Need help picking SAS vs SATA

[sebastian869]

Does any one here have any expereince with sas(Serial Attached SCSI) hard drives?
Are they worth the money? I saw some on newegg for example Fujitsu MBA3300RC 300GB 15000 RPM 16MB Cache Serial Attached SCSI (SAS) Hard Drive - OEM $339.99 and HITACHI Ultrastar 15K300 HUS153030VLS300 (0B22132) 300GB 15000 RPM 16MB Cache Serial Attached SCSI (SAS) Hard Drive - Retail $319.99 Though Ive read of the last one not having it seen by the Asus P6T6 mother board. I was thinking of getting the P6T delux specifically for the native SAS controller. To me it does not sound like a bad deal particularly when the Western Digital VelociRaptor WD3000HLFS 300GB 10000 RPM 16MB Cache SATA 3.0Gb/s Hard Drive - OEM is $229.99. Was wondering what you guys think on the topic.

 

[sub mesa]

If you need speed, go for SSDs (like Intel X25-M or Intel X25-E). If you need storage, go for larger SATA disks. Or use a combination of both.

I'd avoid SAS; SSDs will burry mechanical disks in both performance and reliability, two key points to go SAS disk instead of a SATA disk. SSDs, even todays offerings, already surpass SAS disks in both of these points, and more because power consumption and thus heat is at an extremely low level. Its also prone to vibrations and has little power requirements on the power supply (mechanical disks use 30-40W for spinning up, which can get annoying with more than 8 drives in one system).

 

[chef7734]

Problem is a ssd that performs at the level of sas drive will be in the 500 to 800.00 range for a ocz vertex 250gb.

 

[specialk90]

There are several problems with SSD's right now. There is a reason businesses that rely on servers have not switched from SAS 15k drives to SSDs even though the numbers look good on paper. SSDs have major performance problems if they are not looked after and tweaked constantly.

What do you need higher speeds for? If its just for Windows or another OS plus programs, 15k drives are not worth it. If you need better error protection, then SAS is the way to go. SAS drives have a far lower rate of errors than do Sata drives. If your PC will be running 24/7, then you want SAS drives or other "Enterprise Class" drives such as the Velociraptor, ES.2, RE3 and Ultrastar.

 

[sub mesa]

Major performance problems? You mean the 2-phase writes or the JMicron write latency bug? Intel X25-M doesn't have that and can do random IOps still like 100 times better than a SAS disk. HDDs do have firmware and controllers that has been tweaked for decades; with SSDs they have to invent a different way of doing things right now. And JMicron just didn't get the design right, Intel did have a good design without any strong weakness making it an excellent choice since it surpasses HDDs by any means except for capacity and price per capacity.

That is why HDDs will still have usage; people would have an SSD for basic storage space (the system disk plus installed apps) and a HDD could act perfectly as backup or storage/data/download disk. HDDs still have good sequential speeds even though they will find themselves against 1000MB/s PCIe flash controllers. For the consumer, it means they leave the HDD outside of their performance experience meaning a much more responsive UI and faster operation in everyday task.

For servers, a single SSD or a few in RAID0 (why not SSDs do this internally already) might replace dozens or hundreds of SAS disks; all needing high amounts of power and thus needing additional cooling etc. No SSDs will be a relief by everybody.

 

[sebastian869]

If you need speed, go for SSDs (like Intel X25-M or Intel X25-E). If you need storage, go for larger SATA disks. Or use a combination of both.

I'd avoid SAS; SSDs will burry mechanical disks in both performance and reliability, two key points to go SAS disk instead of a SATA disk. SSDs, even todays offerings, already surpass SAS disks in both of these points, and more because power consumption and thus heat is at an extremely low level. Its also prone to vibrations and has little power requirements on the power supply (mechanical disks use 30-40W for spinning up, which can get annoying with more than 8 drives in one system).

I agree, but take cost into account. U cant buy a 500 gig SSD and if you could it would be well north of 1k. So if you add cost into the equation what do you think then, as I agree SSD is the future but its not practical now.

 

[sebastian869]

Moral of the story, do you guys think 2 raptors (300 gig) raid are better or 2 SAS (HITACHI Ultrastar 15K300 HUS153030VLS300 (0B22132) 300GB 15000 RPM 16MB Cache Serial Attached SCSI (SAS) Hard Drive - Retail $319.99) raid are better?

Also, Is the Asus P6T delux sas on board controller a good one?

 

[sub mesa]

And you think SAS is cheap?

"I was thinking of getting the P6T delux specifically for the native SAS controller"

Unless you know what tagged command queueing is and what impact it has on server performance, there is totally no reason to go SAS. You'll waste money you could spend on a good SSD. A HDD will always be slow, no matter howmuch rpm, how much MB/s it can do. Its mechanical; what did you think? Something has to *PHYSICALLY MOVE* in order to get your data; that can never be as fast as the other electronics in your computer.

Intel X25-M 80GB is like 350 euro here, so put two of those in RAID0 and you have a very fast 160GB disk. If you really need more space, there is no option available to you at reasonable cost and still offering great performance. A Velociraptor would be your best bet then, on the normal SATA controller - always use the chipset controller no add-on controllers as they add latency.

So my advice is don't waste money on technology that does not suit your needs. While SSDs may be new they are already so much better than mechanical disks. And you need no specific controller for this; and you can use RAID0 without any significant risk; SSDs dont fail. If they fail, its due to ESD, physical trauma or exceeded write cycles lifespan.

 

[sub mesa]

Also, server HDDs like SAS disks are optimized for server (multiqueue) I/O and will have sub-optimal performance for desktop/gaming/workstation tasks. The Velociraptor 10K SATA disk is really the only alternative. Never go SAS on a desktop; you wasted your money if you did.

 

[Raviolissimo]

technology has left me behind. i still like my old U-160 SCSI systems, but SATA and even modern PATA are so much faster.

i haven't had the motivation to explore SAS or the $$ to try an SSD.

maybe somebody will come out with Serial Attached SCSI Solid-state Integrated, and we'll have SASSI.

 

[sub mesa]

The only reason SAS exists is to seperate the business market from consumer SATA disks, to make sure those lucrative SAS-products keep being sold, even though SATA is a much better choice.

Google has also demonstrated that using cheap hardware is generally the best route; as it allows you to have more redundancy and due to more disks, overall more performance. I believe google is already using SSDs in their servers for over a year (May 2008).

 

[sebastian869]

And you think SAS is cheap?

"I was thinking of getting the P6T delux specifically for the native SAS controller"

Unless you know what tagged command queueing is and what impact it has on server performance, there is totally no reason to go SAS. You'll waste money you could spend on a good SSD. A HDD will always be slow, no matter howmuch rpm, how much MB/s it can do. Its mechanical; what did you think? Something has to *PHYSICALLY MOVE* in order to get your data; that can never be as fast as the other electronics in your computer.

Intel X25-M 80GB is like 350 euro here, so put two of those in RAID0 and you have a very fast 160GB disk. If you really need more space, there is no option available to you at reasonable cost and still offering great performance. A Velociraptor would be your best bet then, on the normal SATA controller - always use the chipset controller no add-on controllers as they add latency.

So my advice is don't waste money on technology that does not suit your needs. While SSDs may be new they are already so much better than mechanical disks. And you need no specific controller for this; and you can use RAID0 without any significant risk; SSDs dont fail. If they fail, its due to ESD, physical trauma or exceeded write cycles lifespan.

I hear you and I agree but I think SSD is going to be on my next build right now their too expensive and too small.

P.S. I'v seen them here on froogle at $319 sounds way cheaper then the 350 euros.

 

[sub mesa]

$319 is like 250 euro? That's extremely cheap. If its really the Intel X25-M 80GB disk.

But you have to decide for yourself if its worth it. The storage space is not alot, but its enough to hold your OS + applications. All other data you can put on mechanical HDD; but with all the system files and apps on an SSD you would really notice the difference.

In fact, i would say an Intel Atom with SSD might prove a better experience than a Core i7 with normal HDD. Why? Many times actual waiting time is because of your HDD, not your CPU. Processors are so fast already, but your harddrive is often still a major bottleneck. I feel its worth investing in because of the high performance difference. Right now you're paying like twice as much for a processor thats only marginally faster; an SSD could be many times faster and thus warrant spending money on -- in my opinion ofcourse.

I see lots of people spending alot of money on things that don't matter -- but an SSD would matter in your everyday experience. If for whatever reason you don't want to go for an SSD right now, the WD Velociraptor (2.5", 10.000rpm, SATA) is a good conservative choice.

 

[specialk90]

Sub mesa, could you please explain the benefits of using 2 X25s in Raid 0 vs just one?

The way I see it: one X25 is already lightning fast in terms of Random Access and Read & Write speeds. So, unless he has several other fast drives in Raid that can take those fast reads from the X25, more than one would be a waste.

Thanks

 

[sub mesa]

If you put two of them in a PROPER raid0 (not one with misalignments and stuff) - you should get even higher IOps performance out of it. For servers that means more transactions per second, or less servers required. For desktop that means less waiting time when starting an application or basically donig anything that causes you to wait for the I/O.

Assume a 40GB SSD costs 100 euro, assume the same type but 80GB SSD costs 200 euro, in this case there is no real difference in buying one big 80GB or two small 40GB SSDs. If you pick two of the 40GB ones you can put them together in RAID0 and have just as large a disk as one 80GB but its faster and without additional cost.

This will probably change in the future: bigger SSDs will be faster due to more 'channels' they have which can operate in parallel. But for now, probably the best you can do performance-wise is picking the smallest capacity of a high-speed SSD drive and combine them with RAID0. Since SSDs can't fail like HDDs can there is no risk of a disk crash. So RAID0 can be safely used in combination with SSD drives.

The only added risk from using RAID0 is the RAID layer itself. Luckily RAID0 is not that complicated so driver programmers can't screw this up too big, unlike with RAID5 which requires a very complicated design before it yields high performance.

What you may have meant is when copying data, the speed depends on the slowest drive in the chain: if your source (SSDs) is very fast but your destination (HDD) is very slow, you obviously won't get any real benefit. But it all depends on your situation. If you are like me -- having multiple system each with a small SSD inside and bigger HDDs in RAID for general storage - you have the best of both worlds. The SSD makes sure you can boot fast, applications dont 'hang' or cause you to wait for it to finish tasks anymore; loading a game goes noticeably faster and general performance experience improves. For your MP3's, ISOs and AVI's you better use mechanical harddrives still, and with these speed is not really important: the throughput is fixed when you are listening to an MP3 or watching a video: a faster HDD doesnt make the movie go faster, and neither would you like it to.

Also note that SSDs do RAID0 internally already (channel bonding; interleaving) so any argument against RAID0 would hit SSDs themselves too.
And lets not forget Dual-Channel memory is exactly the same idea as RAID0.

 

[mamw93]

Don't go SAS. For the same amount of money get SATA hard drives and put them in RAID 0+1 so you have redundancy and striping.

 

[bigj91]

Submesa,

great answer, sorry to hijack thread op, but i will start my own if op wants me too. I am thinking about building a server, it will run continuously for a primary care doctor's office. The server will run microsoft sql database, it will have all the old patient charts scanned and have 5 computers reading this chart information and writing new information simultaneously. so i plan on buying either a 2 intel mlc ssd 160gig or 2 hitachi ultrastar 15k in a raid 0, with sata 1TB wd installed for back up/mirror the raid drives. I am worried about the performance degradation of the intel mlc ssd, as the drive becomes full, also i do not want to spend more than US $800 for the main hard driveS. Also any recommendation on a value raid adapter? Thanks again

jc

 

[sub mesa]

Well normally your motherboard has onboard RAID already, those you should be able to use for RAID0, RAID1 or RAID 0+1 meaning you should generally avoid onboard RAID5 drivers, since those are generally of bad design (Intel ICHxR is mediocre though - and usable). If you use the onboard RAID, you don't need a controller so you can spend the money on the SSDs themselves.

So its either controller+HDDs or onboard RAID+SSDs which should give you around the same price, but HDDs have more capacity while the SSD solution would be much faster instead.

The performance degradation of the Intel X25 SSDs has been fixed and new firmware is available, and even if you don't want to do that making a smaller partition would disallow any application from writing the disk full. One helpful feature here is in Windows 7, which signals the SSD which blocks aren't used anymore, so the SSD can continue to 'be fast' by doing some write redirection tricks. I'm not sure what solution the firmware uses to fix this, but benchmarks have showed it to fix the performance issues people had completely.

If you only need two ports, the Areca ARC-1200 is a cheap choice and still a nice product. But if you were using onboard RAID you could also use three or four smaller 80GB SSDs instead. How much storage space do you really need?

 

[Ignatowski]

The only reason SAS exists is to seperate the business market from consumer SATA disks, to make sure those lucrative SAS-products keep being sold, even though SATA is a much better choice.

dual data paths, small capacitor on drive in case of power loss( so it can dump any write queued on the internal cache). there are a few more things im missing.

Also, server HDDs like SAS disks are optimized for server (multiqueue) I/O

this is often due to better controllers than better drives. but dont discount this in the home experience. people are mutlitasking far more than they used to. instead of several hundred simulateous io threads its a couple of dozen. its still the same bottleneck. any reduction in seek time is welcome.

however, i agree that sas is not really for home use. it did not help my crysis benchmarks at all. 8.(

on the business side.
unless you specifically build your app/database with using the 1 drive per lun systems then you have other risks to consider. retooling an app is something most companies arent willing to do.
personally i took a huge hit on perfomance when i converted my raid 5 from sas to sata ( on the same controller) on several of my servers. swapped the drives back and everything was happy again. other servers that run more cpu based apps did just fine.
i tried it with a few x25e's also and it was very happy. then i gave my boss a po for 100 of them and he laughed at me.

and sas is far cheaper to deal with than FC.

 

[DougRH]

Don't go SAS. For the same amount of money get SATA hard drives and put them in RAID 0+1 so you have redundancy and striping.

I agree that at this point in time a combo of both SSD and HDD are the way to got.
From what I understand about it, you really want RAID 10 which gives you both data splitting and full redundancy which apparently is is not the same as RAID 0+1 which does not.
Mechanical HDDs ALL fail eventually. Having been using these things for 30+ years, I've had to rebuild more installations from scratch which is a MAJOR pain on numerous levels.
When I started doing mission critical tasks that I needed the absolute minimum possibility of system failures, I switched to RAID 10. I've had a number of HDD failures and never lost a single thing, transaction, let alone complete system failures and have never had any subsequent down time.
- Don't scrimp on power supplies. Some studies show that as much as 90% of all (hardware) failures can be traced back to Power Supplies Buy good - high quality and try to keep peak loads below 75% max of your Power Supply capacity. 2/3 or even 1/2 is even better.
- Heat DESTROYS electronics. Cooling fans, including ones for HDD, are relatively VERY cheap compared to the cost of hardware failure due to overheating. All of my DeskTops have at least 16 fans in them. I also put heat sinks on EVERY IC but the smallest ones on both the MoBO and the cards. This includes ALL of the Voltage regulators. The latter are almost always 3 pin packages, though sometimes the ground connector is on the bottom of the IC and soldered to the ground plain of the MoBo to use it as a heat sink. Fit, bend and cut the black aluminum heat sinks carefully, and even end the cooling prongs / finger out more where possible. Put a little silicon heat sink compound carefully on the top of the IC then push the heat sink down onto it and twist it a bit to spread the heat sink compound around so that it covers the full contact area between them. Put a little blob of high temperature automotive silicon RTV rubber on either side of the heat sinks to hold them in place. Think this is ineffective? I've had CPU Voltage regulators get so hot that hey have un-soldered themselves and then re soldered in the wrong place shorting out because they got so hot.
On one card, they put to voltage regulators on the opposite sides of th PCB in the exact same spot. Great for board layout, but the worst possible heat design. Initially the chips got so hot that they would burn my finger tip on contact! )< 8( I put a heat sink on each one, in this case ones that had folded fingers/tabs that I bent out and spread out like spider legs sticking out all over the place. These 2 chips are now just barely warm to the touch. (< 8)
Have some tiny muffin fans from old CPUs? Glue them onto the heat sinks for the North and South Bridge controller chips. Put a couple of (120mm) muffin fans on the outside of the case blowing relatively cool air onto both the CPU and MoBo. If the general area of your DeskTops (mine sit on the floor under my desk) builds up to much heat then put an oscillating fan or two there helping to keep the general area cool.
Like most, I don't like the noise build up, so I use more, lower speed and quieter fans.
These cooling measures are all relatively inexpensive and well worth the time and effort.
If your HDD cooling fans seize up, especially the ones with bushings instead of ball bearings, and you catch them before they burn out; you can (clean and) re-lubricate them with some light oil. I just use 5W or 10W motor oil.