ACFS DB" Oracle ACFS and Oracle Database: a Perfect Marriage

BASLE BERN BRUGG DÜSSELDORF FRANKFURT A.M. FREIBURG I.BR. GENEVA
HAMBURG COPENHAGEN LAUSANNE MUNICH STUTTGART VIENNA ZURICH
Oracle ACFS and Oracle Database:
a Perfect Marriage?
Ludovico Caldara
Senior Consultant @ Trivadis
Oracle ACE

About Ludovico Caldara
Oracle ACFS and Oracle Database: a Perfect Marriage?2 04.09.2015
■ 16 Years DBA (Not Only Oracle)
▪ I do it everywhere (even Windows)
■ RAC ATTACK Ninja & co-writer
■ VP, SOUG & ITOUG Board member
■ OCP (11g, 12c, MySQL) & OCE
■ Italian living in Switzerland
■ http://www.ludovicocaldara.net
■ @ludodba
■ ludovicocaldara
Opinions are my own

Our company.
Trivadis is a market leader in IT consulting, system integration, solution engineering
and the provision of IT services focusing on and technologies
in Switzerland, Germany, Austria and Denmark. We offer our services in the following
strategic business fields:
Trivadis Services takes over the interactive operation of your IT systems.
O P E R A T I O N

COPENHAGEN
MUNICH
LAUSANNE
BERN
ZURICH
BRUGG
GENEVA
HAMBURG
DÜSSELDORF
FRANKFURT
STUTTGART
FREIBURG
BASLE
VIENNA
With over 600 specialists and IT experts in your region.
14 Trivadis branches and more than
600 employees
200 Service Level Agreements
Over 4,000 training participants
Research and development budget:
CHF 5.0 / EUR 4 million
Financially self-supporting and
sustainably profitable
Experience from more than 1,900
projects per year at over 800
customers

ASM, ADVM, ACFS?

ASM, ADVM, ACFS?
ASM
Disk Group 1 Disk Group 2
ADVM Vol2
ACFS /app
.exe.dbf.txt
DB03
Disk Group 3
.dbf
.ctl
.dbf
.dbf
.dbf
.ctl
.dbf
.dbf
DB04APP01
ADVM Vol4ADVM Vol3
Ext4 /abc
.exe.dbf.txt
APP02 APP02
RAW

Cluster File System – ACFS (1)
Needs Grid Infrastructure!
ASM Cluster File System (ACFS) is a general purpose cluster filesystem implemented as part of ASM
– Dynamic loadable OS drivers delivered by Oracle
– Based on ASM Dynamic Volume Manager (ADVM)
Supports both traditional UNIX-style file access control classes and file access control lists (ACLs) for
Windows platforms
Uses standard file related system calls – no need to use special tools
Cannot be used for Grid Infrastructure home, voting files, OCR, ASM diag dest.
04.09.2015 Oracle ACFS and Oracle Database: a Perfect Marriage?7

ASM Cluster File System (ACFS) leverages ASM
– High performance (Variable extents-based allocation)
– Data spread evenly across ASM disks
– Same data protection ot the Disk Group (External / Normal / High redundancy)
Supports Database Homes and Database diag dests
Multi-node, shared filesystem

Main features: Snapshots, Encryption, Security, Replication, Auditing
Up to 11.2.0.3, it was part of the Cloud File System option ($$)
Starting with 11.2.0.4, ACFS and ADVM are no more an extra-cost option
Starting with 12cR1, Oracle ACFS supports Oracle Datafiles if DB release >= 11.2.0.4
– https://docs.oracle.com/database/121/OSTMG/asmfilesystem.htm#OSTMG95961
Since ODA sw version 12.1.2, databases are created on ACFS

Datafiles on ACFS

ASM, ADVM, ACFS?
ASM
ADVM Vol2
ACFS /app
.exe.dbf.txt
DB03
Disk Group 3
.dbf
.ctl
.dbf
.dbf
.dbf
.ctl
.dbf
.dbf
DB04APP01
ADVM Vol4ADVM Vol3
Ext4 /abc
.exe.dbf.txt
APP02 APP02
RAW

ASM, ADVM, ACFS?
ASM
ADVM Vol1 ADVM Vol2
ACFS /u02 ACFS /app
.ctl.dbf.dbf
.exe.dbf.txt
DB01 DB03
Disk Group 3
.dbf
.ctl
.dbf
.dbf
.dbf
.ctl
.dbf
.dbf
DB04APP01
ADVM Vol4ADVM Vol3
Ext4 /abc
.exe.dbf.txt
APP02 APP02
RAW

ASM, ADVM, ACFS?
ASM
ADVM Vol1 ADVM Vol2
ACFS /u02 ACFS /app
.ctl.dbf.dbf
.exe.dbf.txt
DB01 DB03
Disk Group 3
.dbf
.ctl
.dbf
.dbf
.dbf
.ctl
.dbf
.dbf
DB04APP01
ADVM Vol4ADVM Vol3
Ext4 /abc
.exe.dbf.txt
APP02 APP02
RAW
NEW: 12c

Requirements
No Oracle Restart, only Grid Infrastructure (even single-node, but cluster installation)
advm.compatible and asm.compatible must be >= 12.1
Volume stripe columns must be set to 1 in 12.1.0.1.
– From 12.1.0.2 onwards the default is ok (columns 8, width 1024kb)
The DB must be running with filesystemio_options=setall
If Grid Infrastructure 12.1.0.1, only Unix/Linux
– Starting with 12.1.0.2, also Windows

Implementation steps (1)
## create the Disk Group with compatible 12.1
cat dg_acfs.xml
<dg name="ACFS" redundancy="external">
<dsk string="ORCL:DISK5" /><dsk string="ORCL:DISK6" /><dsk string="ORCL:DISK7" /><dsk string="ORCL:DISK8" />
<a name="compatible.asm" value="12.1.0.0.0"/>
<a name="compatible.rdbms" value="12.1.0.0.0"/>
<a name="compatible.advm" value="12.1.0.0.0"/>
</dg>

cat dg_acfs.xml
</dg>
asmcmd mkdg dg_acfs.xml

cat dg_acfs.xml
</dg>
## create the Volume (stripe columns must be set to 1 in 12.1.0.1. From 12.1.0.2 onwards the default is ok)
asmcmd volcreate -G acfs -s 19G volacfs --column 1

cat dg_acfs.xml
</dg>
## create the Volume (stripe columns must be set to 1 in 12.1.0.1. From 12.1.0.2 onwards the default is ok)
asmcmd volcreate -G acfs -s 19G volacfs --column 1
asmcmd volinfo --all
Diskgroup Name: ACFS
Volume Name: VOLACFS
Volume Device: /dev/asm/volacfs-167
State: ENABLED
Size (MB): 19456
Resize Unit (MB): 8
Redundancy: UNPROT
Stripe Columns: 1
...

grid@racvagn1:~/ $ /sbin/mkfs -t acfs /dev/asm/volacfs-167
mkfs.acfs: version = 12.1.0.2.0
mkfs.acfs: on-disk version = 39.0
mkfs.acfs: volume = /dev/asm/volacfs-167
mkfs.acfs: volume size = 20401094656 ( 19.00 GB )
mkfs.acfs: Format complete.

grid@racvagn1:~/ $ sudo su -
# srvctl add filesystem -d /dev/asm/volacfs-167 -m /u02 -u oracle -fstype ACFS -autostart ALWAYS

# srvctl start filesystem -d /dev/asm/volacfs-167
# df -k /u02
Filesystem 1K-blocks Used Available Use% Mounted on
/dev/asm/volacfs-167 19922944 117616 19805328 1% /u02

# df -k /u02
/dev/asm/volacfs-167 19922944 117616 19805328 1% /u02
# chown oracle:oinstall /u02
# chmod 775 /u02
# su - oracle
oracle@racvagn1:~/ [+ASM1] mkdir -p /u02/app/oracle/oradata

# df -k /u02
/dev/asm/volacfs-167 19922944 117616 19805328 1% /u02
# chmod 775 /u02
# su - oracle
oracle@racvagn1:~/ [+ASM1] crsctl stat res ora.acfs.volacfs.acfs -t
Name Target State Server State details
Local Resources
ora.acfs.volacfs.acfs
ONLINE ONLINE racvagn1 mounted on /u02,STABLE

# df -k /u02
/dev/asm/volacfs-167 19922944 117616 19805328 1% /u02
# chmod 775 /u02
# su - oracle
oracle@racvagn1:~/ [+ASM1] crsctl stat res ora.acfs.volacfs.acfs -t
Name Target State Server State details
Local Resources
ora.acfs.volacfs.acfs
... Then create the database there... With filesystemio_options=setall!!

ASM is the default, but the
ACFS filesystem is discovered
And proposed by default
when Storage Type “File System” is selected
DBCA

Performance

SLOBing ASM vs ACFS
Environment
– ACFS filesystem, ASM DiskGroup
– Same topology, one SSD disk, same environment
– Same database and tablespace, datafile moved online from ASM to ACFS between runs
SQL> alter database move datafile 2 to
'/u02/ACFSDB/ACFSDB/datafile/slob01.dbf';
Database altered.
OWNER TABLE_NAME NUM_ROWS BLOCKS
---------- ---------- ---------------- ----------------
USER2 CF1 97,464 100,493
USER1 CF1 100,000 100,883

SLOBing ASM vs ACFS
5 SLOB runs on ACFS, 5 SLOB runs on ASM
– Instance caging (1CPU)
– 20% update, no Hot Blocks
– consider only 1-bk reads/second
on SLOB TBSP
– skip worst, average others

SLOBing ASM vs ACFS
5 SLOB runs on ACFS, 5 SLOB runs on ASM
– Instance caging (1CPU)
– 20% update, no Hot Blocks
– consider only 1-bk reads/second
on SLOB TBSP
– skip worst, average others
Best ACFS run worse than worst ASM run
– Average loss: 3,8%
0
500
1000
1500
2000
2500
3000
3500
4000
1 2 3 4
ASM vs ACFS
ASM ACFS

SLOBing ASM vs ACFS
I did different tests (different update pcts, run durations, etc.), almost same results
Not a big performance loss, but... not so good either!
These are non-exhaustive tests, maybe ACFS has better (or worse!) performances
under different loads.
Anyway, due to additional layer, ACFS cannot be faster than flat ASM in any case

Magic features
(or options?)

ACFS and Datafiles - Features
For Database files:
– ACFS Snapshots require Enterprise Edition

ACFS and Datafiles - Features
For Database files:
– ACFS Snapshots require Enterprise Edition
– ACFS Encryption, ACFS Security, ACFS Replication, ACFS Auditing are not available.
Oracle Database options should be used instead. Respectively: Oracle Advanced
Security, Oracle Database Vault, Oracle Data Guard, Oracle Audit Vault)
– https://docs.oracle.com/database/121/DBLIC/editions.htm#CIHDDJCJ

So "Datafiles on ACFS"
is about snapshots
(remember, EE only)

0
500
1000
1500
2000
2500
3000
3500
4000
1 2 3 4
0
2
4
8
16
Write performance w/ snapshots (on base mountpoint)
snapshots
SLOB Run
IOs/second

0
500
1000
1500
2000
2500
3000
3500
4000
1 2 3 4
0
2
4
8
16
Write performance w/ snapshots (on base mountpoint)
snapshots
SLOB Run
IOs/second Big regression starting with the first snapshot.
No further regressions when more inactive snapshots are created.

Copy on Write?

Copy on Write?
Somebody calls it Redirect on Write.

Copy on Write?
0x1000000 0x2000000 0x3000000
0x1000000
0x2000000
0x3000000
inode
/mp/file

Copy on Write?
0x1000000 0x2000000 0x3000000
0x1000000
0x2000000
0x3000000
inode
/mp/file Modify a block in first extent of /mp/file?

Copy on Write?
0x1000000 0x2000000 0x3000000
0x1000000
0x2000000
0x3000000
inode
No snapshots point to the same extent: OK

Writes on base FS with snapshots
What if I have snapshots?
0x1000000 0x2000000 0x3000000
0x1000000
0x2000000
0x3000000
inode
/mp/file
0x1000000
0x2000000
0x3000000
inode
/mp/../sp1
/file
0x1000000
0x2000000
0x3000000
inode
/mp/../sp2
/file

0x1000000 0x2000000 0x3000000
0x1000000
0x2000000
0x3000000
inode
/mp/file
0x1000000
0x2000000
0x3000000
inode
/mp/../sp1
/file
0x1000000
0x2000000
0x3000000
inode
/mp/../sp2
/file
Modify a block in first extent of /mp/file?

0x1000000 0x2000000 0x3000000
0x1000000
0x2000000
0x3000000
inode
/mp/file
Snapshots point to the same extent: Redirect
0x4000000
0x1000000
0x2000000
0x3000000
inode
/mp/../sp1
/file
0x1000000
0x2000000
0x3000000
inode
/mp/../sp2
/file
0x4000000

0x1000000 0x2000000 0x3000000
0x1000000
0x2000000
0x3000000
inode
/mp/file
0x4000000
0x1000000
0x2000000
0x3000000
inode
/mp/../sp1
/file
0x1000000
0x2000000
0x3000000
inode
/mp/../sp2
/file
0x4000000
Next write on the same block: OK

0x1000000 0x2000000 0x3000000
0x1000000
0x2000000
0x3000000
inode
/mp/file
0x4000000
0x1000000
0x2000000
0x3000000
inode
/mp/../sp1
/file
0x1000000
0x2000000
0x3000000
inode
/mp/../sp2
/file
0x4000000
Modify a block in first extent of snapshot 1?

0x1000000 0x2000000 0x3000000
0x1000000
0x2000000
0x3000000
inode
/mp/file
0x4000000
0x1000000
0x2000000
0x3000000
inode
/mp/../sp1
/file
0x1000000
0x2000000
0x3000000
inode
/mp/../sp2
/file
0x4000000
0x5000000
0x5000000
Snapshot 2 points to the same extent: Redirect

0x1000000 0x2000000 0x3000000
0x1000000
0x2000000
0x3000000
inode
/mp/file
0x4000000
0x1000000
0x2000000
0x3000000
inode
/mp/../sp1
/file
0x1000000
0x2000000
0x3000000
inode
/mp/../sp2
/file
0x4000000
0x5000000
0x5000000

0x1000000 0x2000000 0x3000000
0x1000000
0x2000000
0x3000000
inode
/mp/file
0x4000000
0x1000000
0x2000000
0x3000000
inode
/mp/../sp1
/file
0x1000000
0x2000000
0x3000000
inode
/mp/../sp2
/file
0x4000000
0x5000000
0x5000000
Modify a block in first extent of snapshot 2 is
also ok because no snaps point to the same extent

Evidence?

Evidence of Redirect on Write Snapshot
# acfsutil snap create -w SNAP1 /u02
acfsutil snap create: Snapshot operation is complete.
# acfsutil snap create -w -p SNAP1 SNAP2 /u02
acfsutil snap create: Snapshot operation is complete.
Then, two nested snapshots: /u01 <- SNAP1 <- SNAP2
# dd if=/dev/urandom of=/u02/test/file count=16 bs=1048576
16+0 records in
16+0 records out
16777216 bytes (17 MB) copied, 2.83643 s, 5.9 MB/s
First, let’s create a file 16MB big

# acfsutil info file /u02/test/file | grep |
--offset ----length | -dev --------offset
0 6524928 | 1 30975586304
6524928 5156864 | 1 30982111232
11681792 7925760 | 1 30987268096
# acfsutil info file /u02/.ACFS/snaps/SNAP1/test/file | grep |
0 6524928 | 1 30975586304
6524928 5156864 | 1 30982111232
11681792 7925760 | 1 30987268096
0 6524928 | 1 30975586304
6524928 5156864 | 1 30982111232
11681792 7925760 | 1 30987268096
All three files (base and snapshots) use the same extents

# dd if=/dev/urandom of=/u02/test/file count=1 bs=8192 conv=notrunc
1+0 records in
1+0 records out
8192 bytes (8.2 kB) copied, 0.068746 s, 119 kB/s
0 6524928 | 1 310378496 (was 30975586304)
6524928 5156864 | 1 30982111232
11681792 7925760 | 1 30987268096
0 6524928 | 1 30975586304
6524928 5156864 | 1 30982111232
11681792 7925760 | 1 30987268096
0 6524928 | 1 30975586304
6524928 5156864 | 1 30982111232
11681792 7925760 | 1 30987268096
If I modify 8k in the first extent of /u02/test/file, the whole extent of the base file is redirected
Redirecting the whole extent. This is why the write is slower. Not because of a double write
typical of Copy on Write

# dd if=/dev/urandom of=/u02/test/file count=1 bs=8192 conv=notrunc seek=1
1+0 records in
1+0 records out
8192 bytes (8.2 kB) copied, 0.00299343 s, 2.7 MB/s
0 6524928 | 1 310378496
6524928 5156864 | 1 30982111232
11681792 7925760 | 1 30987268096
0 6524928 | 1 30975586304
6524928 5156864 | 1 30982111232
11681792 7925760 | 1 30987268096
0 6524928 | 1 30975586304
6524928 5156864 | 1 30982111232
11681792 7925760 | 1 30987268096
Modifying another 8k block on the same extent does not lead to relocation. Write is faster.

# dd if=/dev/urandom of=/u02/.ACFS/snaps/SNAP2/test/file count=1 bs=8192 conv=notrunc seek=1
1+0 records in
1+0 records out
8192 bytes (8.2 kB) copied, 0.0348603 s, 235 kB/s
0 6524928 | 1 310378496
6524928 5156864 | 1 30982111232
11681792 7925760 | 1 30987268096
0 6524928 | 1 30975586304
6524928 5156864 | 1 30982111232
11681792 7925760 | 1 30987268096
0 6524928 | 1 316903424 (was 30975586304)
6524928 5156864 | 1 30982111232
11681792 7925760 | 1 30987268096
The same would have appened mofiying snapshot 1.
Another try: modifying 8k in the first extent of second snapshot file leads to redirect for snapshot 2

Snapshot size and Write Latency Avg are correlated
Snapshot Size
IO Latency
Snap size=
DB Size
Same
Latency w/o
Snapshot
Curves depend on the repartition of hot spots / cold spots into the extents
New Snapshots == New latency spikes
Snap
Create

Other considerations about performances
ACFS is variable-extent based
– It may incur in fragmentation, especially with snapshots (due to extents redirects)
– I do not have elements for saying if it is a major problem or not
– [acfsdefrag0] system process exists, let me guess what it is for
– One extent may reside on different ASM Allocation Units (see acfsutil info file –d)
– Size allocated and size used may differ
## 1 MB file extent lean on two AUs on disks ASMDISK3 and ASMDISK6
----current offset | -cur vol offset -mir --extent --device name --------doffset --length -ASMdev
0 | 30397808640 0 3622 ORCL:ASMDISK3 5074698240 409600 5
409600 | 30398218240 0 3623 ORCL:ASMDISK6 5090836480 638976 1
--------------------------------------------------------------------------------------------------

Database on ACFS:
snapshot usecases

Snapshots are useful for...
Backup LOL, just kidding
Getting a consistent point before a modification
– Alternative to RESTORE POINTs?
Datafile copy for fast media recovery
Database cloning for Q&A, reporting, other
Multitenant: create pdb from pdb snapshot copy

Snapshots for consistent copy

On most snapshot technologies
– You take a snapshot
– You modify the data
– In case of problems, you revert (restore) the snapshot
With ACFS, there is still no way to revert a snapshot natively (no acfsutil command or other)
Nowadays, it does not make sense!

Workaround 1: Manual datafile copy from the snapshot
– shutdown
– delete the content from the base FS
– move the files from the snapshot
– drop/recreate the snapshot (to free up used snapshot space)
– startup

Workaround 2: Do some magic with RMAN and a temporary snapshot
– create a writable snapshot from snapshot
– shutdown
– delete the content from the base FS
– RMAN catalog start with... switch database to copy
– startup
– move back the datafiles with online move, then get the rid of the temporary snapshot

Workaround 3: Use guaranteed restore points instead of snapshots.
– :-P

File copy for fast media recovery

Follow the same procedure explained before...
– new writable snapshot form snapshot
– offline datafile
– catalog file, switch datafile to copy
– recover datafile, online datafile
– move datafile to old location (thank you 12c!)
– delete temporary snapshot

Having snapshots catalogued in RMAN as datafile copies allows also other kinds of
recovery
– E.g. block recovery

Database cloning for Q&A,
reporting, other

ACFS for Database cloning
Space efficient, fast-created copies
Source should not be performance-critical
ASM
Disk Group 1
ADVM Vol2
ACFS
/u02
.dbf
DB
.dbf.dbf
SNAP1
/u02/…/
SNAP2
/u02/…/
SNAP3
/u02/…/
SNAP4
/u02/…/
.dbf.dbf.dbf
.dbf.dbf.dbf
.dbf.dbf.dbf
.dbf.dbf.dbf
DB01 DB02 DB03 DB04

ACFS for Database cloning – better with DG
Do not use with SYNC redo transport. If you need protection, setup a second standby.
ASM
Disk Group 1
ADVM Vol2
ACFS
/u02
.dbf
STDBY
.dbf.dbf
SNAP1
/u02/…/
SNAP2
/u02/…/
SNAP3
/u02/…/
SNAP4
/u02/…/
.dbf.dbf.dbf
.dbf.dbf.dbf
.dbf.dbf.dbf
.dbf.dbf.dbf
DB01 DB02 DB03 DB04
ASM
Disk Group 1
.dbf.dbf.dbf
DB

Best approach for cloning a standby on the same host
DGMGRL> edit database ACFSDB set state="APPLY-OFF";
$ acfsutil snap create -w CLONE /u02
DGMGRL> edit database ACFSDB set state="APPLY-ON";
SOURCE SQL> Backup controlfile to trace as '...' reuse resetlogs;
SOURCE SQL> create pfile='...' from spfile;
... sed-modify controlfile and pfile
CLONE SQL> create spfile from pfile ='...';
CLONE SQL> create controlfile …
CLONE SQL> alter database open resetlogs;
CLONE SQL> alter tablespace TEMP add tempfile ...;
CLONE SQL> shutdown immediate;
CLONE SQL> startup mount exclusive;
# nid TARGET=SYS DBNAME=CLONE
$ srvctl add database –db CLONE –oh $ORACLE_HOME –spfile=/u02/.ACFS/snaps/CLONE/.../ ...

Advantages of DG + ACFS
No need to recover datafiles, no fuzzy datafiles
– Stopping the redo apply on a standby database leaves the datafiles recovered to a
point in time
– Subsequent «alter database open resetlogs» just works
Decoupled disks, no impact on source database (primary)
DEMO?

gDBClone.pl
gDBClone.pl
http://www.oracle.com/technetwork/indexes/samplecode/gdbclone-download-2295388.html
Not production ready
Give a look into the source code. It does not look as something written by a DBA…
– Shuts down the source (but requires it in archivelog mode)
– Get the lists of datafiles for CREATE CONTROLFILE by doing a ls -l of /…/datafiles/

Create Pluggable Database
Snapshot Copy

Create Pluggable Database Snapshot Copy
If you use Multitenant, you can thin copy a PDB from another one, inside the same CDB:
SQL> create pluggable database CLONE1 from SOURCE snapshot copy;
Pluggable database created.

Create Pluggable Database Snapshot Copy
Internally:
– it creates the snapshot on ACFS
– It copies the definition of the PDB using the same datafiles
– It replaces the datafiles in file$ directly with symlinks pointing to the snapshot
Cloning inside multitenant means consolidating per business line, not per environment.

Ludovico Caldara
Senior Consultant
ludovico.caldara@trivadis.com

ACFS DB" Oracle ACFS and Oracle Database: a Perfect Marriage

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