X-Git-Url: https://git.gag.com/?a=blobdiff_plain;f=docs%2Frait.txt;h=e69de29bb2d1d6434b8b29ae775ad8c2e48c5391;hb=d92f70685083588e2a7ce6bc312a735f6937b5a6;hp=c75be0c8aa68a24ac1ff4f6d8d0a5a8a06e8c4ad;hpb=e442edb4d5816c4ad107ad9e71164f845eba70ad;p=debian%2Famanda diff --git a/docs/rait.txt b/docs/rait.txt index c75be0c..e69de29 100644 --- a/docs/rait.txt +++ b/docs/rait.txt @@ -1,104 +0,0 @@ - -Chapter 10. RAIT (Redundant Array of Inexpensive Tape) Support -Prev Part II. About Tapes and Changers Next - -------------------------------------------------------------------------------- - -Chapter 10. RAIT (Redundant Array of Inexpensive Tape) Support - - -Marc Mengel - -Original text - -Stefan G. Weichinger - -XML-conversion;Updates -AMANDA Core Team - -Table of Contents - - - What_is_a_RAIT? - - Using_a_RAIT - - Disaster_Recovery - -Currently it is only integrated with the chg-manual changer script; -collaboration on integrating it with the other tape changers is needed. - - What is a RAIT? - -RAIT is an acronym for "Redundant Array of Inexpensive Tapes", where data is -striped over several tape drives, with one drive writing an exclusive-or-sum of -the others which can be used for error recovery. Any one of the data streams -can be lost, and the data can still be recovered. -This means that a 3-drive RAIT set will write 2 "data" streams and one "parity" -stream, and give you twice the capacity, twice the throughput, and the square -of the failure rate (i.e. a 1/100 failure rate becomes 1/10,000, since a -double-tape failure is required to lose data). -Similarly, a 5-drive RAIT set will give you 4 times the capacity, 4 times the -throughput (with sufficient bus bandwidth), and the square of the failure rate. -This means you can back up partitions as large as four times your tape size -with Amanda, with higher reliability and speed. - - Using a RAIT - -If you have several tape devices on your system [currently either 3 or 5 drive -sets are supported] you tell Amanda to use them as a RAIT by listing them as a -single tape device using /bin/csh curly-brace-and-comma notation, as in: - - tapedev = "rait:/dev/rmt/tps0d{4,5,6}n" - - -which means that /dev/rmt/tps0d4n, /dev/rmt/tps0d5n, and /dev/rmt/tps0d6n are -to be treated as a RAIT set. You can now mount three tapes, and label them with -amlabel, etc. -Also, you want to create a new tape-type entry, which lists an n-drive RAIT -set, for this RAIT-set. So if you were using an entry like: - - define tapetype EXB-8500 { - comment "Exabyte EXB-8500 drive on decent machine" - length 4200 mbytes - filemark 48 kbytes - speed 474 kbytes - } - - -You would want to make a new one like: - - - define tapetype EXB-8500x3 { - comment "Exabyte EXB-8500 3 drive stripe on decent machine" - length 8400 mbytes - filemark 200 kbytes - speed 948 kbytes - } - - -and change your tapetype entry to: - - tapetype EXB-8500x3 - - -to tell Amanda about the multiple drive set. - - Disaster Recovery - -To assist in disaster recovery (as well as changer scripts) the Amanda package -now also includes amdd, which is a simple dd(1) replacement which supports -(only) the "if=xxx", "of=xxx", "bs=nnn[kMb]" "skip=nnn" and "count=nnn" -options, but which can read and write RAIT tapesets. -Using amdd and your usual Amanda unpack instructions will suffice for disaster -recovery from RAIT tape-sets. - -Note - -Refer to http://www.amanda.org/docs/rait.html for the current version of this -document. -------------------------------------------------------------------------------- - -Prev Up Next -Chapter 9. chg-scsi Home Chapter 11. Printing of Labels -