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What is RAID and what does it do?

raid 0 provides improved performance (read and write) gains by splitting the volume and its data between each the member disks. the gains are achieved by having multiple disks working together for a read or write task at the same time instead of just one disk. this gain comes at a risk: an individual disk failure will mean an unrecoverable loss of the entire array.

raid 1 provides protection against an individual disk failure by having synchronized copies of data among two or more disks. read performance can also be increased. this comes at the cost of capacity, as each disk mirroring is mirroring each other instead of holding more data. a server can have a hot-spare and immediately begin rebuilding a degraded RAID-1 mirror upon disk failure. the main advantage is uptime and of course the ability to sustain a disk failure without loss of data.
 
I'm glad you made this thread T_Yamamoto because I'm basically in the same boat. I've heard a lot and read a little. I'm really interested in trying it out (at least, mirroring to start with).

I'm curious as to how it works when a drive fails and you swap it out. How does the new drive go from empty to fully mirrored so to speak? What level of risk is there in terms of a RAID controller failing and screwing up the whole array regardless of which type of RAID you use?
 
well 1. use a real raid controller.
2. never lose power or crash
3. raid is a burden we have to live with in business, it's not something anyone enjoys or brags about.

the only thing i've seen consumer raid is good for is raid-0 - and of course you have backups. raid-1/5 on consumer soft-raid is just too unstable in windows. it will let you down eventually.
 
zCypher said:
I'm glad you made this thread T_Yamamoto because I'm basically in the same boat. I've heard a lot and read a little. I'm really interested in trying it out (at least, mirroring to start with).

I'm curious as to how it works when a drive fails and you swap it out. How does the new drive go from empty to fully mirrored so to speak? What level of risk is there in terms of a RAID controller failing and screwing up the whole array regardless of which type of RAID you use?
Click to expand...

the recovery method is dependent on which raid controller (or softraid) is used. basically the process is remove old disk, put in new blank disk, and the surviving member of the mirror then synchronizes (copies) data to the new blank disk.

mechanical hard disk drives are MUCH more prone to failure than a RAID controller with no moving parts (barring a cooling fan)
 
With the exception that RAID-0 has no redundancy at all. I do consider it anti-redundant.

RAID is not a backup method.
 
corkyg said:
Just in case no one else does it, RAID= Redundant Array of Inexpensive/Independent Drives/Disks. I'm suprised you just didn't Google it. It's been around a l-o-o-ng time.

http://en.wikipedia.org/wiki/RAID
Click to expand...

This "inexpensive" crap in RAID definition has always bothered me and I strongly feel it is incorrect.

Really, a relative price factor in RAID definition? I don't think so.

RAID originated so many years ago, when single HDDs cost thousands of dollars and in fact were very expensive.
 
Emulex said:
well 1. use a real raid controller.
Click to expand...
Dunno, I had good experience with software raid and apart from the write hole with some variants which make a hw cache a necessity for acceptable performance I don't really see many reasons for one. It's not as if CPU power was especially scarce these days - at least for consumers with some small RAID of a few TB.
 
Emulex said:
well 1. use a real raid controller.
Click to expand...

Or a good software RAID implementation like mdadm in Linux or ZFS.

Emulex said:
2. never lose power or crash
Click to expand...

Never is hard to attain, but a UPS is definitely recommended.

Emulex said:
3. raid is a burden we have to live with in business, it's not something anyone enjoys or brags about.
Click to expand...

I wouldn't call it a burden and I definitely enjoy it when a drive dies and the server keeps running.

Emulex said:
the only thing i've seen consumer raid is good for is raid-0 - and of course you have backups. raid-1/5 on consumer soft-raid is just too unstable in windows. it will let you down eventually.
Click to expand...

Key phrase being "in windows", most of the other software RAID implementations out there are on par with the enterprise level controllers or better and always more flexible.
 
bigi said:
This "inexpensive" crap in RAID definition has always bothered me and I strongly feel it is incorrect. Really, a relative price factor in RAID definition? I don't think so. RAID originated so many years ago, when single HDDs cost thousands of dollars and in fact were very expensive.
Click to expand...


And, that is why it was changed. Today, it does not say "inexpensive." That was placed for historical purposes, because that is what it was originally. A / between two words means "either or." Choose your own poison. LOL
 
Emulex said:
1. use a real raid controller.
Click to expand...
Dedicated computing power and cache does benefit the RAID modes that do compute checksums, but not the trivial 0 and 1.


RAID is convenience. I've replaced 8 out of 10 disks from a server without a need to power down the server or restore from backup. The server does have a hardware controller and hotswap HDD bays though.
 
mv2devnull said:
Dedicated computing power and cache does benefit the RAID modes that do compute checksums, but not the trivial 0 and 1.


RAID is convenience. I've replaced 8 out of 10 disks from a server without a need to power down the server or restore from backup. The server does have a hardware controller and hotswap HDD bays though.
Click to expand...

i have suffered two drive failures so far, and thankful im running all raid 1 mirrors on my fileserver. i should get some more drives so i can have some spares handy instead of waiting for RMA.
 
T_Yamamoto said:
so RAID isnt for the average consumer?

more for servers and such?
Click to expand...

That was the original intent, yes. It was supposed to be for servers that needed to be highly available so that you could keep them running when a drive dies and while you wait on the replacement.

Later, RAID0 became a thing for gamers to use in their ricer PCs to speed them up more at the risk of losing the entire array when a drive dies.

At my house my data drive is a mirror simply because drives die way too often these days.
 
RAID 0 SSDs makes you happy. See that 5 GB file on the desktop? Right click, copy here, hey was there supposed to be a progress bar?

Drive dies? Start a reimage, take a piss, come back to a Windows login screen.
 
exdeath said:
RAID 0 SSDs makes you happy. See that 5 GB file on the desktop? Right click, copy here, hey was there supposed to be a progress bar?

Drive dies? Start a reimage, take a piss, come back to a Windows login screen.
Click to expand...

Provided you image often enough and even if you do it weekly you'll still have to resetup shit and wonder what other stuff is missing.
 
Not to start a debate, but I find it hard to believe that ANY software RAID will match the throughput/performance of an "expensive" dedicated controller. I haven't implemented ZFS or other soft-RAID solutions (Windows has in fact sucked) and I would be interested in seeing some benchmarks that show it will keep up with a high-end controller.
 
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