SAS hard drive

Can they be used in a desktop environment with an adapter?

One like this one: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=261093115470

Would 10,000 rpm make any noticeable speed increase on my desktop over 7200 rpm?

not got any SAS drives myself but

http://www.gettingolderandwiser.com/technology/how-to-add-hp-sff-sas-drives-to-your-desktop-pc.html

but id assume you could get a SAS card or sometihng and add them that way

Basically, no.

Both this generaton of SAS and SATA II are 300 mbps so the bus isn't going to go any faster for you. If you have to do a lot of non-contigious seeking on the disk (random access) then seek time can be reduced by the extra speed. For doing linear reads and writes on a defragmented drive, there is going to be some difference but not a vast amount of difference as the controller is at full speed anyway. Were you stepping up to 600 mbps or SSD the answer would be different totally.

So in summary: 10,000 or 15,000 RPM drives reduce seek time (waiting) for the disk head. They don't speed up the controller.

Yes they can be used in a desktop environment with the correct HBA, but as I said last time they aren't cheap and quality is everything with HBA's that are usually designed for RAID configurations. So going cheap isn't going to give good performance. We are talking about PCI-x or PCI-e card with their own CPU, removable RAM chips and dedicated on-card UPS here. So again; if you want a storage array, frankly you would get better bang for your American buck getting a SATA 6 controller and a SSD or a couple of SATA III drives.

SAS HBA's get around the bus width limit by using all that expensive caching and processing to really optimise how data is streamed onto the disk, so with the correct HBA performance will be better at 7200 RPM compated to SATA at 7200 RPM.
Applications where 10,000 rpm is beneficial obviously include databases. Instances where SAS is beneficial, servers, rendering and compiling.

The only other benefit that I can think of is that you can connect SATA drives to a SAS HBA, though you don't get all of the SAS goodness.

What did you decide to do?

Well I put them both on eBay. The 146GB drive sold pretty quick...the 36GB is still sitting out there...not much interest, even at ten bucks...

Ah. Are you going to play with a SATA storage array?

Nope, no reason to really...nothing much, if anything, to gain by it. Now if I had a dedicated hardware server to use them in...well that might be a different thing...but I'd really need a better internet connection anyways.

I can only upload at 300kbps while I have downloads of 30mbps...wonder why upload is so slow versus download....why is that for the normal home internet connection?

In the UK you often have the option of adjusting the ratio. We call the ISP and ask for an adjustment in the frequecy band allocation on the DSL. That decreases the download speed to increase the upload speed.

Usually low upload speed's are designed to stop you from serving... though 300kb on 30mb is shockingly poor and I suspect is actualyl preventing you from using the full 30mb at times!

I actually get better than 30mbps download speeds most of the time...normally around 38-45mbps...but my upload speed never goes much beyond 330kbps...

If you want to improve speed nothing beats an SSD, while a 10k rpm drive may be 5-15% faster, if that, in the real world, a good SSD can be several thousand percent faster. My computer used to be slow as molasses in January, even opening the Windows calculator could take 1-2 minutes. Over a year ago I replaced my C: hard drive (which was the fastest 7200 rpm drive on the market) with a 550 mb/sec SSD, even though on paper the drive is "only" 500% faster, in real world is closer to at least 10 000% faster. For example Windows calculator which took 1-2 minutes to load now appears instantly, Photoshop which took 5-15 minutes to load now fully loads in 4 seconds. I also copied an image of my old C: to the SSD, so it wasn't a clean install, it was a duplicate of my old slow drive.

The difference is absolutely mind boggling.

By the way just before installing the SSD I had upgraded from 2 to 8 GB of RAM, it made pretty much no difference whatsoever in speed, I took it out, returned it, installed the SSD and everything is at the very least 10 000% faster, even after months of having 100+ programs running without ever rebooting and with only 2 GB of RAM (Windows actually makes 6 GB of virtual memory on the SSD, but since the SSD is almost as fast as RAM it doesn't reduce performance whatsoever).

The reason for this is that by far the slowest part in a computer is the hard drive, and the system will only run as fast as the hard drive can read and write, so you can add all the RAM in the world and the fastest processor ever invented but if you're still running from a mechanical hard drive it's going to be slow as molasses (compared to an SSD at least).

Imagine you have a pipe going from point A to point B, the pipe starts at 6" diameter, then narrows down to 5 inches, then to 1/4 inch, then back to 6". If you want to increase the flow of water are you going replace the 5" section (faster RAM, which would do no difference as there is a 1/4" section just after), or are you going to replace the 1/4" pipe (the hard drive) with a 4" pipe (an SSD)?


Edited by aab 2012-09-08 2:44 AM

AAB, something was wrong with your hard drive before. I believe it must have been failing. That would have driven me nuts! Even my original 8086 was faster than that.

My Windows calculator opens in less than a second...Photoshop loads in a couple of seconds also. I'm running a standard SATA 7200 rpm drive. As a matter of fact, everything open and runs just fine...no lags whatsoever.

As far as your Venturi analogy...my bottleneck isn't in my computer...it is a limitation that is inherent in my ISP. They limit the data upload speed unless you are a commercial "business" customer to 300kbps.

My questions were more inquisitive and theoretical than anything...I am unfamiliar with the practical aspects of SAS drives, though I do understand the theory behind them.

Lets not get too carried away here, I think the fastest SSD is about 700 MB/s over 1 channel and DDR3 is about 6400 MB/s over 3 channels or (more recently) 2 channels.

RAM doesn't increase the speed of your computer, anyone who tells you that it blindly does doesn't know what they're talking about. RAM prevents you from having to page data from RAM onto disk, which prevents you from having to wait for it to be swapped in and out and from having RAM related paging operations from holding up time on the hard drive sub-system.

When you get to a certain ammount of RAM, you seldom need to page the disk, so performance increases.

Under Windows Vista + additional RAM is also used to prevent data from having to be read from the hard disk system in the first place. The much complained about SuperFetch service copies data from the disk into RAM at boot. When the information is needed it is read from RAM and never from the disk, increasing performance. The more RAM you have the more DLL's and exe's you can store in RAM, thus improving performance (after a hit for a few minutes at first boot). SuperFetch does have it's imposed limits though for client OS's.

Most client system performance problems are with the disk controller. So you are right about bandwidth. In my experience though, disk controller chipsets seem to degrade with time, so if you have a slow PC, even getting a cheap VIA plug-in controller can make a massive difference.

You may have forgotten the part that Windows makes a 6 GB page file since I normally have 100 or more running programs, that's why it was so slow from a hard drive. If course if I only ran 10 programs it was fast, but I never do that.

Also, even with all the RAM in the world, loading a file from the hard drive will only ever go as fast as the hard drive can.

I don't understand how your internet speed affects your computer speed, unless you're referring to internet download speed. Local computer operations will go at the same speed regardless of internet connection speed of course.

I know on paper ram is a few times faster than the fastest SSD, but as I said due to the fact I have only 2 GB RAM and run over 100 programs at once, Windows makes a 6 GB page file so 75% of my "RAM" is on the SSD, and even so it's literally as fast as if it was from RAM, never the least bit of delay whatsoever.

For example with a hard drive, maximizing a window that had been minimized for a few days could take several minutes as it gathered the data from the page file to redraw that window. Now, even with as little RAM and as many running programs, even maximizing a window that's been minimized for weeks is instant. Remember, the one and only thing that changed is the C: drive went from being a mechanical hard drive to a 550MB/Sec SSD, it's even an exact image copy of the slow drive that's on the SSD, so you can't say the speed is due to a clean install, it's not a clean install.

The reason "real world" speed with SSDs is dramatically faster than hard drives (MUCH more so than "on paper" specs would lead you to believe) is that the transfer rates on the "on paper" specs of hard drives and SSDs don't take into consideration the often dramatic slow downs the seek time of a mechanical hard drive has to deal with. If your data is spread al over the drive in a mess, you're not going to get anywhere near the claimed transfer rate. On an SSD, you do get the claimed transfer rate at all times as long as your computer can handle it, and it's this almost instant seek time of SSDs that cause them to be literally 100 times faster in many circumstances even though the transfer rate on paper is only 5 times faster than my old hard drive.

You're right that RAM doesn't make your computer faster but that's an assumption many people have which is completely false in most cases.

You also have to consider that one way or another files need to be read from the drive and it will never go faster than the drive can go, so for things like loading, copying or moving large files an SSD will make a huge difference while more RAM wouldn't help those go any faster.


Edited by aab 2012-09-09 12:28 AM

literally perceptively

The fact that you are running a 6GB page file against 2GB memory is slightly concerning as it is generally considered that it should be 1.5 times the amount of RAM. Your processor must spend a lot of time dealing with hard faults (another performance hit). It is no wonder you were seeing applciation load-back times in the tens of seconds if you had to swap data in and out on that scale.

Sounds to me like you do actually need more RAM. Think of the unnecessary wear you're putting on the SSD