What is RAID and what does it do?

[T_Yamamoto]

Title says all
Ive seen people talk about RAID and such

RAID 1?
RAID 0?
what is all this RAID stuff?!

 

[Spikesoldier]

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.

 

[zCypher]

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?

 

[Emulex]

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.

 

[Spikesoldier]

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?

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)

 

[corkyg]

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

 

[mv2devnull]

With the exception that RAID-0 has no redundancy at all. I do consider it anti-redundant.

RAID is not a backup method.

 

[bigi]

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

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.

 

[Voo]

well 1. use a real raid controller.

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.

 

[Nothinman]

well 1. use a real raid controller.

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

2. never lose power or crash

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

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

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

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.

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.

 

[Old Hippie]

I really like this Visualize Your RAID site to explain the basics of how RAID works.

Sometimes pictures are worth a thousand words.

 

[corkyg]

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.

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

 

[mv2devnull]

1. use a real raid controller.

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.

 

[Spikesoldier]

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.

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]

so RAID isnt for the average consumer?

more for servers and such?

 

[Nothinman]

so RAID isnt for the average consumer?

more for servers and such?

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.

 

[T_Yamamoto]

okay. i see
so it isnt worth the cost (in a gaming pc)?

 

[exdeath]

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.

 

[Nothinman]

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.

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.

 

[zCypher]

If you're mirroring, are there still performance benefits?

 

[Voo]

If you're mirroring, are there still performance benefits?

Read yes (for larger reads at least), write no.

 

[Nothinman]

If you're mirroring, are there still performance benefits?

With a good implementation, yes, it'll stripe reads across all of the disks in the mirror.

 

[zCypher]

Sweet!

 

[T_Yamamoto]

still a waste of money for me

 

[compcons]

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.