BH2 said:
Hi gusy,
still learning, can someone explain in laymans terms RAID, which Raid
would
be the better for 2 SATA Drives. Thanks for your advice and help
In laymen's terms: RAID = Redundant Array of Independent Disks. There are
many types of RAID, and actually some that are called RAID, but aren't
really RAID.
First there is RAID 0, which is two or more disks that are seen by the
system as one large disk. This isn't really RAID by definition because
there is no redundancy, and therefore no way to fix the RAID if a drive
goes bad. You lose everything. Since there are multiple disks involved, the
chance of catastrophe goes up as a multiple of how many disks are in the
RAID setup. Therefore, you're twice as likely to gave a problem with 2
drives, than with one, and 4 times as likely with 4 drives. RAID 0 is
probably the fastest RAID out there because of its lack of redundancy, so
there is less overhead. With large files and lots of disk access, RAID 0
can be incredibly fast. You've heard of terms like ATA 100, ATA 133, Serial
ATA 150, etc., right? Usually with a single drive, you only momentarily
touch those lofty ceilings of 100 MB/s and higher. After that momentary
sprint, you're faced with the actually physical throughput that happens as
fast as the drive's heads can collect the data off the platters. With a 4
drive RAID and some fast drives, you could constantly push data through at
that high rate. There is penalty for using RAID, though. On short reads
with small files, there is an overhead of seeing multiple drives as one and
therefore a performance penalty. However, it more than pays off when
loading the OS, opening a video, or anything else that's a fairly large
file, and that's where you most want the performance.
Second, is RAID 1, which is redundant, and therefore a true RAID. It
basically makes an instantaneous copy of what it writes on one drive to
another, therefore making a backup. It's that simple. Tests have shown
that, while RAID 1 saves you time by allowing you to no have to make
backups, there is a serious performance hit due to the overhead involved.
Expect much slower drive access.
Then there is RAID 0+1 where it has one drive for writing redundantly to,
and two drives seen as one to the system for improved performance. I don't
know much about the performance of this setup, but I expect it to be only
slightly faster than having a single drive.
Professional servers often use RAID 5, where you have multiple disks for
speed, and redundancy, and it's fairly fast when coupled with a dedicated
RAID card complete with its own processor and memory. SCSI is traditionally
the favorite because, unlike ATA, it can write to multiple targets
simultaneously. This comes in handy when say you have a database server
that gets many requests. It also has multiple redundancy, and therefore
it's easy to just replace a drive and rebuild it if one ever goes bad.
Therefore, this setup is very secure.
Of course, there are others, but these help explain the differences.
