help me in RAID concept... Post: 302487903

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Top Forums UNIX for Dummies Questions & Answers help me in RAID concept... Post 302487903 by citaylor on Friday 14th of January 2011 04:26:07 AM

01-14-2011

Registered User

Sure...if you have a concatenation, it will just join the two disks end-to-end. When it starts writing to the partition it will start on the first device and write the data. It will continue to do this until that partition has been used up, and then it will start writing to the second device, etc. This is the most basic way of getting a large partition from two smaller ones.

Stripes on the other hand, although they also allow you to have a large partition, the primary use is to vastly improve disk performance. The stripes are a pre-determined size which can be specified by the admin when the metainit is called. So for example if the stripe is 32k, and there are three devices in the stripe then the first 32k of data written to the metadevice partition would go onto the first device, the second 32k would go onto the second device, the third 32k would go onto the third device, the fourth 32k would go onto the first device again, etc, etc.
This means that when an application reads or writes a large file, all three devices can share the load. This would (in a perfect world) make the reads and writes three times faster than just having one device. So disk performance can easily be improved by orders of magnitude by using this method. It is important, however, to consider your data and how big the stripes are, as this can make a huge difference on the end performance.

I hope this helps...

citaylor

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LEARN ABOUT MINIX

partitio

PARTITION(8)						      System Manager's Manual						      PARTITION(8)

NAME

       partition - make a partition table

SYNOPSIS

       partition [-mf] device [type:]size[+*] ...

DESCRIPTION

       Partition  makes  a partition table on device using the types and sizes given.  It may be used in combination with repartition(8) for auto-
       matic installation of Minix.

       You may give up to four type:size[+*] specifications for the partitions.  You may also specify holes before, between, and after the  parti-
       tions.  A hole differs from a partition specification by not having a type.

       The first hole is by default 1 sector to make space for the primary bootstrap and the partition table.  The other holes are 0.

       The  type  field is the type of the partitition in hexadecimal.	The size field is the partition's size in sectors.  The + or * may option-
       ally be added to indicate that the partition must be expanded to contain any leftover space on the device or to mark the partition active.

       Partitions are padded out to cylinder boundaries, except for the first one, it starts on track 1.  Some operating systems care about  this.
       Minix and MS-DOS do not.

OPTIONS

       -m     Minix only, no need to pad partitions.  This is the default for subpartition tables.

       -f     Force making a partition table even if the device is too small.

EXAMPLE

       partition /dev/hd0 01:16384 81:40000 81:2880* 06:20000+

       Partitions  disk 0 into an 8 Mb DOS partition, 20 Mb Minix /usr, 1.44 Mb Minix / (active), and a DOS partition of at least 10 Mb at the end
       of the disk.  (06:0+ would have been ok too, it's just a sanity check.)

SEE ALSO

       hd(4), part(8), repartition(8).

AUTHOR

       Kees J. Bot (kjb@cs.vu.nl)

																      PARTITION(8)