From c618f87cd2e96438468a391246d63ba1803f35c8 Mon Sep 17 00:00:00 2001 From: Matthew Ahrens Date: Fri, 10 Apr 2020 10:39:55 -0700 Subject: Add `zstream redup` command to convert deduplicated send streams Deduplicated send and receive is deprecated. To ease migration to the new dedup-send-less world, the commit adds a `zstream redup` utility to convert deduplicated send streams to normal streams, so that they can continue to be received indefinitely. The new `zstream` command also replaces the functionality of `zstreamdump`, by way of the `zstream dump` subcommand. The `zstreamdump` command is replaced by a shell script which invokes `zstream dump`. The way that `zstream redup` works under the hood is that as we read the send stream, we build up a hash table which maps from ` -> `. Whenever we see a WRITE record, we add a new entry to the hash table, which indicates where in the stream file to find the WRITE record for this block. (The key is `drr_toguid, drr_object, drr_offset`.) For entries other than WRITE_BYREF, we pass them through unchanged (except for the running checksum, which is recalculated). For WRITE_BYREF records, we change them to WRITE records. We find the referenced WRITE record by looking in the hash table (for the record with key `drr_refguid, drr_refobject, drr_refoffset`), and then reading the record header and payload from the specified offset in the stream file. This is why the stream can not be a pipe. The found WRITE record replaces the WRITE_BYREF record, with its `drr_toguid`, `drr_object`, and `drr_offset` fields changed to be the same as the WRITE_BYREF's (i.e. we are writing the same logical block, but with the data supplied by the previous WRITE record). This algorithm requires memory proportional to the number of WRITE records (same as `zfs send -D`), but the size per WRITE record is relatively low (40 bytes, vs. 72 for `zfs send -D`). A 1TB send stream with 8KB blocks (`recordsize=8k`) would use around 5GB of RAM to "redup". Reviewed-by: Jorgen Lundman Reviewed-by: Paul Dagnelie Reviewed-by: Brian Behlendorf Signed-off-by: Matthew Ahrens Closes #10124 Closes #10156 --- configure.ac | 1 + 1 file changed, 1 insertion(+) (limited to 'configure.ac') diff --git a/configure.ac b/configure.ac index 8604cdaa5..7522940d2 100644 --- a/configure.ac +++ b/configure.ac @@ -80,6 +80,7 @@ AC_CONFIG_FILES([ cmd/zhack/Makefile cmd/zinject/Makefile cmd/zpool/Makefile + cmd/zstream/Makefile cmd/zstreamdump/Makefile cmd/ztest/Makefile cmd/zvol_id/Makefile -- cgit v1.2.3