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15k RPM IDE Hard Drives?
OutRigged asks: "SCSI hard drives have had speeds in excess of 10,000RPM for years, yet IDE has always been stuck at 7200RPM. Is there some kind of technical reason IDE drives don't go above 7200RPM? I can't imagine cost being that big of an issue, and the connection is certainly not a problem, with Parallel ATA capable, at least theoretically, of speeds over 100MB, and Serial ATA capable of even more. With hard drives now reaching sizes in excess of 300GB, don't you think we need a speed increase?" If you are wondering what the terms "Parallel ATA" and "Serial ATA" refer to, check out this article.
SCSI drives are built to a much higher standard than IDE drives, especially the 10K RPM drives. Cost is a huge issue, especially when much faster spindle rates are concerned. Increase the rotational inertia and speed and you have to have a pretty fancy bearing system to cope with these loads. This sounds simple, and it is, but it is not cheap. The greater the rotational inertia a drive has, many aspects like passive cooling, fancy materials have to be considered vs the intended consumer of such a drive. Typically, SCSI drives are used by corporations that usually have a nice service contract attached to the hardware. In terms of IDE, which is the end-user and home market of such a device, coupled with the limitations of the IDE interface combined with Microsoft's problematic IO/IDE software, and we realize that going faster does nothing for anyone. Except for maybe driving up costs for everyone involved and curtailing the MTBF figures. If anyone will do it, WD will, what with its fluid bearings. But, we shall see =).
That's what iSCSI is for.
Initially it will run at arround 150Megabytes a second, however should be able to increase to 600.
AFAIK, the spinning mechanics of SCSI drives are the same as IDE ones, just that they are generally machined to a higher spec than the IDE ones. Another "let's give the common people something less durable, banking on that it won't be used as hard" thing.
Note the recent move to 1 year warrenties on IDE hard drives. SCSI drives are still 3-5 years. Honestly, I'm seriously thinking of doing SCSI in my next computer. Two years ago, I got a new computer and got ATA in it. It's been a good computer, but it's starting to feel it's age. My previous computer had scsi in it, and was a dual processor. The extra money I spent (almost 3k when I bought it) helped it last an extra year over theis one as far as speed was concerned.
If you do any serious disk activity, SCSI is a very very good way to go. If you plan on more than one person on a computer at a time, go scsi. For instance, I have a coworker who runs windows 2k at work and has Terminal Services running in admin mode. I logged in and started installed cygwin on it (we're testing cfengine on windows), and it hammered his machine. Made it unusable. That was just downloading stuff to disk! It's a p4 1.7 dell desktop job. My dual p3-700 with scsi never experienced anything like that until both processors were hammered running chemistry code and doing heavy disk activity.
I don't have any empirical data, I just have experienced too much IDE sub-standardness. You pay extra money for a reason, but I personally think it's money well spent.
-- Who is the bigger fool? The fool or the fool who follows him? --
HD's already have multiple heads - one for each platter. However, they can't all be used in parallel to get some sort of on-disk striping system because the heads need to individually fine-tune to the specific track they need to operate reliably.
:)
Since there's only one head assembly they're mounted on, tuning one head means the other heads get out of whack and become useless while the other's operating.
This requirement for precision means a multi-headed HD like that would need multiple head assemblies. Open up your favourite HD and see if you can work out where to put it
In short -- it's not worth it. You introduce more compexity (== cost == less demand) and things to go wrong, when you could just buy another drive and stripe and probably still come out cheaper and more reliable than a single two headed drive.
It'll probably be faster, too, since you've then got two interfaces to squeeze data down.
Gigabit Ethernet:
1000^3 bits/sec = 1,000,000,000 bits/sec
1,000,000,000 bits/sec / 8 = 125,000,000 bytes/sec
125,000,000 bytes/sec / 1024 = 122070.3125 Kilobytes/sec
122070.3125 Kilobytes/sec / 1024 = 119.20928955078125 Megabytes/sec
Fast Ethernet:
100,000,000 bits/sec / 8 = 12,500,000 bytes/sec
12,500,000 bytes/sec / 1024 = 12207.03125 Kilobytes/sec
= 11.920928955078125 Megabytes/sec
Bus bandwidth:
32-bit/33 Mhz PCI ---> 127.2 MB/sec
64-bit/33 Mhz PCI ---> 254.3 MB/sec
64-bit/66 Mhz PCI ---> 508.6 MB/sec
64-bit/133 MHz PCI-X ---> 1017.3 MB/sec
IDE Interface bandwidth:
Ultra ATA/33 ---> 33 MB/sec
Ultra ATA/66 ---> 66 MB/sec
Ultra ATA/100 ---> 100 MB/sec
Ultra ATA/133 ---> 133 MB/sec
Serial ATA 1.0 ---> 150 MB/sec
SCSI Interface bandwidth:
Wide ---> 10 MB/sec
Fast ---> 10 MB/sec
Fast Wide ---> 20 MB/sec
Ultra ---> 20 MB/sec
Wide Ultra ---> 40 MB/sec
Ultra2 ---> 40 MB/sec
Wide Ultra2 ---> 80 MB/sec
Ultra160 ---> 160 MB/sec
Ultra320 ---> 320 MB/sec
Single disk sequential transfer rates (STR):
SCSI Seagate X-15K.3 --> 76.4MB/s - 51.1MB/s
SCSI Seagate X-15 - 36 LP --> 60.5 MB/sec - 45 MB/sec
SCSI Seagate X-15 --> 41 MB/sec - 29 MB/sec
SCSI IBM Ultrastar 36LZX --> 34.8 MB/sec - 22.8 MB/sec
IDE IBM 60GXP --> 39 MB/sec - 21 MB/sec
IDE Western Digital Caviar WD1000JB --> 43.8 MB/s - 27.9 MB/sec
It's arguable. I've heard nightmare stories about high RPM SCSI drives' reliability. And, from a cost point of view, you could probably buy 4 20 GB IDE drives for the price of one 18GB 15k RPM drive and set them up in RAID-0+1 or -3 and have vastly better reliablity and speed.
Raid 3 is pretty atrocious unless you are reading and writing HUGE files all the time.
Raid 3 has synchronized disk heads, which means all drives will be reading the same stripe, or writing to the same stripe, at the same time.
For best performance with redundancy, Raid 10 (or 0 + 1) is by far the best choice. A Raid10 array gives you 2 different data paths for writing data (just like a 2disk raid0), but gives 4 locations for reading data back (like a 4disk raid0). Plus you still have the redundancy built in where if any single drive failed, no data loss. The downside is that 4 60gb drives will only give you 120gb of usuable space.
--
What is it with everyone typing "etc, etc" at the end of everything now? That is really annoying to read. On top of that, if you knew what "etc." was short for and meant, you would realize you don't need more than one. Typing more than one looks stupid and makes you look like an idiot.
If you want decent performance and staggeringly high reliabilty, try to find NOS (new old stock) server grade SCSI drives. The big 5-1/4" full height Seagate drives are built to last forever, and because they have an 'unfashionable' large form factor, you can get them on eBay for $30-50 each in 7-9 gig size. Stick 'em in the back room on an NFS server with a Fast Ethernet card and you've got your reliable storage solution.
Quiet cooling? That big wooden door between you and the big roaring box that contains the drives should suffice.
Maxtor Atlas 15k RPM SCSI drive
Maxtor DiamondMax 7200 RPM IDE drive
- Michael T. Babcock (Yes, I blog)