ButĬombining several partitions on one disk usually does not make sense, Usually the devices that are used to build a RAIDĭevice are partitions on disks, not necessarily entire disks. Note that the words "device" and "disk" are supposed to mean about We assume that the disks are equally fast, which may not always be Used as the performance of one disk in the array, in MB/s. In the array, unless otherwise mentioned. The letter S is the size of the smallest drive At all times the letter N is used toĭenote the number of active disks in the array (not counting When describing RAID setups, it is useful to refer to the number ofĭisks and their sizes. Treat any aspects of Software RAID in other operating system kernels. This HOWTOĭoes not treat any aspects of Hardware RAID. In this HOWTO the word "RAID" means "Linux Software RAID". Another level, "linear" has emerged,Īnd especially RAID level 0 is often combined with RAID level 1. Used in very specialized systems (and in fact not even supported by Today some of the original RAID levels (namely level 2 and 3) are only Non-redundant array of disk drives as a RAID-0 array. Redundant array architectures, it has become popular to refer to a The Berkeley paper, each providing disk fault-tolerance and each offeringĭifferent trade-offs in features and performance. However, disk arrays can be made fault-tolerantīy redundantly storing information in various ways.įive types of array architectures, RAID-1 through RAID-5, were defined by MTBF of an individual drive, divided by the number of drives in the array.īecause of this, the MTBF of an array of drives would be too low for manyĪpplication requirements. The Mean Time Between Failure (MTBF) of the array will be equal to the This array of drives appears to the computer as a single logical storage Independent disk drives into an array of disk drives which yields performanceĮxceeding that of a Single Large Expensive Drive (SLED). The basic idea of RAID was to combine multiple small, This article described various types of disk arrays, referred to by theĪcronym RAID. In 1987, the University of California Berkeley, published an article entitledĪ Case for Redundant Arrays of Inexpensive Disks (RAID). Back up all your data before experimenting with This information, is in any way correct, nor suited for any use Risk! There is no guarantee whatsoever, that any of the software, or BeĪware, that you use the RAID software and this information at your own If you lose all your data, your job, get hitīy a truck, whatever, it's not my fault, nor the developers'. 1.1 DisclaimerĪll information herein is presented "as-is", with no warrantiesĮxpressed nor implied. Some of the information in this HOWTO may seem trivial, if you know Important features present in the new-style RAID software. Support in standard 2.0 and 2.2 kernels is buggy and lacks several Not have direct support for the new-style RAID described in this If you want to use the new-style RAID with 2.0 or 2.2 kernels, you The linux-raid mailing and various other people. Østergaard based on a large number of emails between the authorĪnd Ingo - one of the RAID developers -, The howto was originally written by Jakob It does not describe the "old-style" RAIDįunctionality present in 2.0 and 2.2 kernels. This HOWTO describes the "new-style" RAID present in the 2.4 and 2.6 8.1 Recovery from a multiple disk failure.7.7 Sharing spare disks between different arrays.7.6 Converting a non-RAID RedHat System to run on Software RAID.5.2 Downloading and installing the RAID tools.Many considered far more stable that the older RAID support already in Support is available as patches to Linux-2.0 and Linux-2.2, and is by Used by Linux-2.2 kernels shipped from some vendors. That is the standard in Linux-2.4, and it is the version that is also ItĪddresses a specific version of the Software RAID layer, namely theĠ.90 RAID layer made by Ingo Molnar and others. This HOWTO describes how to use Software RAID under Linux. This HOWTO is deprecated the Linux RAID HOWTO is maintained as a wiki by the The Software-RAID HOWTO Jakob Østergaard Emilio Bueso
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