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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.
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? --
I've also seen in several benchmarks, the modern 7.2k ATA drives with 8mb cache in RAID configurations with a decent (or even Promise :) controller sometimes beat out 10k SCSI in the same RAID configurations. I'm sure this is also dependent on load patterns, driver/controller efficiency, etc, but it is something to chew on.
Personally, I've mostly stuck to 5400 rpm ATA in RAID for higher reliability. For storing large files with little random access, the rotational latency isn't really a big deal, so you can make up the difference in sequential speed by adding an extra drive or two.
That said, I did recently build an ad hoc NAS computer with 180GB 7200 RPM WD ATA drives, quantity 5, in software RAID5 for about 680GB usable. I used two ATA100 two port Promise controllers (with their own additional cache), and both onboard ATA channels for the RAID disks.
The root/OS disk and CDROM was some random smallish SCSI stuff we had laying around. This was to free up available ATA ports.
That thing flys. Compared to other 3ware ATA RAID5's we have with 5400GB Maxtor disks with 2MB cache, it pushes out a lot more per/disk throughput.
I'm kinda leery considering the promise cards have cache, and also the drives have large cache, none of which is battery backed directly, but this server is not being put into a critical role, and is kept on a UPS. I've noticed that battery-backed cache seems to have lost favor in RAID controllers. There is still a danger, correct?
One thing that is striking about it is the latency. It just "feels" fast. I think that may have something to do with using Linux software raid5d rather than 3ware hardware RAID, in addition to the cache and higher rotational speed.
I've had enough abrasive sigs. Kittens are cute and fuzzy.
It would reduce reliability, as most catestrophic failures of hard disks involve head crash of some sort. Twice as many moving parts is bad, mmmkkkay. :)
The head assembly also takes up quite a bit of room. You would probably have to go to a half height 5-1/4 form factor like old SCSI disks were.
I've had enough abrasive sigs. Kittens are cute and fuzzy.
It IS expense...so often we forget, but only recently were harddrive manufacturers having problems with their 7200RPM and in some cases even 5400RPM drives. The reason is heat. If you check around, you'll find that the largest 15000RPM drive is made by Seagate (it's ~80GB and it's ~$1000)...why???
When you raise the number of bits per inch of storage surface you create more stress and heat. When you raise the RPMs you create more heat (alot @15000RPM). The overall effect is that you can't use the cheap parts that are used in most IDE drives...every piece of the drive must be manufactured to the highest specifications. Motors have to be of the highest quality. Hydrodynamic bearings must be used instead of metal ball-bearings...this all increases the cost (as it pushes the technology).
The reason why these faster drives are not sold as IDE is simple. Anyone who is willing to pay $1000 for a ~80GB harddrive is also willing to pay $75 for a decent controller card (if it's not already built into their workstation).
How many ppl are going to be willing to pay $1000 for an 80GB IDE drive when they can buy a 300GB drive for 1/3 the cost? The end result is that most consumers simply don't care about the speed...the majority of IDE drives go into OEM systems and the consumer probably won't know if they put a 4500RPM drive in the system.
So, why not get the best of both worlds. Buy a 20GB 15000RPM SCSI and put your system files and most widely used apps on that (~$130 for a 18G Seagate). And then buy a larger IDE drive for archives.
When you think about it, you shouldn't need more than 20GB for your system, apps, and maybe a few games.
As far as the slower IDE drive, just spend your money on more RAM for the system and increase the cache. And don't rely on the CPU intensive built-in IDE controller on most Intel/AMD motherboards...buy a decent controller card instead.
And if you really want to get ~15000RPM with IDE technology, just get an IDE RAID controller and use striping...using this method you can actually get to much higher theoretical speeds than a single 15000RPM drive. with 4 7200RPM drives you could get up to a theoretical speed of 28800RPM!!!
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
maybe i should just start selling ceramic heaters in a regular hard drive profile, attach a 512mb compact flash card, and claim it's a half-gig 20,000 rpm drive. people'd probably believe me, too!
:)
moox. for a new generation.
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.
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Market forces drive IDE drives to be built as cheaply as possible while still having the right buzzwords to make consumers believe they're faster than their competitor. RPMs higher than 7200 still don't register with the mass populace, so it's not yet a factor.
SCSI hard drives are all about top-end performance. That's why some SCSI drives cost $1,500 for the same capacity as a $150 IDE drive. It's about being able to reliably move the platter at twice the speed of IDE, and having the correct drive logic and buffer memory to make it useful in the real world, getting very high MTBF numbers, etc..
Comparing typical IDE drives versus high-end SCSI (or FC for that matter) drives is like comparing small asian economy cars with the contenders in the F1 racing series. They have entirely different goals.
11*43+456^2