On Jan 9, 2020, at 9:27 AM, Stefan Kooman <ste...@bit.nl<mailto:ste...@bit.nl>> wrote:
Quoting Kyriazis, George (george.kyria...@intel.com<mailto:george.kyria...@intel.com>): On Jan 9, 2020, at 8:00 AM, Stefan Kooman <ste...@bit.nl<mailto:ste...@bit.nl>> wrote: Quoting Kyriazis, George (george.kyria...@intel.com<mailto:george.kyria...@intel.com>): The source pool has mainly big files, but there are quite a few smaller (<4KB) files that I’m afraid will create waste if I create the destination zpool with ashift > 12 (>4K blocks). I am not sure, though, if ZFS will actually write big files in consecutive blocks (through a send/receive), so maybe the blocking factor is not the actual file size, but rather the zfs block size. I am planning on using zfs gzip-9 compression on the destination pool, if it matters. You might want to consider Zstandard for compression: https://engineering.fb.com/core-data/smaller-and-faster-data-compression-with-zstandard/ Thanks for the pointer. Sorry, I am not sure how you are suggesting to using zstd, since it’s not part of the standard zfs compression algorithms. It's in FreeBSD ... and should be in ZOL soon: https://github.com/zfsonlinux/zfs/pull/9735 FreeNAS is based on FreeBSD, so it will make it there…. eventually. But compression is not my problem, I have enough horsepower to deal with gzip-9. It’s not the bottlenneck. Ceph file I/O is. You can optimize a ZFS fs to use larger blocks for those files that are small ... and use large block sizes for other fs ... if it's easy to split them. From what I understand, zfs uses a single block per file, if files are <4K, ie. It does not put 2 small files in a single block. How would larger blocks help small files? Also, as far as I know ashift is a pool property, set only at pool creation. Hmm, I meant you can use large block size for the large files and small block size for the small files. Sure, but how to do that. As far as I know block size is a property of the pool, not a single file. Thanks! George I don’t have control over the original files and how they are stored in the source server. These are user’s files. Then you somehow need to find a middle ground. Gr. Stefan -- | BIT BV https://www.bit.nl/ Kamer van Koophandel 09090351 | GPG: 0xD14839C6 +31 318 648 688 / i...@bit.nl<mailto:i...@bit.nl>
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