Opinions on raid option and whether worth while

[SoCalled]

Ok building a new rig (read specing it and getting our sysop to build it), and one of the options is for a raid motherboard. Apparently this means we can throw in four hard disks and mirror and what not. (Still reading up on this).

The rig will be used mainly for web site design, PSP, Photoshop etc. Would a raid design be way over the top for this, as will be a workstation.

Basically have a budget and can either go with the raid thing, or switch the bucks into something else.

And yes Justin will have top of range vid card, and a 2k+ monitor.

[JungleMan]

$2000 monitor?

How much is that in USD?

Anyways, as for RAID, SOME motherboards can use the controllers to double as extra IDE controllers. Check with me or others before choosing a board. Usually they aren't much more anyway, so always good to have the option of adding in more than 4 IDE devices.

If you are doing something mission-critical you will NOT want RAID 0, you should get RAID 1. If you want speed, get RAID 0. If you want the best of both worlds get RAID 0+1, which requires 4 identical disks and supplies speed and backup.

Most boards can do 0, 1, and 0+1, but some can't, so check first...

That said, I think it's pretty much a waste for your machine. Get a WD with 8MB cache and you should be set...

Oh BTW, wait a little bit and wait for the Radeon 9700, it is going to be awesome...

[SoCalled]

Without checking current exchange rates, approx $1200 US, 21 inch monitor.... cool.

Will get the Radeon card, have the 8500 in this rig l think and that is pretty impressive.

Thought the raid option was a bit over the top for a work station. Will chuck the cash into hard disk space l think. Dual 120gig hard disks, unfort only IBM available, usally go Western Digital or Maxtor.

BTW have put nxsupport back up to our HR ppl for re-evaluation, work related sites my ass, mentioned it has hardware forums and software evaluation forums, so fingers crossed.

[JungleMan]

Originally posted by SoCalled
Without checking current exchange rates, approx $1200 US, 21 inch monitor.... cool.

Will get the Radeon card, have the 8500 in this rig l think and that is pretty impressive.

Thought the raid option was a bit over the top for a work station. Will chuck the cash into hard disk space l think. Dual 120gig hard disks, unfort only IBM available, usally go Western Digital or Maxtor.

BTW have put nxsupport back up to our HR ppl for re-evaluation, work related sites my ass, mentioned it has hardware forums and software evaluation forums, so fingers crossed.

Even that is a LOT of cash for a 21 inch...

Ack, do whatever you can to avoid IBM hard disks, they absolutely suck! So many of them have died

Cool, if you want, I can move the Gen Discussion down to the bottom.

[SoCalled]

Naw she's right. After a little accident with a certain department's email access they are seeing the light somewhat. Am still trying to track down who showed those retards how to block internet access...

on the IBM HD front. May have to go the scsi option, and get some Maxtors instead....

[parksie]

The wonders of a secure shell and X forwarding

Most people running any kind of real server will tell you to use SCSI (lots of devices, good speed), but IDE should suffice for this.

I don't know why people had problems with IBM disks...mine's been perfect for years now.

PS: The disk of mine that *did* die was a Maxtor......

[Guv]

RAID 0 is not a good idea for most PC users. I will not discuss other RAID variations, which are not available on any standard PC.

RAID 0 provides twice the transfer rate once it gets started, or 3/4 times the rate if more than two disks can be used in the array. It gives the appearance of one large drive with twice (or 3/4 times) the transfer rate. It does this by what is called data striping.

In an array with two disks, even addresses are on one disk and odd addresses on the other. If 6 blocks (allocation units) of data were to be written, an I/O order for blocks 1, 3, & 5 would be initiated for the first disk, and a concurrent I/O order for blocks 2, 4, & 6 would be initiated for the other disk.

One problem is that you get double the latency time and usually double the head movement time with a 2-Disk array (3/4 times with a 3/4-Disk array). Latency time averages ½ a revolution, during which time half a track of data could be written or read.

Consider writing a track full of data.

• RAID 0 with 2 disks: Average latency is one revolution (½ rev for each disk). Due to the data transfers being concurrent, the transfer time could be as low as ½ revolution, but this is best the best case (It only happens if the data transfers are exactly synchronized, beginning and ending at the same time).
  
• Ordinary disks: Average latency is ½ rev, followed by one revolution to write a track of data.

With average latency, the RAID system requires a minimum of 1.5 revolutions to transfer a track of data, which is the average for the ordinary 2-disk system. Head movement is likely to be required on both disks, making the RAID system worse assuming average latency. Note that head movement is mechanical and is measured in milliseconds, perhaps equivalent to a quarter revolution or more.

The above shows that for a transfer of one track of data, the RAID system is slower. For less than a track of data, the RAID system is even worse. For somewhere between 1.5 and 2 tracks of data, the RAID system breaks even, and beyond 1.5 to 2 tracks it is faster. Typical PC applications do not transfer two or more tracks of data in one I/O order.

Hence a RAID system is a good idea if you typically transfer a lot of data with each I/O operation. This is not the case for most users.

BTW: I am not sure whether or not special software is required to request I/O orders for huge data transfers.

There are other problems with RAID 0.

• Head movement causes more wear & tear on a disk than anything else. Each RAID I/O tends to require head movement on two or more disks. This decreases the mean time to failure of some disk.
  
• If either disk in a 2-disk RAID array fails, data recovery is a nightmare. The remaining disk has every other allocation unit of a file. RAID is risky for a typical user unless there are frequent backups of the data.
  
• Fragmentation slows RAID 0 down drastically due to the extra latency. To avoid this, frequent defragging is required.

If you take into account the requirement for more backups and more frequent defragging, some of the gain in speed is given back on a system that gains from RAID 0. If your applications are not suitable for RAID 0, the defrag problem will result in a really slow system.

My system has three disks.

• OS & major applications are on the first disk.
  
• All data files are on the second disk.
  
• The OS Swap file and backups are on the third disk.
  
• Some partitions on all three disks hold copies of CD applications which run without the CD reader.

My system supports RAID 0, but I prefer the above organization, which minimizes head movement. The time saved due to less head movement can only be noticed by a sophisticated bench mark program, which might not even be a good model of what I usually do. However, I have less wear and tear due to less head movement, and I have images of my critical partitions. If anything goes wrong, I can easily restore my system by copying the backup images.

Unless you have applications which transfer large amounts of data with each I/O operation, RAID 0 is a bad idea. It results in slower Disk I/O for a typical user, and has potential for disaster if a disk fails. Furthermore, it increases the probability of disk failure.

With a 2-Disk system, a typical user is likely to get more I/O efficiency by separating the data from the OS & applications than by using a 2-Disk RAID array. On a 2-Disk system, I am not sure where the OS swap file should be: With OS & applications or with Data files?

BTW: Some systems have synchronized disks, allowing RAID 0 to avoid extra latency.

[SoCalled]

Thanks for that Guv. Sort of explains it all. Probably bypass the raid option by the sound of things. As stated is a workstation and not a mission critical server.

Cheers.

[JoshT]

Also, low-end IDE "RAID" controllers are BIOS-assisted software (or so I've been told). A good OS should be able to do software RAID on a normal IDE controller, I think. I've only actually tried Windows 2000 Server software RAID on non-system SCSI drives, though.

[SoCalled]

The OS of choice will be Win2k Pro. Solid and easy to tweak to what you want.

Apps will be PSP, PhotoShop, etc so maxing the ram will be required...

[parksie]

PS: As regards 2K's stability....badmouth NT/2000 all you want, I've only ever had a problem with them on hardware that was a) not on the HCL, and b) was only an initial-revision anyway

The NT box on my desk at work has been up, what, 80 days now? And that's how long it's been sitting there Come to think of it, I've only ever logged in once


RAID.....I have a HighPoint RAID controller on my motherboard (hardware) but I only use it for the ATA-133 interface

[JungleMan]

Originally posted by Guv
I will not discuss other RAID variations, which are not available on any standard PC.

RAID 1 (mirroring) can be used on most Highpoint/Promise RAID controllers, just that it's not very popular. I've only seen it used once in the threads I've come across at other spots.

Also RAID 0+1, but that's kinda what you are trying to avoid

Jello don't worry about RAID 0. Get yerself a couple of 120 gig Western Digitals with the 8MB of cache and be happy. Can you requiest this rig without a hard drive or OS, because I really would avoid IBMs like the plague.

[SoCalled]

Nope.

Parksie, Win2k is like my favourite OS at the moment after fecking around with Unix all morning and using the kill -9 to try and finish a process which was halting operations. Finally bit the bullet and rebooted.... stoopid unix...

[JungleMan]

Win2K is my favorite OS hands down. It's great on my Athlon but I'm also running it on my 500Mhz Celeron and it's smooth as butter, much faster than the 350 P2 and the 475 K6-2 (both which use a 100Mhz bus and this one only has a 66Mhz bus) which are running XP, those machines aren't mine