I'm not a Linux developer. I have no patches. But I'm a Linux admin, who very actively uses VDO for storage solutions. Zstd would be very useful in cases where more compression ratio is required. So this is just feedback from fields. Glad to know that this is on the roadmap. Thank you Matt ср, 22 янв. 2025 г. в 20:56, Matthew Sakai <msakai@xxxxxxxxxx>: > > > > On 1/22/25 4:35 AM, Anton Gavriliuk wrote: > > 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) > > We cannot remove support for lz4. There are existing users that rely on it. > > I have no objection to adding more options, though. It's on our roadmap > already, so perhaps we'll look into it. If you wanted to put together > patches for adding this, we'd certainly take a look at them. > > Matt > > > 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 > >>> > >> > > >
