Thread: [PATCH] pg_upgrade: support for btrfs copy-on-write clones
Add file cloning as an alternative data transfer method to pg_upgrade.
Currently only btrfs is supported, but copy-on-write cloning is also
available on at least ZFS. Cloning must be requested explicitly and if
it isn't supported by the operating system or filesystem a fatal error
is thrown.
This provides upgrade performance similar to link mode while allowing
the old cluster to be used even after the new one has been started.
Signed-off-by: Oskari Saarenmaa <os@ohmu.fi>
---configure | 5 +-configure.in | 7 ++-contrib/pg_upgrade/check.c
| 3 +contrib/pg_upgrade/file.c | 125 +++++++++++++++++++++++++++++----------contrib/pg_upgrade/option.c |
7 +++contrib/pg_upgrade/pg_upgrade.h | 13 ++--contrib/pg_upgrade/relfilenode.c | 31
++++------doc/src/sgml/pgupgrade.sgml | 7 +++src/include/pg_config.h.in | 3 +9 files changed, 141
insertions(+),60 deletions(-)
diff --git a/configure b/configure
index c685ca3..5087463 100755
--- a/configure
+++ b/configure
@@ -10351,7 +10351,10 @@ done
-for ac_header in crypt.h dld.h fp_class.h getopt.h ieeefp.h ifaddrs.h langinfo.h poll.h pwd.h sys/ioctl.h sys/ipc.h
sys/poll.hsys/pstat.h sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/socket.h sys/sockio.h sys/tas.h sys/time.h
sys/un.htermios.h ucred.h utime.h wchar.h wctype.h
+for ac_header in crypt.h dld.h fp_class.h getopt.h ieeefp.h ifaddrs.h langinfo.h \
+ linux/btrfs.h poll.h pwd.h sys/ioctl.h sys/ipc.h sys/poll.h sys/pstat.h \
+ sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/socket.h sys/sockio.h \
+ sys/tas.h sys/time.h sys/un.h termios.h ucred.h utime.h wchar.h wctype.hdoas_ac_Header=`$as_echo
"ac_cv_header_$ac_header"| $as_tr_sh`if { as_var=$as_ac_Header; eval "test \"\${$as_var+set}\" = set"; }; then
diff --git a/configure.in b/configure.in
index 82771bd..609aa73 100644
--- a/configure.in
+++ b/configure.in
@@ -982,7 +982,12 @@ AC_SUBST(OSSP_UUID_LIBS)##dnl sys/socket.h is required by AC_FUNC_ACCEPT_ARGTYPES
-AC_CHECK_HEADERS([crypt.h dld.h fp_class.h getopt.h ieeefp.h ifaddrs.h langinfo.h poll.h pwd.h sys/ioctl.h sys/ipc.h
sys/poll.hsys/pstat.h sys/resource.h sys/select.h sys/sem.h sys/shm.h sys/socket.h sys/sockio.h sys/tas.h sys/time.h
sys/un.htermios.h ucred.h utime.h wchar.h wctype.h])
+AC_CHECK_HEADERS([crypt.h dld.h fp_class.h getopt.h ieeefp.h ifaddrs.h \
+ langinfo.h linux/btrfs.h poll.h pwd.h sys/ioctl.h \
+ sys/ipc.h sys/poll.h sys/pstat.h sys/resource.h \
+ sys/select.h sys/sem.h sys/shm.h sys/socket.h \
+ sys/sockio.h sys/tas.h sys/time.h sys/un.h termios.h \
+ ucred.h utime.h wchar.h wctype.h])# On BSD, test for net/if.h will fail unless sys/socket.h# is
includedfirst.
diff --git a/contrib/pg_upgrade/check.c b/contrib/pg_upgrade/check.c
index 0376fcb..2a52dd8 100644
--- a/contrib/pg_upgrade/check.c
+++ b/contrib/pg_upgrade/check.c
@@ -151,6 +151,9 @@ check_new_cluster(void) if (user_opts.transfer_mode == TRANSFER_MODE_LINK)
check_hard_link();
+ if (user_opts.transfer_mode == TRANSFER_MODE_CLONE)
+ check_clone_file();
+ check_is_super_user(&new_cluster); /*
diff --git a/contrib/pg_upgrade/file.c b/contrib/pg_upgrade/file.c
index dfeb79f..fc935b7 100644
--- a/contrib/pg_upgrade/file.c
+++ b/contrib/pg_upgrade/file.c
@@ -8,11 +8,16 @@ */#include "postgres_fe.h"
+#include "pg_config.h"#include "pg_upgrade.h"#include <fcntl.h>
+#ifdef HAVE_LINUX_BTRFS_H
+# include <sys/ioctl.h>
+# include <linux/btrfs.h>
+#endif#ifndef WIN32
@@ -23,21 +28,42 @@ static int win32_pghardlink(const char *src, const char *dst);/*
- * copyAndUpdateFile()
+ * upgradeFile() *
- * Copies a relation file from src to dst. If pageConverter is non-NULL, this function
- * uses that pageConverter to do a page-by-page conversion.
+ * Transfer a relation file from src to dst using one of the supported
+ * methods. If the on-disk format of the new cluster is bit-for-bit
+ * compatible with the on-disk format of the old cluster we can simply link
+ * each relation to perform a true in-place upgrade. Otherwise we must copy
+ * (either block-by-block or using a copy-on-write clone) the data from old
+ * cluster to new cluster and then perform the conversion. */const char *
-copyAndUpdateFile(pageCnvCtx *pageConverter,
- const char *src, const char *dst, bool force)
+upgradeFile(transferMode transfer_mode, const char *src,
+ const char *dst, pageCnvCtx *pageConverter){ if (pageConverter == NULL) {
- if (pg_copy_file(src, dst, force) == -1)
- return getErrorText(errno);
- else
- return NULL;
+ int rc = -1;
+
+ switch (transfer_mode)
+ {
+ case TRANSFER_MODE_COPY:
+ rc = pg_copy_file(src, dst, true);
+ break;
+ case TRANSFER_MODE_CLONE:
+ rc = upg_clone_file(src, dst);
+ break;
+ case TRANSFER_MODE_LINK:
+ rc = pg_link_file(src, dst);
+ break;
+ }
+
+ return (rc < 0) ? getErrorText(errno) : NULL;
+ }
+ else if (transfer_mode != TRANSFER_MODE_COPY)
+ {
+ return "Cannot in-place update this cluster, "
+ "page-by-page (copy-mode) conversion is required"; } else {
@@ -100,29 +126,6 @@ copyAndUpdateFile(pageCnvCtx *pageConverter,}
-/*
- * linkAndUpdateFile()
- *
- * Creates a hard link between the given relation files. We use
- * this function to perform a true in-place update. If the on-disk
- * format of the new cluster is bit-for-bit compatible with the on-disk
- * format of the old cluster, we can simply link each relation
- * instead of copying the data from the old cluster to the new cluster.
- */
-const char *
-linkAndUpdateFile(pageCnvCtx *pageConverter,
- const char *src, const char *dst)
-{
- if (pageConverter != NULL)
- return "Cannot in-place update this cluster, page-by-page conversion is required";
-
- if (pg_link_file(src, dst) == -1)
- return getErrorText(errno);
- else
- return NULL;
-}
-
-#ifndef WIN32static intcopy_file(const char *srcfile, const char *dstfile, bool force)
@@ -228,6 +231,64 @@ win32_pghardlink(const char *src, const char *dst)#endif
+int
+upg_clone_file(const char *existing_file, const char *new_file)
+{
+#ifdef BTRFS_IOC_CLONE
+ int rc, res_errno = 0, src_fd = -1, dest_fd = -1;
+
+ src_fd = open(existing_file, O_RDONLY);
+ if (src_fd < 0)
+ return -1;
+
+ dest_fd = open(new_file, O_RDWR | O_CREAT | O_EXCL, S_IRUSR | S_IWUSR);
+ if (dest_fd < 0)
+ {
+ close(src_fd);
+ return -1;
+ }
+
+ rc = ioctl(dest_fd, BTRFS_IOC_CLONE, src_fd);
+ if (rc < 0)
+ {
+ pg_log(PG_REPORT, "btrfs clone: %s\n", strerror(errno));
+ res_errno = errno; /* save errno for caller */
+ unlink(new_file);
+ }
+
+ close(dest_fd);
+ close(src_fd);
+
+ errno = res_errno; /* restore errno after close() calls */
+ return rc;
+#else
+ /* TODO: add support for zfs clones */
+ pg_log(PG_REPORT, "system does not support file cloning\n");
+ errno = ENOSYS;
+ return -1;
+#endif
+}
+
+void
+check_clone_file(void)
+{
+ char existing_file[MAXPGPATH];
+ char cloned_file[MAXPGPATH];
+
+ snprintf(existing_file, sizeof(existing_file), "%s/PG_VERSION", old_cluster.pgdata);
+ snprintf(cloned_file, sizeof(cloned_file), "%s/PG_VERSION.linktest", new_cluster.pgdata);
+ unlink(cloned_file); /* might fail */
+
+ if (upg_clone_file(existing_file, cloned_file) == -1)
+ {
+ pg_log(PG_FATAL,
+ "Could not clone a file between old and new data directories: %s\n"
+ "File cloning is currently only supported on btrfs.\n",
+ getErrorText(errno));
+ }
+ unlink(cloned_file);
+}
+/* fopen() file with no group/other permissions */FILE *fopen_priv(const char *path, const char *mode)
diff --git a/contrib/pg_upgrade/option.c b/contrib/pg_upgrade/option.c
index 2774b1e..fdf9f5c 100644
--- a/contrib/pg_upgrade/option.c
+++ b/contrib/pg_upgrade/option.c
@@ -54,6 +54,7 @@ parseCommandLine(int argc, char *argv[]) {"retain", no_argument, NULL, 'r'}, {"jobs",
required_argument,NULL, 'j'}, {"verbose", no_argument, NULL, 'v'},
+ {"clone", no_argument, NULL, 1}, {NULL, 0, NULL, 0} }; int option; /*
Commandline option */
@@ -186,6 +187,10 @@ parseCommandLine(int argc, char *argv[]) log_opts.verbose = true;
break;
+ case 1:
+ user_opts.transfer_mode = TRANSFER_MODE_CLONE;
+ break;
+ default: pg_log(PG_FATAL, "Try \"%s --help\" for more
information.\n",
@@ -236,6 +241,8 @@ Options:\n\ -D, --new-datadir=DATADIR new cluster data directory\n\ -j, --jobs
number of simultaneous processes or threads to use\n\ -k, --link link instead of copying files
tonew cluster\n\
+ --clone use copy-on-write cloning instead of copying\n\
+ files to new cluster (only supported on btrfs)\n\ -o, --old-options=OPTIONS old
clusteroptions to pass to the server\n\ -O, --new-options=OPTIONS new cluster options to pass to the server\n\
-p,--old-port=PORT old cluster port number (default %d)\n\
diff --git a/contrib/pg_upgrade/pg_upgrade.h b/contrib/pg_upgrade/pg_upgrade.h
index 0b3ad20..6932bd6 100644
--- a/contrib/pg_upgrade/pg_upgrade.h
+++ b/contrib/pg_upgrade/pg_upgrade.h
@@ -209,12 +209,13 @@ typedef struct} ControlData;/*
- * Enumeration to denote link modes
+ * Enumeration to denote transfer mode */typedef enum{ TRANSFER_MODE_COPY,
- TRANSFER_MODE_LINK
+ TRANSFER_MODE_LINK,
+ TRANSFER_MODE_CLONE} transferMode;/*
@@ -381,12 +382,12 @@ const pageCnvCtx *setupPageConverter(void);typedef void *pageCnvCtx;#endif
-const char *copyAndUpdateFile(pageCnvCtx *pageConverter, const char *src,
- const char *dst, bool force);
-const char *linkAndUpdateFile(pageCnvCtx *pageConverter, const char *src,
- const char *dst);
+const char *upgradeFile(transferMode transfer_mode, const char *src,
+ const char *dst, pageCnvCtx *pageConverter);void check_hard_link(void);
+void check_clone_file(void);
+int upg_clone_file(const char *old_file, const char *new_file);FILE *fopen_priv(const char *path, const
char*mode);/* function.c */
diff --git a/contrib/pg_upgrade/relfilenode.c b/contrib/pg_upgrade/relfilenode.c
index a951fc9..c808313 100644
--- a/contrib/pg_upgrade/relfilenode.c
+++ b/contrib/pg_upgrade/relfilenode.c
@@ -32,7 +32,10 @@ transfer_all_new_tablespaces(DbInfoArr *old_db_arr, DbInfoArr *new_db_arr,
char *old_pgdata, char *new_pgdata){ pg_log(PG_REPORT, "%s user relation files\n",
- user_opts.transfer_mode == TRANSFER_MODE_LINK ? "Linking" : "Copying");
+ user_opts.transfer_mode == TRANSFER_MODE_COPY ? "Copying" :
+ user_opts.transfer_mode == TRANSFER_MODE_LINK ? "Linking" :
+ user_opts.transfer_mode == TRANSFER_MODE_CLONE ? "Cloning" :
+ "FAIL"); /* * Transfering files by tablespace is tricky because a single database can
@@ -270,26 +273,14 @@ transfer_relfile(pageCnvCtx *pageConverter, FileNameMap *map, /* Copying files might take
sometime, so give feedback. */ pg_log(PG_STATUS, "%s", old_file);
- if ((user_opts.transfer_mode == TRANSFER_MODE_LINK) && (pageConverter != NULL))
- pg_log(PG_FATAL, "This upgrade requires page-by-page conversion, "
- "you must use copy mode instead of link mode.\n");
-
- if (user_opts.transfer_mode == TRANSFER_MODE_COPY)
- {
- pg_log(PG_VERBOSE, "copying \"%s\" to \"%s\"\n", old_file, new_file);
-
- if ((msg = copyAndUpdateFile(pageConverter, old_file, new_file, true)) != NULL)
- pg_log(PG_FATAL, "error while copying relation \"%s.%s\" (\"%s\" to \"%s\"): %s\n",
- map->nspname, map->relname, old_file, new_file, msg);
- }
- else
+ msg = upgradeFile(user_opts.transfer_mode, old_file, new_file, pageConverter);
+ if (msg != NULL) {
- pg_log(PG_VERBOSE, "linking \"%s\" to \"%s\"\n", old_file, new_file);
-
- if ((msg = linkAndUpdateFile(pageConverter, old_file, new_file)) != NULL)
- pg_log(PG_FATAL,
- "error while creating link for relation \"%s.%s\" (\"%s\" to \"%s\"): %s\n",
- map->nspname, map->relname, old_file, new_file, msg);
+ pg_log(PG_FATAL, "error while %s relation \"%s.%s\" (\"%s\" to \"%s\"): %s\n",
+ (user_opts.transfer_mode == TRANSFER_MODE_COPY ? "copying" :
+ user_opts.transfer_mode == TRANSFER_MODE_LINK ? "linking" :
+ user_opts.transfer_mode == TRANSFER_MODE_CLONE ? "cloning" :
+ "FAIL"), map->nspname, map->relname, old_file, new_file, msg); } }
diff --git a/doc/src/sgml/pgupgrade.sgml b/doc/src/sgml/pgupgrade.sgml
index f6cd9f0..fc9b89d 100644
--- a/doc/src/sgml/pgupgrade.sgml
+++ b/doc/src/sgml/pgupgrade.sgml
@@ -126,6 +126,13 @@ </varlistentry> <varlistentry>
+ <term><option>--clone</option></term>
+ <listitem><para>use copy-on-write clones instead of copying or hard linking files to
+ the new cluster; this option can only be used when the old and new clusters reside
+ on the same btrfs filesystem</para></listitem>
+ </varlistentry>
+
+ <varlistentry> <term><option>-o</option> <replaceable class="parameter">options</replaceable></term>
<term><option>--old-options</option><replaceable class="parameter">options</replaceable></term>
<listitem><para>optionsto be passed directly to the
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 8aabf3c..7cd5a8d 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -317,6 +317,9 @@/* Define to 1 if you have the `z' library (-lz). */#undef HAVE_LIBZ
+/* Define to 1 if you have the <linux/btrfs.h> header file. */
+#undef HAVE_LINUX_BTRFS_H
+/* Define to 1 if constants of type 'long long int' should have the suffix LL. */#undef HAVE_LL_CONSTANTS
--
1.8.3.1
Oskari Saarenmaa <os@ohmu.fi> wrote: > Add file cloning as an alternative data transfer method to pg_upgrade. > Currently only btrfs is supported, but copy-on-write cloning is also > available on at least ZFS. Cloning must be requested explicitly and if > it isn't supported by the operating system or filesystem a fatal error > is thrown. > > This provides upgrade performance similar to link mode while allowing > the old cluster to be used even after the new one has been started. Please add the patch here to make sure it gets reviewed: https://commitfest.postgresql.org/action/commitfest_view/open For more information on the process, see: http://wiki.postgresql.org/wiki/CommitFest -- Kevin Grittner EDB: http://www.enterprisedb.com The Enterprise PostgreSQL Company
On 10/01/2013 06:31 PM, Oskari Saarenmaa wrote: > Add file cloning as an alternative data transfer method to pg_upgrade. > Currently only btrfs is supported, but copy-on-write cloning is also > available on at least ZFS. Cloning must be requested explicitly and if > it isn't supported by the operating system or filesystem a fatal error > is thrown. > So, just curious, why isn't ZFS supported? It's what I am more interested in, at least. cheers andrew
On 02/10/13 17:18, Andrew Dunstan wrote: > > On 10/01/2013 06:31 PM, Oskari Saarenmaa wrote: >> Add file cloning as an alternative data transfer method to pg_upgrade. >> Currently only btrfs is supported, but copy-on-write cloning is also >> available on at least ZFS. Cloning must be requested explicitly and if >> it isn't supported by the operating system or filesystem a fatal error >> is thrown. >> > > So, just curious, why isn't ZFS supported? It's what I am more > interested in, at least. No fundamental reason; I'm hoping ZFS will be supported in addition to btrfs, but I don't have any systems with ZFS filesystems at the moment so I haven't been able to test it or find out the mechanisms ZFS uses for cloning. On btrfs cloning is implemented with a custom btrfs-specific ioctl, ZFS probably has something similar which would be pretty easy to add on top of this patch. Added this patch to commitfest as suggested, https://commitfest.postgresql.org/action/patch_view?id=1251 / Oskari
On Wed, Oct 2, 2013 at 05:23:31PM +0300, Oskari Saarenmaa wrote: > On 02/10/13 17:18, Andrew Dunstan wrote: > > > >On 10/01/2013 06:31 PM, Oskari Saarenmaa wrote: > >>Add file cloning as an alternative data transfer method to pg_upgrade. > >>Currently only btrfs is supported, but copy-on-write cloning is also > >>available on at least ZFS. Cloning must be requested explicitly and if > >>it isn't supported by the operating system or filesystem a fatal error > >>is thrown. > >> > > > >So, just curious, why isn't ZFS supported? It's what I am more > >interested in, at least. > > No fundamental reason; I'm hoping ZFS will be supported in addition > to btrfs, but I don't have any systems with ZFS filesystems at the > moment so I haven't been able to test it or find out the mechanisms > ZFS uses for cloning. On btrfs cloning is implemented with a custom > btrfs-specific ioctl, ZFS probably has something similar which would > be pretty easy to add on top of this patch. > > Added this patch to commitfest as suggested, > https://commitfest.postgresql.org/action/patch_view?id=1251 What is the performance overhead of using a cloned data directory for a cluster? -- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. +
> No fundamental reason; I'm hoping ZFS will be supported in addition to > btrfs, but I don't have any systems with ZFS filesystems at the moment > so I haven't been able to test it or find out the mechanisms ZFS uses > for cloning. On btrfs cloning is implemented with a custom > btrfs-specific ioctl, ZFS probably has something similar which would be > pretty easy to add on top of this patch. Would you like a VM with ZFS on it? I'm pretty sure I can supply one. -- Josh Berkus PostgreSQL Experts Inc. http://pgexperts.com
On 2013-10-02 17:32, Josh Berkus wrote: >> No fundamental reason; I'm hoping ZFS will be supported in addition to >> btrfs, but I don't have any systems with ZFS filesystems at the moment >> so I haven't been able to test it or find out the mechanisms ZFS uses >> for cloning. On btrfs cloning is implemented with a custom >> btrfs-specific ioctl, ZFS probably has something similar which would >> be >> pretty easy to add on top of this patch. > > Would you like a VM with ZFS on it? I'm pretty sure I can supply one. > > -- > Josh Berkus > PostgreSQL Experts Inc. > http://pgexperts.com I can also supply SSH access to a FreeBSD 10 system that is totally ZFS. -- Larry Rosenman http://www.lerctr.org/~ler Phone: +1 214-642-9640 (c) E-Mail: ler@lerctr.org US Mail: 108 Turvey Cove, Hutto, TX 78634-5688
03.10.2013 01:35, Larry Rosenman kirjoitti: > On 2013-10-02 17:32, Josh Berkus wrote: >>> No fundamental reason; I'm hoping ZFS will be supported in addition to >>> btrfs, but I don't have any systems with ZFS filesystems at the moment >>> so I haven't been able to test it or find out the mechanisms ZFS uses >>> for cloning. On btrfs cloning is implemented with a custom >>> btrfs-specific ioctl, ZFS probably has something similar which would be >>> pretty easy to add on top of this patch. >> >> Would you like a VM with ZFS on it? I'm pretty sure I can supply one. >> > I can also supply SSH access to a FreeBSD 10 system that is totally ZFS. Thanks for the offers, but it looks like ZFS doesn't actually implement a similar file level clone operation. See https://github.com/zfsonlinux/zfs/issues/405 for discussion on a feature request for it. ZFS does support cloning entire datasets which seem to be similar to btrfs subvolume snapshots and could be used to set up a new data directory for a new $PGDATA. This would require the original $PGDATA to be a dataset/subvolume of its own and quite a bit different logic (than just another file copy method in pg_upgrade) to initialize the new version's $PGDATA as a snapshot/clone of the original. The way this would work is that the original $PGDATA dataset/subvolume gets cloned to a new location after which we move the files out of the way of the new PG installation and run pg_upgrade in link mode. I'm not sure if there's a good way to integrate this into pg_upgrade or if it's just something that could be documented as a fast way to run pg_upgrade without touching original files. With btrfs tooling the sequence would be something like this: btrfs subvolume snapshot /srv/pg92 /srv/pg93 mv /srv/pg93/data /srv/pg93/data92 initdb /data/pg93/data pg_upgrade --link\ --old-datadir=/data/pg93/data92 \ --new-datadir=/data/pg93/data / Oskari
On Fri, Oct 4, 2013 at 10:42:46PM +0300, Oskari Saarenmaa wrote: > Thanks for the offers, but it looks like ZFS doesn't actually implement > a similar file level clone operation. See > https://github.com/zfsonlinux/zfs/issues/405 for discussion on a feature > request for it. > > ZFS does support cloning entire datasets which seem to be similar to > btrfs subvolume snapshots and could be used to set up a new data > directory for a new $PGDATA. This would require the original $PGDATA > to be a dataset/subvolume of its own and quite a bit different logic > (than just another file copy method in pg_upgrade) to initialize the new > version's $PGDATA as a snapshot/clone of the original. The way this > would work is that the original $PGDATA dataset/subvolume gets cloned to > a new location after which we move the files out of the way of the new > PG installation and run pg_upgrade in link mode. I'm not sure if > there's a good way to integrate this into pg_upgrade or if it's just > something that could be documented as a fast way to run pg_upgrade > without touching original files. > > With btrfs tooling the sequence would be something like this: > > btrfs subvolume snapshot /srv/pg92 /srv/pg93 > mv /srv/pg93/data /srv/pg93/data92 > initdb /data/pg93/data > pg_upgrade --link \ > --old-datadir=/data/pg93/data92 \ > --new-datadir=/data/pg93/data Does btrfs support file system snapshots? If so, shouldn't people just take a snapshot of the old data directory before the ugprade, rather than using cloning? -- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. +
05.10.2013 16:38, Bruce Momjian kirjoitti: > On Fri, Oct 4, 2013 at 10:42:46PM +0300, Oskari Saarenmaa wrote: >> Thanks for the offers, but it looks like ZFS doesn't actually implement >> a similar file level clone operation. See >> https://github.com/zfsonlinux/zfs/issues/405 for discussion on a feature >> request for it. >> >> ZFS does support cloning entire datasets which seem to be similar to >> btrfs subvolume snapshots and could be used to set up a new data >> directory for a new $PGDATA. This would require the original $PGDATA >> to be a dataset/subvolume of its own and quite a bit different logic >> (than just another file copy method in pg_upgrade) to initialize the new >> version's $PGDATA as a snapshot/clone of the original. The way this >> would work is that the original $PGDATA dataset/subvolume gets cloned to >> a new location after which we move the files out of the way of the new >> PG installation and run pg_upgrade in link mode. I'm not sure if >> there's a good way to integrate this into pg_upgrade or if it's just >> something that could be documented as a fast way to run pg_upgrade >> without touching original files. >> >> With btrfs tooling the sequence would be something like this: >> >> btrfs subvolume snapshot /srv/pg92 /srv/pg93 >> mv /srv/pg93/data /srv/pg93/data92 >> initdb /data/pg93/data >> pg_upgrade --link \ >> --old-datadir=/data/pg93/data92 \ >> --new-datadir=/data/pg93/data > > Does btrfs support file system snapshots? If so, shouldn't people just > take a snapshot of the old data directory before the ugprade, rather > than using cloning? Yeah, it's possible to clone an existing subvolume, but this requires that $PGDATA is a subvolume of its own and would be a bit difficult to integrate into existing pg_upgrade scripts. The BTRFS_IOC_CLONE ioctl operates on file level and can be used to clone files anywhere in a btrfs filesystem. / Oskari
On 05.10.2013 16:57, Oskari Saarenmaa wrote: > 05.10.2013 16:38, Bruce Momjian kirjoitti: >> On Fri, Oct 4, 2013 at 10:42:46PM +0300, Oskari Saarenmaa wrote: >>> Thanks for the offers, but it looks like ZFS doesn't actually implement >>> a similar file level clone operation. See >>> https://github.com/zfsonlinux/zfs/issues/405 for discussion on a feature >>> request for it. >>> >>> ZFS does support cloning entire datasets which seem to be similar to >>> btrfs subvolume snapshots and could be used to set up a new data >>> directory for a new $PGDATA. This would require the original $PGDATA >>> to be a dataset/subvolume of its own and quite a bit different logic >>> (than just another file copy method in pg_upgrade) to initialize the new >>> version's $PGDATA as a snapshot/clone of the original. The way this >>> would work is that the original $PGDATA dataset/subvolume gets cloned to >>> a new location after which we move the files out of the way of the new >>> PG installation and run pg_upgrade in link mode. I'm not sure if >>> there's a good way to integrate this into pg_upgrade or if it's just >>> something that could be documented as a fast way to run pg_upgrade >>> without touching original files. >>> >>> With btrfs tooling the sequence would be something like this: >>> >>> btrfs subvolume snapshot /srv/pg92 /srv/pg93 >>> mv /srv/pg93/data /srv/pg93/data92 >>> initdb /data/pg93/data >>> pg_upgrade --link \ >>> --old-datadir=/data/pg93/data92 \ >>> --new-datadir=/data/pg93/data >> >> Does btrfs support file system snapshots? If so, shouldn't people just >> take a snapshot of the old data directory before the ugprade, rather >> than using cloning? > > Yeah, it's possible to clone an existing subvolume, but this requires > that $PGDATA is a subvolume of its own and would be a bit difficult to > integrate into existing pg_upgrade scripts. > > The BTRFS_IOC_CLONE ioctl operates on file level and can be used to > clone files anywhere in a btrfs filesystem. Hmm, you can also do cp --reflog -r data92 data-tmp pg_upgrade --link --old-datadir=data92-copy --new-datadir=data-tmp rm -rf data-tmp That BTRFS_IOC_CLONE ioctl seems so hacky that I'd rather not get that in our source tree. cp --reflog is much more likely to get that magic incantation right, since it gets a lot more attention and testing than pg_upgrade. I'm not in favor of adding filesystem-specific tricks into pg_upgrade. It would be nice to list these tricks in the docs, though. - Heikki
On Fri, Nov 15, 2013 at 10:40:20AM +0200, Heikki Linnakangas wrote: > >The BTRFS_IOC_CLONE ioctl operates on file level and can be used to > >clone files anywhere in a btrfs filesystem. > > Hmm, you can also do > > cp --reflog -r data92 data-tmp I think you mean --reflink here. > pg_upgrade --link --old-datadir=data92-copy --new-datadir=data-tmp > rm -rf data-tmp > > That BTRFS_IOC_CLONE ioctl seems so hacky that I'd rather not get > that in our source tree. cp --reflog is much more likely to get that > magic incantation right, since it gets a lot more attention and > testing than pg_upgrade. > > I'm not in favor of adding filesystem-specific tricks into > pg_upgrade. It would be nice to list these tricks in the docs, > though. I have applied the attached patch which suggests the use of file system snapshots and copy-on-write file copies. -- Bruce Momjian <bruce@momjian.us> http://momjian.us EnterpriseDB http://enterprisedb.com + Everyone has their own god. +