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 Mic92 | https://github.com/Mic92/niks3 | 18:19:54 |
| Mic92 | Testing this now for two weeks in production. | 18:20:15 |
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 @linus:schreibt.jetzt | In reply to @julienmalka:matrix.org
Do we have measures of the total deduplication of an attic cache ? attic doesn't currently have a built-in command for it but it should be pretty easy to get from the db | 08:51:14 |
| @linus:schreibt.jetzt | attic=# select sum(file_size) / (select sum(nar_size) from nar) from chunk;
?column?
------------------------
0.20098691256561418637
(1 row)
| 08:52:57 |
| @linus:schreibt.jetzt | so I guess I'm using 20% as much storage for nars as I would be without dedup | 08:53:15 |
| @linus:schreibt.jetzt | *and compression | 08:53:30 |
| @linus:schreibt.jetzt | of course that isn't entirely representative of how much space the cache takes up including file metadata and the database | 08:54:44 |
| @linus:schreibt.jetzt | but I think nars would be the bulk of my binary cache, so that's already a useful number ^^ | 08:55:09 |
 Julien | Given the state of things with AWS hosting it would be interesting to see how much of that dedup we could benefit from in the cache.nixos.org binary cache without asking for demesurate computationnal stress to the server | 08:55:07 |
| @linus:schreibt.jetzt | yeah | 08:55:57 |
| @linus:schreibt.jetzt | I know some people were interested in looking into options there, do you know if anyone's actually doing anything on that front? | 08:56:25 |
| Julien | To be honnest I thought that that was what people were doing on the group but I was only following the conversation from afar. I’m interested into doing experiments on that field though. | 08:57:40 |
| @linus:schreibt.jetzt | I guess raitobezarius is the most likely to know :D | 08:58:26 |
 @elvishjerricco:matrix.org | Linux Hackerman: Any suggestion on special_small_blocks value? I was thinking 8K since anything <=8K is worst case space efficiency on raidz2 (ashift=12) | 09:04:45 |
| Julien | In reply to @linus:schreibt.jetzt
attic=# select sum(file_size) / (select sum(nar_size) from nar) from chunk;
?column?
------------------------
0.20098691256561418637
(1 row)
On my own attic deployment I get 0.17052771681498935 | 09:04:49 |
| @linus:schreibt.jetzt | In reply to @elvishjerricco:matrix.org
Linux Hackerman: Any suggestion on special_small_blocks value? I was thinking 8K since anything <=8K is worst case space efficiency on raidz2 (ashift=12) sounds reasonable, and I don't think many narinfos will be bigger than 8K | 09:05:31 |
| @elvishjerricco:matrix.org | plus I think optane has 512B sectors, so ashift=9 on that vdev 😎 | 09:05:39 |
| @linus:schreibt.jetzt | but are you going to use raidz2 on your special too? | 09:05:39 |
| @elvishjerricco:matrix.org | you can't use raidz on special I'm pretty sure | 09:05:53 |
| @elvishjerricco:matrix.org | ashift=9 on the special just means that small things get even smaller | 09:06:41 |
