the same EIDE drives from the same manufacturer (I'm not sure about SATA), and have similar reliability under the same operational conditions and after the same amount of burn-in time.

I personally love SCSI myself, but I think the drive industry for years has purposely mislead the public on the quality and reliability of SCSI drives in order to keep the prices of SCSI technology unreasonably inflated. But I'm not complaining, as this is one of the forces that helped create SATA, and I am looking forward to SATA 3.0.

sprkymrk

I'm not sure if that was a manufacturer study or third party - either way point taken. However it is also notable that most SATA drives come with a one year warranty, while many SCSI drives will come with a 3-5 year warranty.

Another point in favor of SCSI is the ability to use up to 16 devices per channel. I have yet to see a computer/server with more than 4 SATA ports. If you want a nice RAID setup a minimum of 5-6 drives is mandatory IMO.

plettner

sprkymrk wrote:

However it is also notable that most SATA drives come with a one year warranty, while many SCSI drives will come with a 3-5 year warranty.

Seagate and Western Digital both offer 5 year warranty on their SATA drives (at least here in Australia). That's why I only run these 2 brands. I'm not sure about Samsung and Hitachi, etc.

sprkymrk wrote:

Another point in favor of SCSI is the ability to use up to 16 devices per channel. I have yet to see a computer/server with more than 4 SATA ports. If you want a nice RAID setup a minimum of 5-6 drives is mandatory IMO.

All the motherboards I have purchased in the last 2 years (from Asus and Gigabyte) have had at least 6 onboard ports. 4 from the Intel Chipset and another 2 or 4 from a third party vendor. Admittedly these are high-end desktop boards. i can't speak for board specifically for servers.

RussS

Time to change my thoughts on this ...

I flipping HATE SATA RAID .... end of story

TechJunky

Can you get hotswappable SATA Drives?

Hotswappable technology with SCSI has been around Forever...

Just another thing to think about.

plettner

TechJunky wrote:

Can you get hotswappable SATA Drives?

Hotswappable technology with SCSI has been around Forever...

Just another thing to think about.

Yes. However, the controller must be hot-pluggable capable. The original design of SATA was to make a hot-swappable drive system.