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Areal Density, Solid State Lies and Bull**** Benchmarks.

Ok, so here's another rant, regarding Solid State Storage, Raptor RAID and SCSI RAID as my examples.

Gigabyte iRAM v0.98 on ICHR7 Sata

Burst Speed: 135.8 MB/s
Average Read: 130.6 MB/s
Random Access: 0.0 ms

Raid 0 (74GB) Dual WD Raptors 36GB 10,000 RPM on Marvell 61xx RAID Controller

Burst Speed: 171.8 MB/s
Average Read: 75.1 MB/s
Random Access: 9.0 ms

Raid 5 (500.1GB) 3x WD Sata 250GB 7200RPM on ICHR7 RAID

Burst Speed: 2026.9 MB/s
Average Read: 106.1 MB/s
Random Access: 13.0 ms

Raid 5 (90GB) 6x 18GB SCSI 10,000 RPM Drives on ServeRaid 4Lx PCI-X Card (Netfinity)
/dev/sda:
Timing cached reads: 608 MB in 2.01 seconds = 302.49 MB/sec
Timing buffered disk reads: 70 MB in 3.00 seconds = 23.33 MB/sec

Now you might look at these and think they are unfair, they are. I'm going to comment a little bit on each one to give you a decent background on what I'm talking about.

First off, Let's talk about how come the ServeRAID card is so much slower than any of the other items on this list. If you know a little bit about areal density, you probably know the answer already, if not, I'll fill you in.

The concept of Areal Density is quite simple. It is simply the amount of bits you can pack onto a medium. For example current hard drives have areal densities of several gigabits per square inch.

Now you take a look at those SCSI drives in that Netfinity, you'll notice they are 18GB SCSI drives. That's rather old, and the way they were marketted, 9GB, 18GB, 36GB, gives you an idea of the areal density per side. We'll use Gigabytes to explain this one to make it a bit easier. Remember that all of these drives are the standard 1" kind.

You have a SCSI 9 GB Hard Drive, it has a single platter, which uses a single side to store 9GB. Our Easy Areal Density is 9GB per side per platter. So we have a read speed of approximately 9GB per platter.

If you take a SCSI 18GB Hard Drive, it has a single platter, which uses both sides to store 18GB. Our Easy Areal Density is 9GB per side per platter. We now know a 9GB SCSI drive, should perform roughly the same ignoring all other types of optimizations.

If you take a SCSI 36GB Hard Drive, it has two platters, which uses both sides to store 36GB. Our Easy Areal Density is still 9GB per side per platter. We have no performance increase.

Now you take a Western Digital Raptor 36GB SATA drive. It has one platter, and uses a single side. Our Easy Areal Density is 36GB per side per platter. Ignoring all other features and assuming the components are identical, we now have a 4x increase in data stored and read in the same head movement as one of the SCSI drives mentioned earlier. That would theoretically translate into 4x faster read times or 93.82MB a second. Now, we know that the drives aren't getting that, from the benchmarks above, and the fact that I haven't seen a single hard drive run at that kind of pace. This does give you a clear idea of how read speeds from a newer modern hard drive can vastly outpace a drive from 2 or 3 generations ago, ignoring all the other technological innovations that are used to increase their throughput.

Now, I know what you're saying, I'm comparing a Raid 0 Raptor array to an old Raid 5 SCSI array, and I am. Its just for illustrative purposes. Benchmarks lie, plain and simple. The only way to accurately gauge a system's performance is to use that system for an extended period of time. You can yadder on to me all day about 200 fps in FEAR, but after 70 FPS (For those with awesome eyes,) its all just wasted potential.

Now lets get to my main rant for all of this. Solid State Storage vs Mechanical Storage

I'm sure there are lots of you out there that got a hard on for the iRAM when it came out. Its specs are impressive, its size isn't all that great, but compared to the competition, its affordable. While some of the things people say about it are true, some are not.

The Pros:
General Windows Performance is increased. (See faster all around access.)
Boot times are increased (Except your BIOS screens.)
Faster all around access (By a factor so small, you'll only notice it doing larger operations.)
Free Backup Utlity (How nice to complement the ****ty battery.)

The Cons:
The Battery (I don't know where they bought them, but they sure as hell aren't reliable. Mine lasted 3 months before going completely kaput. Its not worth mailing the bloody thing back for a replacement either.)

The Cost (While its cheap compared to other options, 4 GB of RAM is going to cost you a hefty bundle, ~ $148.35 per GB at the time of this writing, that's quite hefty when you compare it to a couple of Raptors in RAID 0. Its about as safe as the iRAM anyways, and 300 GB of storage for the same price, not to mention the ~$200 for the iRAM itself.

Compatibility (My testing of the iRAM has found quite a few glitches. It now works with Linux finally, after being on the market for almost two years. It has problems with Gigabyte Boards, at least the ICHR8 chipset. It doesn't take double sided RAM, so you are out of luck if you bought a bunch of that **** off Ebay hoping it would be alright. Most system boards I've tested it with don't like to boot with it properly. Generally you can't boot from it in SATA mode and have to switch to RAID mode for it to actually boot. It shows in all the menus fine, just does not load the MBR.)

The Complete BS:

3 Second Windows Boot Time. (I don't know where the **** they got this number, except from right in their ass, because there is no god damned way a Windows box is EVER going to boot in 3 seconds unless you strip all the drivers out of it. The delay isn't just hard drive access, but driver polling, detected, services starting up, etc.

Install Windows in Seconds. (Simply not possible, unless you install iRAM to iRAM. CD Media can't even touch Hard Drive transfer speeds. The install is just as speedy as any hard drive out there, you might save a minute, tops)

50,000 Times faster. (Where they got this idea from on the box, I have no idea. 150 MB/s max theoretical throughput isn't near this, and neither is 0.0 ms latency time. There is still a latency sure, but the only time latency counts much is in IOs per second, and if you decide to run an iRAM on a production server, I sure hope you aren't hosting anything important or large.




To put it simply, Solid State is nice. It increases speed, and where IOs count, its a big plus. However for the consumer, its not going to give the gains it promises. In the end, you're going to spend around $1000 to get a 4GB Hard Drive. I think I'd rather have 3 Raptor 150GB drives in Raid 5. Sure the Latency will be higher, but you'll actually have redundancy, and you can buy a shiny new hardware Raid card with the extra money.

Lastly, lets mention the lovely burst time above for my RAID 5 Array: Burst Speed: 2026.9 MB/s
I used HDParm for that test, using the full 32mb buffer, and I just wanted to point out that I have two drives on SATA 2, and 1 drive on an IDE to SATA 1 adapter in that array. That means we have a theoretical max throughput form the buffers of 750 MB/s. I don't know how the hell it got 2026.9 MB/s out of that. It's simply not possible. Also, the read speed, Average Read: 106.1 MB/s is ludicrous. I never get that kind of transfer rate, even to the iRAM. It simply does not happen in the real world.

The motto of this story? Benchmarks are Bull****.

Dan

Written by Dan on 2015-01-22 18:25:18

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