wild_block_device_filler

What is this

A simple Perl program to fill a partition or a disk with lots of 0x00, 0xFF or alphanumerics. Meant for Linux/Unix.

It calls the tool lsblk(8) to get information about available block devices, so you must have that on your system!

At 650+ lines, it looks complex, but the complexity resides in the handling of the input options mainly.

Good for:

Speed testing (how does throughput change when writing 100 physical blocks vs 1000 physical blocks?)
Erasing the disk, filling it with zeros.
Seeing what the SSD does, and whether TRIMs did anything etc.

Status

Works perfectly well on Fedora 29 ... Fedora 36 (and counting).

License

The UNLICENSE: https://unlicense.org/

This is free and unencumbered software released into the public domain.

How to deploy

Make sure the lsblk(8) tool exists on your machine.
Put the single Perl script wherever you prefer. Make it executable.
Make sure needed Perl modules have been installed.

Non-core Perl modules that you need are:

JSON::Parse
File::Sync

On systems that use dnf as installer:

dnf install perl-JSON-Parse perl-File-Sync

Usage

To be able to write to the block device, this program must (most probably) be run as root!

The --help option says:

Fill a partition or a disk with meaningless data.

--dev=<DEV>       Device file, must be given. '/dev/sdbx', 'sdbx', '/dev/sdg', 'sdg'
                  are accepted here.

--debug           Write debugging output to stderr.

--sync            Call fdatasync(2) after each write operation, flushing data to disk. 
                  Recommended otherwise it looks as if the program is very fast, but
                  it just fills up the memory buffers.

--fillpat=<PAT>   Fill pattern. Currently there is:
                  > 'zero','0' for 0x00
                  > 'one','1'  for 0xFF
                  > 'alpha'    for 'ABCD...'
                  > 'moon'     for the message from Iain M. Banks' 'The Algebraist'
                  Default is: alpha

--chunksize=<SZ>  We write "chunks", not blocks. A chunk is an array of bytes sized 
                  at several KiB, MiB or multiples of the disk's PHYSICAL BLOCK SIZE
                  (amount of data that the disk prefers to read/write in one operation,
                  e.g. 4K) or multiples of the disk's LOGICAL BLOCK SIZE (smaller or equal
                  to the physical block size, for fine-grained, but slow addressing).
                  This sets the chunk size. Format is <num><unit>, where <unit> is one of:
                  > Nothing or 'B' for Byte
                  > 'K' for KiB
                  > 'M' for MiB
                  > 'P' for physical blocks
                  > 'L' for logical blocks
                  Default is: 1024L

When you start the program (on the command line, naturally) using for example:

wildly_fill_block_device.pl --dev=sdb1 --fillpat 0 --chunksize=1024P --sync

It will pointedly ask you first:

Going on will DESTROY device /dev/sdb1 -- are you sure to continue? Type YES!!

If you decide to proceed, you will get an information scroll:

Wrote:   2658 chunks,   1329.00 MiB, 1.09% - Overall: 73.67 MiB/s - Recent: 73.87 MiB/s - time taken: 00:00:18 - ~time remaining: 00:27:14
Wrote:   2953 chunks,   1476.50 MiB, 1.21% - Overall: 73.68 MiB/s - Recent: 74.29 MiB/s - time taken: 00:00:20 - ~time remaining: 00:27:03
Wrote:   3244 chunks,   1622.00 MiB, 1.33% - Overall: 73.59 MiB/s - Recent: 73.51 MiB/s - time taken: 00:00:22 - ~time remaining: 00:27:18
Wrote:   3537 chunks,   1768.50 MiB, 1.45% - Overall: 73.54 MiB/s - Recent: 72.05 MiB/s - time taken: 00:00:24 - ~time remaining: 00:27:49
Wrote:   3832 chunks,   1916.00 MiB, 1.57% - Overall: 73.54 MiB/s - Recent: 73.27 MiB/s - time taken: 00:00:26 - ~time remaining: 00:27:19
Wrote:   4122 chunks,   2061.00 MiB, 1.69% - Overall: 73.45 MiB/s - Recent: 72.31 MiB/s - time taken: 00:00:28 - ~time remaining: 00:27:39
Wrote:   4414 chunks,   2207.00 MiB, 1.81% - Overall: 73.42 MiB/s - Recent: 73.98 MiB/s - time taken: 00:00:30 - ~time remaining: 00:27:00
Wrote:   4704 chunks,   2352.00 MiB, 1.93% - Overall: 73.36 MiB/s - Recent: 72.81 MiB/s - time taken: 00:00:32 - ~time remaining: 00:27:24
Wrote:   4998 chunks,   2499.00 MiB, 2.05% - Overall: 73.36 MiB/s - Recent: 73.94 MiB/s - time taken: 00:00:34 - ~time remaining: 00:26:57

At the end of filling an SSD, you will see a major slowdown as reallocation stalls: