From 7e26b9393232c58e1c563f15d7ac412d8bbbffa1 Mon Sep 17 00:00:00 2001 From: David Sterba Date: Wed, 15 Jan 2020 17:14:17 +0100 Subject: [PATCH] btrfs-progs: docs: update scrub Clarify status file updates after cancel, io schedulers. Signed-off-by: David Sterba --- Documentation/btrfs-scrub.asciidoc | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) diff --git a/Documentation/btrfs-scrub.asciidoc b/Documentation/btrfs-scrub.asciidoc index 03f7f008..081d3a08 100644 --- a/Documentation/btrfs-scrub.asciidoc +++ b/Documentation/btrfs-scrub.asciidoc @@ -25,7 +25,8 @@ The user is supposed to run it manually or via a periodic system service. The recommended period is a month but could be less. The estimated device bandwidth utilization is about 80% on an idle filesystem. The IO priority class is by default 'idle' so background scrub should not significantly interfere with -normal filesystem operation. +normal filesystem operation. The IO scheduler set for the device(s) might not +support the priority classes though. The scrubbing status is recorded in '/var/lib/btrfs/' in textual files named 'scrub.status.UUID' for a filesystem identified by the given UUID. (Progress @@ -36,16 +37,20 @@ will continue from the last saved position. SUBCOMMAND ---------- *cancel* |:: -If a scrub is running on the filesystem identified by 'path' cancel it. +If a scrub is running on the filesystem identified by 'path' or 'device', +cancel it. + If a 'device' is specified, the corresponding filesystem is found and *btrfs scrub cancel* behaves as if it was called on that filesystem. +The progress is saved in the status file so *btrfs scrub resume* can continue +from the last position. *resume* [-BdqrR] [-c -n ] |:: Resume a cancelled or interrupted scrub on the filesystem identified by -'path' or on a given 'device'. +'path' or on a given 'device'. The starting point is read from the status file +if it exists. + -Does not start a new scrub if the last scrub finished successfully. +This does not start a new scrub if the last scrub finished successfully. + `Options` + @@ -53,12 +58,15 @@ see *scrub start*. *start* [-BdqrRf] [-c -n ] |:: Start a scrub on all devices of the filesystem identified by 'path' or on -a single 'device'. If a scrub is already running, the new one fails. +a single 'device'. If a scrub is already running, the new one will not start. + -Without options, scrub is started as a background process. +Without options, scrub is started as a background process. The automatic +repairs of damaged copies is performed by default for block group profiles with +redundancy. + The default IO priority of scrub is the idle class. The priority can be configured similar to the `ionice`(1) syntax using '-c' and '-n' options. +Note that not all IO schedulers honor the ionice settings. + `Options` +