For storage server solutions space saving is very useful, both compression and deduplication are important. Deduplication is just a part of the story. What if the compression algorithm (lz4 or zstd) could be selected per device basis with default lz4 ? It also may not be a bad idea to add compression levels from --fast to --best. Combining above, users could select different algorithms (lz4, zstd), different compression ratios and speed for each device. For instance - there are 2 volumes, one with hot data and lz4, another with cold data with zstd, but both volumes with deduplication. > Switching algorithms after data has been written to the volume could make older compressed data unreadable, so we don't want to allow that. Yes, there must be a warning, that after selecting the algorithm there is no turning back. An example - nearly a year ago, HPE's software defined storage solution - "Alletra MP" compression algorithm was switched to lz4 -> zstd. If still keeps a single compression algorithm, zstd almost always looks better lz4 (probably except decompress speed) Anton ср, 22 янв. 2025 г. в 04:59, Matthew Sakai <msakai@xxxxxxxxxx>: > > It's a reasonable idea. We've discussed it before but it hasn't been > particularly high priority. Since VDO is mainly focused on > deduplication, it's not clear how much it would help to use a different > compression algorithm, but it shouldn't hurt anything, either. > > To make this work we'd want to add a new create-time option to specify > the compression algorithm to use. Switching algorithms after data has > been written to the volume could make older compressed data unreadable, > so we don't want to allow that. > > Matt > > On 1/18/25 12:53 PM, Anton Gavriliuk wrote: > > What if zstd can be added to VDO as a compression algorithm along with lz4 ? > > > > It could provide more flexibility for users - faster compression or > > better compression ratio. > > > > Anton > > >
