Are RAID setups necessary?

[El Kabong]

Ive never even had a second thought about these kinds of arrays until i got my second hard drive. For the 7+ years ive been using computers ive never had an HDD bust out on me, be it retail or custom made... But now that i actually have the ability to CREATE such a thing, i cant help but feel paranoid about losing all my files...


What do you guys think?

 

[fri2219]

For the way most people use their personal computers, absolutely not.

If, for some reason, you can't back up your data to another device, then mirroring probably has some merit.

 

[swatbat]

i cant help but feel paranoid about losing all my files...

Get a backup program and backup to something external that is not hooked into the system when it is not in use.

Raid is for uptime, not data backup.

 

[Xipher]

swatbat hit the nail on the head when it comes to RAID mirroring (1) or storage + parity (5). These two are designed to minimize downtime, and RAID 5 also adds the ability to build some larger volumes then a single drive can do, with some fault tolerance. RAID striping (0) is pretty much all about performance with out any fault tolerance, so if one disk dies you loose your data. We have a number of servers where I work using RAID 1 or RAID 5, and you might be surprised how often drives can fail when they undergo constant use but with the proper hardware you can replace the drive and rebuild with out ever taking the system offline. Since I started working I have seen one instance of a double drive failure in a RAID 5 and this is why backups are important.

 

[MrCrispy]

"RAID is NOT backup" x 100 !!

Having said that -

- RAID comes in handy for combining multiple disks into a logical drive with some measure of redundancy.
- performance gains from striping
- modern chipsets and cpu's make hw-assisted sw raid free and usable for the masses
- not everything needs to be backed up (like program installs) but it does need to be available. RAID is a good fit

 

[swatbat]

Since I started working I have seen one instance of a double drive failure in a RAID 5 and this is why backups are important.

Only times I've seen more then one drive fail are when they got zapped by lightning(direct hit to building that fried everything, the ups's did nothing) and with things like power supply failures. I've also seen an apple xserve get flooded once where I water pipe broke and the fans sucked in a lot of water.

Bigger issue is a controller card failure. I've seen this a few times and have seen them screw up data.

Every server we run uses raid and some desktops use it(important clients that need the uptime). Home use it is for the most part overkill.

 

[unhappy_mage]

Is it necessary, in the global sense? Yes, certainly. Banks need it, all the way down to medium-small institutions down to those that actually use their computers as glorified file cabinets.

Is it necessary for you? I dunno. What do you do? What makes you think that it might be a good choice? What kind of money do you have to play with if you discover there are advantages to a RAID array?

As stated above, RAID is not backup in any way, shape or form. All it does is keep the most recent copy of your data online if hardware failures happen (and you have enough redundancy in the rest of the machine that *any* piece can fail). If you delete a file by mistake, or accidentally remove all the ID3 tags from your music collection, or the database with your life on it gets corrupted, all that data is just as gone as if it were on a single disk. The only backup that's even remotely reliable is one that is sitting on a shelf in another building (preferably another state), tested to be restorable from, and with the power unplugged from it. RAID meets none of these criteria.

 

[MrCrispy]

I'd like to add that a lot of enthusiasts like to use RAID 0 for the performance gains it gives. Every single benchmark I've read goes against that claim - at most under ideal load scenarios you can squeak out a few % extra, while doubling the risk of total data loss.

RAID 1 is the exact opposite - wasting an entire disk for redundancy. IMO RAID 5 is the only way to go if you have to do RAID, and something like Intel Matrix RAID will let you mix and match for optimal results.

 

[swatbat]

I'd like to add that a lot of enthusiasts like to use RAID 0 for the performance gains it gives. Every single benchmark I've read goes against that claim - at most under ideal load scenarios you can squeak out a few % extra, while doubling the risk of total data loss.

RAID 1 is the exact opposite - wasting an entire disk for redundancy. IMO RAID 5 is the only way to go if you have to do RAID, and something like Intel Matrix RAID will let you mix and match for optimal results.

Yes in desktop use raid 0 is pretty much a waste. Does have some uses in some server setups but generally on a desktop you will not notice.

As far as your take of raid 1 and 5 you need to consider some other things. One raid 1 is a cheap way to increase uptime. 2 with raid 1 if you have a controller failure you can gererally hook a single drive into a normal controller and pull data. Once you get into raid 3,5, or 6 this becomes more of an issue unless you have a controller that is compatable with how the first raid controller set them up. This can be a big deal if you want to recover some things off a system that goes down durring the middle of a day or something where your backup is a few hours old or older.

Another thing is the cpu usage and controller cost. Raid 1 doesn't tax the cpu even with a software raid or card that relys on software like a software raid 5 like that intel matrix would. Pretty much it is no big deal. With raid 5 you will see a pretty big cpu load hit or speed issues. You really need a controller card with a hardware raid engine. These start at about 300 bucks or so. Also I am really against using any raid above 0 or 1 off a motherboard because if the board dies it can make getting data off a lot harder. A add in card generally has a better chance of lasting longer(doesn't have all the power circuits a motherboard has) and makes upgrades to a system a little better. Factor in the cost added for raid 5 and the cost of that second drive for raid 1 just seems to go away.

Another thing to consider is a raid 5 with only a few drives like 3 generally has a slower write speed then a single disk or raid 1. If you have a bunch of drives and a hardware raid card this issue goes away(and read speed really goes up)

In the case of my clients that have raid on desktops or workstations it is raid 1. No reason to spend the extra money on 5. With their servers generally we have a raid 1 for the os and either a second raid 1 or a raid 5 for data. Depends on their needs. Smaller setups have a single raid 1 in them. In most cases unless they have a lot of data we stick with 2 raid 1s.

On a side note my home server has a intel sas raid card in it. Running a 3 drive raid 5 using sata 300 drives. Plan on adding more down the road(supports 8 sata drives or a shit load of sas using extenders). Run a hd tach and the speed is about the same as a single sata drive as a second drive in the system(raid 5 is a boot drive). Interesting thing is the cpu usage on the onboard controller will spike to 10%. Intel raid card running raid 5 is about 1%. Mind you this is a card that retails for like 700 bucks. If I threw in one of those 100 dollar software raid 5 cards for this same boot volume speed would be cut in half and cpu usage would spike. If the box did nothing but host files at home running linux or something that would be fine. Running it as a true server doing a lot of other things(hell even if it was just a desktop) would not be. FYI I have one of those 100 dollar rocket raid cards sitting around somewhere. Thew it in to test something in windows 64 while I researched what raid card to get. Old raid 5 card wasn't compatable with server 64. It was a first gen sata.