rlemieux
01-20-2002, 02:18 AM
I know a little about RAID. I know it has to do with dual hard drives, but beyond that I am kinda confused. Can anyone fully explain it and tell me why I would want it or why I shouldnt. Thanks.
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Bovon
01-20-2002, 02:50 AM
I know very little about raid sence I am not that interested, but check out the following thread here for some explainations:
http://www.sysopt.com/forum/showthread.php?s=&threadid=93766
http://www.sysopt.com/forum/showthread.php?s=&threadid=93766
lavazzza
01-20-2002, 02:56 AM
RAID- Random Array of Inexpensive Disks
Whether raid can help depends mainly on what you intentions are. Depending upon which raid level you use, you will get fault tolerance and improved system performance in regards to you hard drive. As a minimum two hard drives are needed.
Raid level 0 - disk striping without parity. Without getting bogged down in the technical aspects, this option is geared toward increasing read/write performance since the information is split and written to two disks. The obvious advantage is that with a raid card or a SCSI connection, the information is being simultaneously written to both disks, theoretically doubling the performance of these processess.
Raid level 1 - disk mirroring. Two hard disks are on the same controller. As information is written to one disk, it is also written to the second. This is an expensive option because the second drive is purely for fault tolerance purposes and if there are 2 20GB drives you will still have only 20GB of storage. If the disk controller goes down, you have lost both. A better option here is disk duplexing which has two drives on two controllers.
Raid level 2 - uses Hammering error correction codes for drives which do not have built-in error detection. SCSI drives support built in error detection.
Raid level 3 - Stripes data at a byte level across several drives with the parity stored on one drive
Raid level 4 - Stripes data at a block level across several drives with parity stored on one drive. Both levels 3 and 4 are good for read performance, but slow down for write on small random bits of information but fair for large sequential blocks of information. Inexpensive because only one drive stores the parity.
Raid level 5 - disk striping with parity. Similar to level 0 because it writes across multiple disks in a stripe set. Provides good fault tolerance because if one disk fails the parity is stored on the other disks and the information can be regenerated. In case of disk failure this can be a memory hog. Requires at least 3 drives.
There are three other hybrid raid levels
Raid 10 - dual level array utilizing multiple raid 1 sets into a single array
Raid 50 - dual level array utilizing multiple raid 5 sets into a single array
Raid 15 - created by a striped ste with parity using multiple mirrored pairs as components
I hope this helps more than it hurts.
Whether raid can help depends mainly on what you intentions are. Depending upon which raid level you use, you will get fault tolerance and improved system performance in regards to you hard drive. As a minimum two hard drives are needed.
Raid level 0 - disk striping without parity. Without getting bogged down in the technical aspects, this option is geared toward increasing read/write performance since the information is split and written to two disks. The obvious advantage is that with a raid card or a SCSI connection, the information is being simultaneously written to both disks, theoretically doubling the performance of these processess.
Raid level 1 - disk mirroring. Two hard disks are on the same controller. As information is written to one disk, it is also written to the second. This is an expensive option because the second drive is purely for fault tolerance purposes and if there are 2 20GB drives you will still have only 20GB of storage. If the disk controller goes down, you have lost both. A better option here is disk duplexing which has two drives on two controllers.
Raid level 2 - uses Hammering error correction codes for drives which do not have built-in error detection. SCSI drives support built in error detection.
Raid level 3 - Stripes data at a byte level across several drives with the parity stored on one drive
Raid level 4 - Stripes data at a block level across several drives with parity stored on one drive. Both levels 3 and 4 are good for read performance, but slow down for write on small random bits of information but fair for large sequential blocks of information. Inexpensive because only one drive stores the parity.
Raid level 5 - disk striping with parity. Similar to level 0 because it writes across multiple disks in a stripe set. Provides good fault tolerance because if one disk fails the parity is stored on the other disks and the information can be regenerated. In case of disk failure this can be a memory hog. Requires at least 3 drives.
There are three other hybrid raid levels
Raid 10 - dual level array utilizing multiple raid 1 sets into a single array
Raid 50 - dual level array utilizing multiple raid 5 sets into a single array
Raid 15 - created by a striped ste with parity using multiple mirrored pairs as components
I hope this helps more than it hurts.
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