From 3dacb8902913a4c025b5beb3fb334f9d8b6dc0ce Mon Sep 17 00:00:00 2001 From: Iustin Pop Date: Tue, 11 Sep 2007 16:20:19 +0200 Subject: Explain the read-balancing algorithm for RAID1 better in md.4 From: Iustin Pop There are many questions on the mailing list about the RAID1 read performance profile. This patch adds a new paragraph to the RAID1 section in md.4 that details what kind of speed-up one should expect from RAID1. Signed-off-by: Iustin Pop --- crc32.c | 0 crc32.h | 0 inventory | 0 md.4 | 7 +++++++ super-ddf.c | 0 5 files changed, 7 insertions(+) delete mode 100644 crc32.c delete mode 100644 crc32.h mode change 100644 => 100755 inventory delete mode 100644 super-ddf.c diff --git a/crc32.c b/crc32.c deleted file mode 100644 index e69de29..0000000 diff --git a/crc32.h b/crc32.h deleted file mode 100644 index e69de29..0000000 diff --git a/inventory b/inventory old mode 100644 new mode 100755 diff --git a/md.4 b/md.4 index cf423cb..db39aba 100644 --- a/md.4 +++ b/md.4 @@ -168,6 +168,13 @@ All devices in a RAID1 array should be the same size. If they are not, then only the amount of space available on the smallest device is used (any extra space on other devices is wasted). +Note that the read balancing done by the driver does not make the RAID1 +performance profile be the same as for RAID0; a single stream of +sequential input will not be accelerated (e.g. a single dd), but +multiple sequential streams or a random workload will use more than one +spindle. In theory, having an N-disk RAID1 will allow N sequential +threads to read from all disks. + .SS RAID4 A RAID4 array is like a RAID0 array with an extra device for storing diff --git a/super-ddf.c b/super-ddf.c deleted file mode 100644 index e69de29..0000000 -- cgit