Basic raid question.

[Slash621]

If i put 2 120 gig HD's into raid arrays... how many total Gig's do ihave left.

tell me if i am right or wrong.

Raid 0 - 240 gigs really fast but if one fails its over.
Raid 1 - 120 gigs normal but perfectly backed up
Raid 1.5 - 240 gigs normal and backed up???

 

[charlie21]

Raid 0 - Bingo.
Raid 1 - Protected against drive failure, but not "backed up". If you delete some files by accident, they're gone.
Raid 1.5 - 120 GB, marginally better performance than RAID 1, but you're stuck with RAID controllers that support the very uncommon 1.5.

 

[StraightPipe]

I've never heard of 1.5 maybe you mean 1+0 or 5 (both give a backup and performance increase, but take 4 or 3 drives respectivly).

RAID0- writes every other stripe of data on each drive,
the idea is to strap 2 hard drives together so they can
go 2 times as fast (they dont actually perform THAT
fast). if you lose 1 drive than you lose all info on
both drives(ie: have to reformat)
120G+120G=240G

RAID1- writes exact same thing on 2 drives. gives you a
copy incase one drive crashes. dsnt
improve performance, but gives you a backup copy if one drive fails.
120G+120G=120G

RAID5-takes 3 drives. it's like best of both worlds.
stripes of data rotate on 2 drives and 3rd gets a
"parity note" it allows you to take data from any 2
drives and recreate the data on the 3rd.
120G+120G+120G=240G

you could also just set up the drives independent of
each other and you wouldnt have to worry about
anything, you get regular performance, and no backup,
will show as 2 drives
120G+120G= 2 120G drives

RAID 1+0 takes 4 drives. it's exacly like it sounds.
take 2 drives in raid 0 for performance, and uses 2
more drives to make a copy of each to give you back up.
120Gx4 = 240G

 

[Slash621]

i have a DFI lanparty NF2, it has a RAID 1.5 controller on it from highpoint

 

[Slash621]

also how often do hd's FAIL in raid modes?

 

[Slash621]

bump

 

[chocoruacal]

Originally posted by: Slash621
also how often do hd's FAIL in raid modes?

Anyone who could predict when hard drives fail...would be famous. You can't. Impossible. RAID has nothing to do with it. A HD can fail after 2 minutes or 10 years. The important thing to remember is that:

1. RAID is not a backup.
2. RAID doesn't make your hard drives more likely to fail. It does make you more likely to lose your data, because you are now gambling on the reliability of two drives.
3. RAID 0 is a trade off between speed and safety. One drive fails...you lose everything.

I don't use RAID 0 for anything but a temporary folder.

 

[charlie21]

Just to clarify #2 above, as long as you're using one of the RAIDs with redundancy (1, 3, 5, 1.5.....), your data is safer than if it was just on one disk or in RAID 0.

 

[rjain]

S.M.A.R.T. can usually predict when a drive is about to start losing data.

RAID 1 does give some performance benefit to reads, since you can distribute the reads across both disks. However, writes need to be done to both disks.
RAID 5 has a bit of overhead in the parity calculation.

 

[StraightPipe]

any body know where i can read up on 1.5? how many drives does it use?

Edit:I checked out an article at Tom's

apparently RAID 1.5 is actually RAID 1, but when you do a read it alternates drives skiping every other stripe. (simulating RAID0 performance on reads)
bad thing is that the drives dont get to stream out the stripes like in RAID0, because they have to skip everyother stripe. so you probly wont get real RAID0 speed on reads, and will get RAID 1 speeds (normal) for writes

 

[JustAnAverageGuy]

Anandtechs 1.5 description

It's on the bottom.

 

[Slash621]

yaeh looks like running raid 1.5 isnt really worth it in performance..

 

[OverVolt]

Heck just go RAID0 and make backups. To me the speed is well worth the chance you take. But then again i've never had a drive fail on me prematurely (5WD drives <1.5yr old none failed) But i've had some old 15Gb Maxtor variants 4-5yr old clunkers die on me. but thats no big deal.

 

[StraightPipe]

one thing to keep in mind is that it doesnt make your drives more likely to fail (RAID0). but you are more likely to loose data (because if one fails you loose 2 drives worth of data)

backups really depend on how sensitive your data is, it's just like normal IDE, back it up if it's important.

the real differences are that you can go twice as fast, and you can only do one read/wrtie at a time.