Stux
MVP
- Joined
- Jun 2, 2016
- Messages
- 4,419
I tested hot-swap on my server that I'm commisioning today, and the kernel crashed because of this known issue
https://forums.freenas.org/index.php?threads/swap-with-9-10.42749/
In response I've written a script:
I'm simply running it off a cron job every hour at the moment. If there's no swap in use, it takes no time.
If you have "Redirect Output" unticked, you'll get an email if there was swap in use.
This was based on a simpler version of the script in this post, but this version is much better and will actually work reliably.
Here is the script:
https://forums.freenas.org/index.php?threads/swap-with-9-10.42749/
In response I've written a script:
Code:
# This script is designed to page in used swap on any device that has swap in use on # a FreeNAS system. You would want to run this periodically to help ensure that swap # is not in use on a device which may fail at any time, for example, a drive in a raid set
I'm simply running it off a cron job every hour at the moment. If there's no swap in use, it takes no time.
If you have "Redirect Output" unticked, you'll get an email if there was swap in use.
This was based on a simpler version of the script in this post, but this version is much better and will actually work reliably.
Here is the script:
Code:
#!/usr/local/bin/perl
# This script is designed to page in used swap on any device that has swap in use on
# a FreeNAS system. You would want to run this periodically to help ensure that swap
# is not on use on a device which may fail at any time, for example, a drive in a raid set
#
# It accomplishes this by swapoff/swapon a given device rather than swapoff all devices,
# the idea being that if swap was actually necessary, then the system will always have access
# to swap is swap is never fully disabled.
#
# This is in response to an issue that became apparent on FreeNAS 9.10
# https://forums.freenas.org/index.php?threads/swap-with-9-10.42749/
#
# The script does nothing if there is no swap in use.
#
# To use, simply run via cron. Or directly when needed.
#
# If debug = 1, and you untick "Redirect Output" in FreeNAS Add Cron Job,
# you'll get an email only when swap was paged in.
#
# This script lives at:
# https://forums.freenas.org/index.php?threads/script-to-pagein-any-used-swap-to-prevent-kernel-crashes.46206/
#
# stux
# VERSION HISTORY
#####################
# 2016-09-21 Initial Version
# 2016-09-21 Tightenned swapinfo grep to only use /dev/*.eli devices. This prevents a potential
# issue after hot swapping devices.
# 2017-02-02 Fixed cosmetic issue. Bytes -> KiBs
###############################################################################################
## CONFIGURATION
################
## DEBUG LEVEL
## 0 means no output. 1,2,3,4 provide more verbosity
## 1 output only if paging in. If run from cron, this means you'll only get an email if
## swap was in use.
## 2 output startup message and at least nothing done message
## 3 more.
## 4 etc.
$debug = 1;
## PAGEIN ALL
## A debug option which is used to verify functionality even if there is no swap in use
## 0 means only pagein active swap devices. You should use 0.
## 1 means pagein all devices.
$pagein_all = 0;
#modify nothing below here
###############################################################
use POSIX qw(strftime);
dprint( 1, "Paging in swap...\n" );
pagein_swap_devices( get_swap_devices());
######### SUBS
# returns a nested list of active swap devices. Each item in the list is an array,
# [0] is the device
# [1] is the bytes used
sub get_swap_devices
{
my $swapinfo_output = `swapinfo | grep "/dev/.*\.eli"`;
chomp $swapinfo_output;
dprint(1,"swapinfo:\n$swapinfo_output\n");
my @swap_lines = split("\n", $swapinfo_output );
dprint_list(3,"swap_lines", @swap_lines);
my @swap_devs = ();
foreach my $line (@swap_lines)
{
dprint(3,"$line\n");
my @vals = split(" ", $line);
# [0] = device
# [1] = 1K-blocks
# [2] = Used
# [3] = Avail
# [4] = Capacity
if( $vals[2] > 0 || $pagein_all )
{
dprint(2, "Adding $vals[0] with $vals[2]KiB of swap to page in list.\n" );
push @swap_devs, [$vals[0],$vals[2]];
}
}
return @swap_devs;
}
#pages in a device
sub pagein_swap_device
{
my ($device,$used) = @_;
dprint(0,"Paging in $used KiBs on $device\n");
`swapoff $device`;
`swapon $device`;
return;
}
sub pagein_swap_devices
{
my @devs = @_;
if( @devs > 0 )
{
foreach my $devinfo (@devs)
{
my $dev = $devinfo->[0];
my $used = $devinfo->[1];
#dprint(0, "dev: $dev used: $used\n");
pagein_swap_device($dev,$used);
}
}
else
{
dprint(1,"No swap was paged in as no swap was used on any device\n");
}
return;
}
sub build_date_string
{
my $datestring = strftime "%F %H:%M:%S", localtime;
return $datestring;
}
sub dprint_list
{
my ( $level,$name,@output) = @_;
if( $debug > $level )
{
dprint($level,"$name:\n");
foreach my $item (@output)
{
dprint( $level, " $item\n");
}
}
return;
}
sub dprint
{
my ( $level,$output) = @_;
# print( "dprintf: debug = $debug, level = $level, output = \"$output\"\n" );
if( $debug > $level )
{
my $datestring = build_date_string();
print "$datestring: $output";
}
return;
}
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