Re: new database files not compressed

Nikolay Borisov
2020-08-31T12:57:51Z

On 31.08.20 г. 15:54 ч., Hamish Moffatt wrote:
> On 31/8/20 9:15 pm, Roman Mamedov wrote:
>> On Mon, 31 Aug 2020 18:53:54 +1000
>> Hamish Moffatt <hamish-btrfs@moffatt.email> wrote:
>>
>>> $ sudo mount -O compress-force=zstd /dev/sdb /mnt/test
>> Specifying the filesystem mount options is done with -o, not -O.
>> See "man mount".
>>
> Argh, I messed up the dd test. It does work for dd from /dev/zeroes when
> mounted properly. It still doesn't compress my Firebird files though.
>
>
> $ mount | grep btrfs
> /dev/sdb on /mnt/test type btrfs
> (rw,relatime,compress-force=zstd:3,space_cache,subvolid=5,subvol=/)
> $ dd if=/dev/zero of=zeroes bs=32k count=1024
> 1024+0 records in
> 1024+0 records out
> 33554432 bytes (34 MB, 32 MiB) copied, 0.0244041 s, 1.4 GB/s
> $ sudo compsize zeroes
> Type       Perc     Disk Usage   Uncompressed Referenced
> TOTAL        3%      1.0M          32M          32M
> zstd         3%      1.0M          32M          32M
> $ zcat ~/*.zip | gbak -REP -page 16384 stdin test2.fdb
> $ sudo compsize test2.fdb
> Type       Perc     Disk Usage   Uncompressed Referenced
> TOTAL      100%      194M         194M         191M
> none       100%      194M         194M         191M
> $ isql-fb
> Use CONNECT or CREATE DATABASE to specify a database
> SQL> create database 'test3.fdb' page_size 16384;
> SQL> ^D
> $ sudo compsize test3.fdb
> Type       Perc     Disk Usage   Uncompressed Referenced
> TOTAL      100%      2.2M         2.2M         2.2M
> none       100%      2.2M         2.2M         2.2M
>

This means the data being passed to btrfs is not compressible. I.e after
coompression the data is not smaller than the original, input data.

>
> Hamish
>