[kudu] 02/02: [docs] add info on quick hole punching test

[al...@apache.org]

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alexey pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/kudu.git

commit 4c5b67d68b8207f95cd35e30d5ff193b6ac6be12
Author: Alexey Serbin <al...@apache.org>
AuthorDate: Fri Aug 27 19:48:22 2021 -0700

    [docs] add info on quick hole punching test
    
    Change-Id: Ibac1af744bb163144d6c19d9e0f1aac3b5fba6e9
    Reviewed-on: http://gerrit.cloudera.org:8080/17814
    Tested-by: Kudu Jenkins
    Reviewed-by: Andrew Wong <aw...@cloudera.com>
---
 docs/troubleshooting.adoc | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/docs/troubleshooting.adoc b/docs/troubleshooting.adoc
index 95a572f..8433a16 100644
--- a/docs/troubleshooting.adoc
+++ b/docs/troubleshooting.adoc
@@ -68,6 +68,19 @@ Exchange post] for details.
 Without hole punching support, the log block manager is unsafe to use. It won't
 ever delete blocks, and will consume ever more space on disk.
 
+You can run the following sequence of commands on a mounted file system to
+check whether it supports hole punching (the originally allocated 10MiB
+turns into 5MiB after punching a 5MiB hole in the file at 1MiB offset):
+
+----
+$ dd if=/dev/zero of=hole_punch bs=1M count=10 2>/dev/null
+$ du -h hole_punch
+10M     hole_punch
+$ fallocate -p -o 1M -l 5M hole_punch
+$ du -h hole_punch
+5.0M    hole_punch
+----
+
 If you can't use hole punching in your environment, you can still
 try Kudu. Enable the file block manager instead of the log block manager by
 adding the `--block_manager=file` flag to the commands you use to start the master