Anyone know if Partition Magic will work with hard drives in a RAID array?
Its nothing special, just the RAID controller on the Abit KR7A motherboard, and the drives are in RAID 0 if that is any help.
Ta.
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Anyone know if Partition Magic will work with hard drives in a RAID array?
Its nothing special, just the RAID controller on the Abit KR7A motherboard, and the drives are in RAID 0 if that is any help.
Ta.
I would not expect PM to cope with a RAID system.
BTW: Partitioning a RAID system seems to defeat the purpose of RAID.
RAID 0 is a bad idea for most users. Why are you using it?
I totally agree with that Guv..Quote:
Originally posted by Guv
BTW: Partitioning a RAID system seems to defeat the purpose of RAID.
Um, No.
When you create a RAID array the two disks are treated as one large one, and for all intents and purposes, it is. If you partition it into two smaller ones, you have just got two smaller RAID drives.
Why is RAID 0 a bad idea for most users? I have two identical hard drives, so I put them in RAID 0. How is this bad? You get improved performance and No loss in storage space. So what exactly is the disadvantage?
RAID 0 provides twice the transfer rate when it gets started, or 3/4 times the rate if more than two disks can be used in the array. It gives the appearance of one large drive with twice (or 3/4 times) the transfer rate. It does this by what is called data striping.
In an array with two disks, even addresses are on one disk and odd addresses on the other. If 6 blocks (allocation units) of data were to be written, an I/O order for blocks 1, 3, & 5 would be initiated for the first disk, and a concurrent I/O order for blocks 2, 4, & 6 would be initiated for the other disk.
One problem is that you get double the latency time and usually double the head movement time with a 2-Disk array (3/4 times with a 3/4-Disk array). Latency time averages ½ a revolution, during which time half a track of data could be written or read.
Consider writing a track full of data.With average latency, the RAID system requires a minimum of 1.5 revolutions to transfer a track of data, which is the average for the ordinary 2-disk system. Head movement is likely to be required on one or both disks, making even the best case worse for the RAID system. Note that head movement is mechanical and is measured in milliseconds, perhaps equivalent to a quarter revolution or more.
- RAID 0 with 2 disks: Average latency is one revolution (½ rev for each disk). Due to the data transfers being concurrent, the transfer time could be as low as ½ revolution, but this is best the best case (It only happens if the data transfers are exactly synchronized, beginning and ending at the same time).
- Ordinary disks: Average latency is ½ rev, followed by one revolution to write a track of data.
The above shows that for a transfer of one track of data, the RAID system is slower. For less than a track of data, the RAID system is even worse. Somewhere between 1.5 and 2 tracks of data, the RAID system breaks even, and beyond 1.5 to 2 tracks it is faster.
Hence a RAID system is a good idea if you typically transfer a lot of data with each I/O operation. This is not the case for most users.
There are two other problems with RAID 0.If you take into account the requirement for more backups, some of the gain in speed is given back.
- Head movement causes more wear & tear on a disk than anything else. Each RAID I/O tends to require head movement on two or more disks. This decreases the mean time to failure of some disk.
- If either disk in a 2-disk RAID array fails, data recovery is a nightmare. The remaining disk has every other allocation unit of a file. RAID is risky for a typical user unless there are frequent backups of the data.
My system has three disks.My system supports RAID 0, but I prefer the above organization, which minimizes head movement. The time saved due to less head movement can only be noticed by a sophisticated bench mark program, which might not even be a good model of what I usually do. However, I have less wear and tear due to less head movement, and I have images of my critical partitions. If anything goes wrong, I can easily restore my system by copying the backup images.
- OS & major applications are on the first disk.
- All data files are on the second disk.
- The OS Swap file and backups are on the third disk.
- Some CD applications are in partitions on all three disks.
Unless you have applications which transfer large amounts of data with each I/O operations, RAID 0 is a bad idea. It results in slower Disk I/O for a typical user, and has potential for disaster if a disk fails. Furthermore, it increases the probability of disk failure.
With a 2-Disk system, a typical user is likely to get more I/O efficiency by separating the data from the OS & applications than by using a 2-Disk RAID array. On a 2-Disk system, I am not sure where the OS swap file should be: With OS & applications or with Data files?