Hi!
I Always wondered what the mission was for raid. And How it affects dedicated servers. Like, How would it make my decision better between a dedicated server With raid or with out.
Sorry for the stupid question.

If you run a webhosting company, and per chance, one of your Hard Drives would Crash.
Wouldnt you be completedly Screwed?
Lose all Data, Unhappy Customers... Screwed.

If you use Raid1, You can Mirror 2 IDE HD's
If one Crashes, everything on it is copied to the other HD,
and i dont think you suffer one minute of downtime.

Its a security measure, just in case.

I'm not sure how many ppl actually use this?
I'd be curious to find out though

The keyword in RAID is the R...Redundant.
Everything that gets written to one disk gets immediately written to the other disk(s).
We use RAID1 with IDE, and it helps me sleep better at night.

Is raid a part?or software?

Really, it's more of a philosophy. Kinda like asking 'what seperates 4 9's (99.99) from 5 9's (99.999)?' when talking about uptime. Good RAID is not just software -- and it's not just a part you pop in and then expect it to take care of everything. Like anything that's advanced with computers, you really need to do a lot of reading to understand it.

Check out:
http://www.acnc.com/04_01_00.html
for a VERY nice in-depth site about different RAID levels.

and check out
http://linas.org/linux/raid.html
for some great resources and research for using RAID on Linux.

Dan

Originally posted by creid
Is raid a part?or software? Both, sort of. Or, sort of neither. :)

RAID stands for Redundant Array of Inexpensive Disks. There are different types, or "levels" of RAID, as AceCharge explained one of those is RAID Level One, or mirroring. RAID 5 is also worth considering for a webhosting environment. The choices of which level of RAID to use in a specific application depend on balancing speed, data "recoverability," and cost.

There are both hardware and software approaches to implementing RAID, and solutions now available for both SCSI and IDE hard drives.

I had a couple of links to good explanatory pages, but I can't find them now... try here, though:

http://www.webopedia.com/TERM/R/RAID.html

Thanks guys! I got the idea of raid 1. :D

Is Raid neccesary?

Originally posted by creid
Is Raid neccesary? Necessary? Assuming you're talking about for a web server application, generally no, it's not necessary. On the other hand, there are very clear advantages in reliability, redundancy, and speed when using a properly installed RAID subsystem.

It's not necessary, but for some applications it is absolutely essential. There are some uses for which it'd be overkill, but there are some for which you'd have to be crazy not to use it.

Originally posted by JayC

It's not necessary, but for some applications it is absolutely essential. There are some uses for which it'd be overkill, but there are some for which you'd have to be crazy not to use it.

Got any examples?

RAID can be software or hardware. The hardware RAID controllers are around $600 ish while software will run you about 1/8th or 1/10 of that.

We use hardware RAID5 with multiple SCSI disks. For example three 36 gig disks in raid5 will give you 72gig of usable space that you can have mounted on /var, /usr, /home, and so on.

The way it works is if a drive fails you can pull it right, throw it away :) , and drop in a new drive. The controller using the two other drives will replace the data you had across the third drive. Sort of an x+y=z type of thing. Pull any one of those out and you can always still determine what is missing.

a good example of raid is where I am contracted to currently, we have a HUGE amount of disk storage, many hundreds of GB's

to store that amount, imagine having 20 disks, all containing the data, as follows:

1) - - - - - - - - - - - - - - - - - - - -

ok, now imagine one of those disks fails, what happens? the whole thing goes down and you have to recover 600GB of data. that is an example without raid, now imagine the example with raid:

1) - - - - - - - - - - - - - - - - - - - -
2) - - - - - - - - - - - - - - - - - - - -

ok, now imagine if one of the above disks fails on row 1, the IDENTICAL disk on row 2 will take over giving you time to go to your server, providing its a hot plugable server you can pull out the failed disk on row 1 and replace it, the mirror is then rebuilt.

where i work we have over 400 hard disks serving files, i think we have at least 1 failure EVERY DAY

Does the morrior rebuild it self?

Originally posted by creid
Does the morrior rebuild it self?

Yes

Originally posted by Jag
RAID can be software or hardware. The hardware RAID controllers are around $600 ish while software will run you about 1/8th or 1/10 of that.

We use hardware RAID5 with multiple SCSI disks. For example three 36 gig disks in raid5 will give you 72gig of usable space that you can have mounted on /var, /usr, /home, and so on.

The way it works is if a drive fails you can pull it right, throw it away :) , and drop in a new drive. The controller using the two other drives will replace the data you had across the third drive. Sort of an x+y=z type of thing. Pull any one of those out and you can always still determine what is missing.

Very true on pricing but I have had problems in the past with software raid's. I would stick to hardware only.

Ok
So I think I get the concept. So if I were to build a server tosaid with Raid1 on the server. How would I come about doing this?

Chris

Just get a RAID capable build-in motherboard. It'll comes along with drivers and instructions which normally only support level 0 and 1.

Any Reccomendations of such motherboards?

Originally posted by xtstrike
a good example of raid is where I am contracted to currently, we have a HUGE amount of disk storage, many hundreds of GB's

where i work we have over 400 hard disks serving files, i think we have at least 1 failure EVERY DAY

XTSTRIKE, your have a HUGH failure rate, would you mind advising us on what hard drives your using. if on average anybody here was to have a drive going down every few days the losses would be hell. ( at least 1000 per month easy )

I'm guessing here but with such a high failure rate are the drives the type where they all are in alignment with eachother ( where the spindle on each drive is in the exact order to the other 400 drives for faster reads and writes ).

Also one other question... 4 or 16 tera-bytes server. It must have been a hell of a time to optimize those baby's. by optimizing your raid, you can define the I/O chunk into 2K, 8k and other size blocks, this can help in the read time a lot. I'm not sure what the rules are for this. ... sorry

for more raid info go here, just about every type of raid is mentioned.
http://www.acnc.com/04_01_00.html


-Michael

Originally posted by creid
Any Reccomendations of such motherboards?

Presuming it's P3 series MB, some of the good models I've heard of are...

Abit VP6 (Dual CPU, Raid) Budget quality stuff.

MSI EP6337-815 (Raid) This good, what I'm using right now.

sqposter, I couldnt be sure of the exact replacement rate of drives but they are 18/32GB Compaq Hot Pluggable SCSI

they have a couple of thousand users, maybe more, some are fairly intensive users, they are in use 24 hours a day over 3 shifts

Im involved in database operations and the compaq support team are involved in server maintenance.

Ill get them to re-confirm their replacement rate of drives...

Originally posted by xtstrike
Ill get them to re-confirm their replacement rate of drives... It seems pretty high, because if you have 400 drives with one failing every day.... 365 drives out of 400 failing means the average drive fails in about a year!

Originally posted by xtstrike
sqposter, I couldnt be sure of the exact replacement rate of drives but they are 18/32GB Compaq Hot Pluggable SCSI

they have a couple of thousand users, maybe more, some are fairly intensive users, they are in use 24 hours a day over 3 shifts

Im involved in database operations and the compaq support team are involved in server maintenance.
Ill get them to re-confirm their replacement rate of drives...

Gee that real weird 18gb or 32gb series are real old work horse, if I recall correctly ( unless they are those 10000 rpm then I dont know )

but please tell us the make and model and lifetime. I've yet to kill a drive and I power up the same at least every day for the past 3 years ( my trading computer so it's active getting quotes all the time )

-Michael