Wieger Bontekoe

When you are running out of diskspace you can purge the MySQL binary logs to free up some space

mysql> PURGE BINARY LOGS BEFORE 'yyyy-mm-dd hh:mm:ss';

Sometimes you are already on 99% disk space and need more drastic methods. This requires manually removing the logfiles.

systemctl stop mysql
cd /var/llog/mysql && a=`ls |grep -v relay |grep bin.index` && b=`wc -l <$a` ; c=`echo $(($b/2))` |xargs -l rm ; echo $c | head -n $b $a |cut -d "/" -f2 && sed 1,$c\d $a -i
systemctl start mysql

Make sure nvme-cli is installed:

$ sudo apt install nvme-cli

Check for availible nvme disks:

$ sudo nvme list
Node             SN                   Model                                    Namespace Usage                      Format           FW Rev  
---------------- -------------------- ---------------------------------------- --------- -------------------------- ---------------- --------
/dev/nvme0n1     S4EVNFXXXXXXXX9972H      Samsung SSD 970 EVO Plus 500GB           1          26,60  GB / 500,11  GB    512   B +  0 B   2B2XXXXXM7

With nvme-cli you can now check the internal temperature, disk usage, power cycles, and much more:

$ sudo nvme smart-log /dev/nvme0
Smart Log for NVME device:nvme0 namespace-id:ffffffff
critical_warning                    : 0
temperature                         : 40 C
available_spare                     : 100%
available_spare_threshold           : 10%
percentage_used                     : 0%
data_units_read                     : 90935
data_units_written                  : 119679
host_read_commands                  : 4491381
host_write_commands                 : 2370351
controller_busy_time                : 8
power_cycles                        : 34
power_on_hours                      : 9
unsafe_shutdowns                    : 1
media_errors                        : 0
num_err_log_entries                 : 0
Warning Temperature Time            : 0
Critical Composite Temperature Time : 0
Temperature Sensor 1                : 40 C
Temperature Sensor 2                : 38 C
Thermal Management T1 Trans Count   : 0
Thermal Management T2 Trans Count   : 0
Thermal Management T1 Total Time    : 0
Thermal Management T2 Total Time    : 0

After installing this version my mouse became laggy and also my headphones. Here is the fix:

# HANDLE="$(hcitool con | grep '<Bluetooth Mouse mac address>' | awk '{print $5}')"  # get the device handle
# hcitool lecup --handle $HANDLE --latency 0 --min 6 --max 8

Fio which stands for Flexible I/O Tester is a free and open source disk I/O tool used both for benchmark and stress/hardware verification that i mainly use for benchmarking ceph or specific ssd harware.

When using an SSD make sure it’s pre-warmed. This can be done using the dd command:

dd if=/dev/zero of=/dev/xvdb bs=100M &

After this you can start performance measurement with fio. My advice is to run this test for 6 to 8 hours in order to get real data out of it.

fio --filename=/dev/nvmeXnXpX --direct=1 --rw=randwrite --refill_buffers --norandommap --randrepeat=0 --ioengine=libaio --bs=128k --iodepth=16 --numjobs=1 --time_based --runtime=86400 --group_reporting –-name=benchtest

This command will run for 24 hours and perform write-only workload of 128k blocks on a single process.

Random Read test

sudo fio --name=randread --ioengine=libaio --iodepth=16 --rw=randread --bs=4k --direct=0 --size=512M --numjobs=4 --runtime=240 --group_reporting

This will use 4 processes, run for 2 minutes and only perform read iops.

Random Write test

sudo fio --randrepeat=1 --ioengine=libaio --direct=1 --gtod_reduce=1 --name=test --filename=random_read_write.fio --bs=4k --iodepth=64 --size=4G --readwrite=randrw --rwmixread=75

This will to a read/write test on a 4 GB file.

Running Ubuntu 18.04 i ran out of disk space on my main partition. I increased disk space in VMware and needed to expand the partitions from within Ubuntu. Start with scanning for changes on your disk

echo 1 > /sys/class/block/sda/device/rescan

Verify that you can see the new (correct) disk space using:

fdisk -l

Create a new partition using “cfdisk”, navigate to the free space and hit “new”. After that hit Write to make sure the partition table gets written. Close cfdisk and either reboot or rescan to update your partition table. Now it’s time to add the disk space. First, find the new partition number:

fdisk -l

In my case sda3 was created to i’m going to create a new volume on it

pvcreate /dev/sda3

now extent my volume group with the newly added volume:

vgextend ubuntu-dev-box /dev/sda3

Extend the volume with all available (new) disk space:

lvextend -l+100%FREE /dev/ubuntu-dev-box/root

Now resize the filesystem:

resize2fs /dev/mapper/ubuntu--dev--box--root