[Date Prev][Date Next] [Thread Prev][Thread Next] [Date Index] [Thread Index]


On Thu, Nov 10, 2005 at 09:57:02AM -0800, lordSauron wrote:
> On 11/10/05, Albert Dengg <a_d@gmx.at> wrote:
> > well it has to map the raid device to the real discs...like with all
> > raid levels
> >
> > also...
> > raid 0 isnt really raid...
> > raid means _redundant_ array of independet/inexpensive discs...
> > and raid 0 isnt redundant at all
> I'm interested in RAID 0 b/c I want drive speed, not drive
> reliability.  I've got a full-tower ATX case which runs amazingly cool
> and quiet, so I'm not concerned with my drives freaking out and
> spontaniously dying.
> So the current installer does not support the motherboard's RAID,
> which is slower, but what about setting up linux's kernel's RAID?  Can
> the current Sarge installer do that?
> Also, I know about RAID 0, 1, and 50, but what on earth is RAID 5 and
> 6?  I think RAID 5 has to do with networked JBODs, but I'm not sure...

RAID0 (not raid) is stripping data over multiple disks to increase

RAID1 is mirroring data across 2 disks to increase reliability (at the
cost of half your disk space).

RAID 3 4 and 5 are stripping with parity across multiple devices to
increase speed and reliability, although it requries xor calculations
liek there is no tomorrow and hence often is only done with a hardware
xor engine for acceleration.  Modern CPUs with good MMX/SSE/etc
algorithms are not bad at it either though.  Raid 5 stripes the parity
data across the disks to avoid a heavy load on a single disk storing
parity data.  Raid 3 and 4 store the parity data on one device only.
Costs you one disk worth of disk space out of your total space (so you
can 700G if you have 8 * 100G drives in raid 3/4/5).

RAID6 is RAID5 with ECC.  It stores a second set of parity data to allow
error correction.  It costs you two disks worth of space out of the
total (so you get 600G if you have 8 * 100G drives).  It can I believe
tolerate 2 disk failures without data loss (although at that point you
get no error correction anymore).

Supposedly from what I have seen, RAID10 is disks stripped, then mirror
two identical size RAID0s, while RAID01 is disks mirrored, and then
stripe the mirrors, and RAID50 is two RAID5s mirrored.

Len Sorensen

Reply to: