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author | delphij <delphij@FreeBSD.org> | 2014-03-19 23:55:03 +0000 |
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committer | delphij <delphij@FreeBSD.org> | 2014-03-19 23:55:03 +0000 |
commit | ede49d4106ad9e6d34a2592322e48604f72605bd (patch) | |
tree | 0012bcb04d95eaf4e65ed2f983e9d51d47236888 /cddl/contrib/opensolaris/cmd/zpool | |
parent | 8e41bb96f82aa123d5f4c625c68f95b253640b28 (diff) | |
download | FreeBSD-src-ede49d4106ad9e6d34a2592322e48604f72605bd.zip FreeBSD-src-ede49d4106ad9e6d34a2592322e48604f72605bd.tar.gz |
MFC r260150: MFV r259170:
4370 avoid transmitting holes during zfs send
4371 DMU code clean up
illumos/illumos-gate@43466aae47bfcd2ad9bf501faec8e75c08095e4f
NOTE: Make sure the boot code is updated if a zpool upgrade is
done on boot zpool.
Diffstat (limited to 'cddl/contrib/opensolaris/cmd/zpool')
-rw-r--r-- | cddl/contrib/opensolaris/cmd/zpool/zpool-features.7 | 72 |
1 files changed, 71 insertions, 1 deletions
diff --git a/cddl/contrib/opensolaris/cmd/zpool/zpool-features.7 b/cddl/contrib/opensolaris/cmd/zpool/zpool-features.7 index d807257..43eede5 100644 --- a/cddl/contrib/opensolaris/cmd/zpool/zpool-features.7 +++ b/cddl/contrib/opensolaris/cmd/zpool/zpool-features.7 @@ -23,7 +23,7 @@ .\" .\" $FreeBSD$ .\" -.Dd October 08, 2013 +.Dd December 31, 2013 .Dt ZPOOL-FEATURES 7 .Os .Sh NAME @@ -286,6 +286,76 @@ and will be returned to the .Sy enabled state when all datasets that use this feature are destroyed. +.It Sy enabled_txg +.Bl -column "READ\-ONLY COMPATIBLE" "com.delphix:enabled_txg" +.It GUID Ta com.delphix:enabled_txg +.It READ\-ONLY COMPATIBLE Ta yes +.It DEPENDENCIES Ta none +.El +.Pp +Once this feature is enabled ZFS records the transaction group number +in which new features are enabled. This has no user-visible impact, +but other features may depend on this feature. +.Pp +This feature becomes +.Sy active +as soon as it is enabled and will +never return to being +.Sy enabled . +.It Sy hole_birth +.Bl -column "READ\-ONLY COMPATIBLE" "com.delphix:hole_birth" +.It GUID Ta com.delphix:hole_birth +.It READ\-ONLY COMPATIBLE Ta no +.It DEPENDENCIES Ta enabled_txg +.El +.Pp +This feature improves performance of incremental sends +.Pq Dq zfs send -i +and receives for objects with many holes. +The most common case of +hole-filled objects is zvols. +.Pp +An incremental send stream from snapshot +.Sy A +to snapshot +.Sy B +contains information about every block that changed between +.Sy A +and +.Sy B . +Blocks which did not change between those snapshots can be +identified and omitted from the stream using a piece of metadata called +the 'block birth time', but birth times are not recorded for holes +.Pq blocks filled only with zeroes . +Since holes created after +.Sy A +cannot be +distinguished from holes created before +.Sy A , +information about every +hole in the entire filesystem or zvol is included in the send stream. +.Pp +For workloads where holes are rare this is not a problem. +However, when +incrementally replicating filesystems or zvols with many holes +.Pq for example a zvol formatted with another filesystem +a lot of time will +be spent sending and receiving unnecessary information about holes that +already exist on the receiving side. +.Pp +Once the +.Sy hole_birth +feature has been enabled the block birth times +of all new holes will be recorded. +Incremental sends between snapshots +created after this feature is enabled will use this new metadata to avoid +sending information about holes that already exist on the receiving side. +.Pp +This feature becomes +.Sy active +as soon as it is enabled and will +never return to being +.Sy enabled . .El .Sh SEE ALSO .Xr zpool 8 |