If a crash occurs, the next time a fileset in the domain is mounted,
the completed log transactions are replayed to disk and incomplete transactions
are backed out so that the original metadata on disk is restored.
These log
transactions, by default, save only metadata, not the data written to the
file.
This means that file sizes and locations on disk are consistent but,
depending on when the crash occurred, the user data from recent writes might
be out of date.
This is a trade-off for the increased throughput gained using
this method.
4.4.2 Asynchronous Atomic-Write Data Logging I/O
Asynchronous atomic-write data logging I/O is similar to asynchronous
I/O except that the data written to the buffer cache is also written to the
log file for each write request.
This
If a crash occurs, the data is recovered from the log file when the
fileset is remounted.
As in asynchronous I/O, all completed log transactions
are replayed and incomplete transactions are backed out.
Unlike asynchronous
I/O, however, the user's data has been written to the log, so both the metadata
and the data intended for the file can be restored.
This guarantees that each
8 KB increment of a write is either completely written to disk or is not written
to disk.
Because only completed write requests are processed, obsolete, possibly
sensitive data located where the system was about to write at the time of
the crash can never be accessed.
Disk writes in the wrong order, which might
cause inconsistencies in the event of a crash, can never occur.
Another way to prevent access to obsolete data is to use the
There are two types of atomic-write data logging: persistent and temporary.
Persistent logging sets an on-disk flag for a file so atomic-write data logging
persists across mounts and unmounts.
Temporary data logging sets an in-memory
flag activating atomic-write data logging for all files in the fileset for
the duration of the mount.
To turn persistent atomic-write data logging I/O on and off, use the
If a file has a frag, persistent atomic-write data logging cannot be
activated.
To activate data logging on a file that has a frag, do one of the
following:
Activate temporary atomic-write data logging, which operates
on files with frags.
Choose the
If you disable frag files by using the
Append enough bytes to the file to bring it up to the next
8 KB boundary.
For example, if
Files that use persistent atomic-write data logging cannot be memory
mapped through the
Use the
Any application that has the file open can call the
Files using temporary atomic-write data logging can be memory mapped.
Temporary atomic-write data logging is suspended until the last thread using
the memory-mapped file unmaps it.
In addition, files that have frags can use
temporary data logging feature.
NFS mounting does not affect logging behavior.
Synchronous I/O is similar to asynchronous I/O, but the data is written
both to the cache and to the disk before the write request returns to the
calling application.
This means that if a write is successful, the data is
guaranteed to be on disk.
Synchronous I/O reduces throughput because the write
does not return until after the I/O is complete.
In addition, since the application,
not the file system, determines when the data needs to be flushed to disk,
the likelihood of consolidating I/Os might be reduced if synchronous write
requests are small.
To turn synchronous I/O off and on, use the
You cannot use both the
You can activate temporary atomic-write data logging for the fileset
by using the
Caching improves performance when data is reused frequently.
AdvFS uses
a dynamic memory cache called the
By using the UBC for caching, AdvFS can maintain file data in memory
as long as memory is available.
If other system resources require some of
the memory in use by the file system cache, the UBC can reclaim the memory
that is needed.
Because AdvFS uses the UBC to control caching, the cache is tuned with
the UBC tunable parameters.
These include:
Variables that modify the maximum percentage of physical memory
that the UBC can use at one time
The percentage of pages that must be dirty before the UBC
starts writing them to disk
The maximum amount of memory allocated to the UBC that can
be used to cache a single file
See
System Configuration and Tuning
for guidelines for modifying these parameters.
Although caching data is the default and generally improves file system
performance, in some situations an application can increase throughput by
bypassing the data cache (see
Section 4.6).
Although direct I/O handles requests of any byte size, you get the best
performance when the requested transfer size is aligned on a disk sector boundary
and the transfer size is an even multiple of the underlying sector size (currently
512 bytes).
Direct I/O is particularly suited for files that are used exclusively
by a database.
However, if an application tends to access data multiple times,
direct I/O can adversely impact performance because caching does not occur.
When you specify direct I/O, it takes precedence and any data already in the
buffer cache for that file is automatically flushed to disk.
To open a file for direct I/O, use the
Regardless of the previous mode, the new mode is direct I/O and remains
so until the last close of the file.
Note that direct I/O, atomic-write data
logging, and memory mapping are mutually exclusive modes.
Therefore, if the
file is already open for atomic-write data logging or is memory mapped, then
calling the
The
You can change a number of attributes to improve system performance.
System Configuration and Tuning
details the significance of each attribute and the trade-offs engendered when
they are changed.
See
Increase the dirty-data caching threshold
Dirty or modified data is data that was written by an application and
cached but is not yet been written to disk.
You can modify the amount of
Modifying this variable by using the
Promote continuous I/O by using the
The
Change the I/O transfer size
AdvFS reads and writes data by 8 KB pages.
The maximum transfer size
is determined by the device driver and depends on the underlying storage configuration
but is typically 128 or 256 blocks.
LSM might assign a larger maximum transfer
size.
You can adjust the maximum transfer size by using the
Flush modified memory-mapped pages
The
Increase the memory available for access structures
AdvFS allocates file access structures until the percentage of pageable
memory used for the access structures reaches
The AdvFS file system attempts to store file data in contiguous blocks
on a disk.
This collection of contiguous blocks is called a file extent.
If
all data in a file is stored in contiguous blocks, that file has one file
extent.
However, as files grow, contiguous blocks on the disk might not be
available to accommodate the new data, and the system spreads the file over
discontiguous blocks.
As a result, the file is fragmented on the disk and
consists of multiple file extents.
File fragmentation degrades the read/write
performance because many disk addresses must be examined to access a file.
The
Files might be moved to other volumes in the defragmentation of a multivolume
domain.
You cannot control the placement of files during defragmentation,
but you can use the
You can improve the efficiency of the defragment process by deleting
any unneeded files in the domain before running the
It is difficult to specify the load that defragmenting places on a system.
The time it takes to defragment a domain depends on:
The size of the volume(s)
The amount of free space available
The activity of the system
The configuration of your domain
Because the
To defragment a domain, use the SysMan Manage an AdvFS Domain utility,
a graphical user interface (see
Appendix D), or enter the
The following restrictions apply to running the
You must have root user privileges.
All filesets in the domain must be mounted.
If you try to
defragment an active domain that includes unmounted filesets, an error message
is displayed.
A minimum free space of 1% of the total space or 5 MB per
volume (whichever is less) must be available to defragment each volume.
The
See
Run the
To determine the amount of fragmentation in your domain without starting
the utility, run the
The level of fragmentation you should allow in your file system before
running the utility depends on the size of the files and the number of extents.
This is largely application dependent, so monitor the number of extents to
see if elevated extent counts correlate with decreased application performance.
In many cases, even a large, fairly fragmented file does not show a noticeable
decrease in performance because of fragmentation.
It is not necessary to run
the
If your file system has been untouched for a month or two, that is,
if you did not run full periodic backups nor regularly reference your whole
file system, it is a good idea to run the
Running the
If you have a system, such as a mail server, that contains files that
are mostly smaller than 8 KB, run the
If you find that one file shows high fragmentation, you can defragment
that file (see
Section 4.9).
If you have the hardware resources and AdvFS Utilities, you can add
a volume by using the
The following example looks at the fragmentation of the
Information displayed before each pass and at the conclusion of the
defragmentation process indicates the amount of improvement made to the domain.
A decrease in the
To determine the amount of fragmentation level of a single file, run
the
To reduce the fragmentation of a file:
Use the
Back up and restore a file.
This tends to defragment it.
Back up the file by using the
Delete or rename the file.
Restore the data by using the
The
Files are moved from one volume to another, as illustrated in
Figure 4-1, until the percentage of used space on each volume
in the domain is as equal as possible.
Because the
To redistribute files across volumes, use the SysMan Manage an AdvFS
Domain utility, a graphical user interface (see
Appendix D), or
enter the
If you interrupt the balance process, all relocated files remain at
their new locations.
The rest of the files remain in their original locations.
The following restrictions apply to running the
You must have root user privileges.
All filesets in the domain must be mounted.
If you try to
balance an active domain that includes unmounted filesets, an error message
is displayed.
The
See
Use the
Use the
In the following example, the multivolume domain
If you suspect that a fileset or domain is straining system resources,
run the
To move a domain and its fileset to a new volume:
Make a new domain on the new device.
It must have a temporary
new name.
Create a fileset with the same name as the old.
Create a temporary mount-point directory for the fileset.
Mount the new fileset on the temporary mount point.
Use the
Unmount the old and new filesets.
Rename the new domain to the old name.
Since you have not
changed the domain and fileset names, it is not necessary to edit the
Mount the new fileset using the mount point of the old fileset.
The directory tree is then unchanged.
Delete the temporary mount-point directory.
If you have more than one fileset in your domain, follow steps two through
eight for each fileset.
If you are running operating system software Version 5.0 or later, the new
domain is created with the new DVN of 4 (see
Section 1.6.3).
However, if you must retain the DVN of 3 in order to use earlier versions
of the operating system, see
The following example moves the domain
If you have the optional AdvFS Utilities, you can use the
To move an entire file to a specific volume, use the
A file that is migrated is defragmented in the process if possible.
This means that you can use the
The following restrictions apply to the
You must have root user privilege.
You can perform only one migrate operation at a time on the
same file.
When you migrate a striped file, you can migrate from only
one volume at a time.
The
Choose the
Choose the
You can use the
The following example displays the extent map of a file called
The
You can
Use AdvFS striping only on directly attached storage that does not include
LSM, RAID, or a SAN.
Combining AdvFS striping with system striping might interfere
with optimal placement and cause system degradation.
The AdvFS
The form of the stripe command is:
To stripe a file:
Create a new, empty file.
If you do not create an empty file, the following error message is displayed:
Stripe it across the number of volumes desired.
Copy the data from the original file to the striped file.
Delete the original file and rename the striped file, if desired.
As the file is appended, AdvFS determines the number of pages per stripe
segment; the segments alternate among the disks in a sequential pattern.
For
example, the file system allocates the first segment of a two-disk striped
file on the first disk and the next segment on the second disk.
This completes
one sequence, or stripe.
The next stripe starts on the first disk, and so
on.
Because AdvFS spreads the I/O of the striped file across the specified
disks, the sequential read/write performance of the file increases.
You cannot use the
You cannot use AdvFS stripe utility on the
Before you use the
Using AdvFS striping when system-wide striping is in effect might degrade
performance.
The following example creates an empty file,
You can alter the pattern of striping in your domain by:
Removing striping from a file
Copy the striped file to a file that is not striped.
Delete the original.
Removing a striped volume
If you remove a volume that contains an AdvFS stripe segment, the
The
0 - Create crash dumps for no domains.
1 - Create crash dumps only for domains with mounted
filesets (default).
2 - Create crash dumps for all domains.
3 - Promote the domain panic to a system panic.
The
system crashes.
See
chfsets -o objectsafety
command (see
Section 1.7.10).
Choosing object safety prevents an application from reusing old data, but
it does not guarantee complete data recovery.
4.4.2.1 Persistent Atomic-Write Data Logging
fcntl()
function or enter the
chfile -L
command:
chfile -L on
file_name
chfile -L off
file_name
nofrag
option for the fileset
when you access it by using the
mkfset
or
chfsets
command.
chfsets -o nofrag
command, files with existing frags do not change.
You can, however, copy
a file with frags, delete the original file, and rename the copy to the original
file name.
The file is then free of frag files (see
Section 4.2).
fileb
has 6803 bytes, it
is stored in one 7 KB frag.
To activate data logging, you can add 1389 bytes
so the file terminates on an 8 KB boundary:
# dd if=/dev/zero of=fileb bs=1 seek=6803 \
count=1389 conv=notrunc
mmap
system call.
See
Section 5.5
for information on conflicting file usage.
4.4.2.2 Temporary Atomic-Write Data Logging
mount -o adl
command to set an in-memory
flag that activates temporary atomic-write data logging in a fileset for the
duration of the mount.
Persistent atomic-write data logging commands take
precedence over temporary commands while the file is open.
fcntl()
function to turn off temporary atomic-write data logging, or use
the
chfile -L off
command to turn off persistent atomic-write
data logging while the file is open.
All applications that have the file open
are affected.
After all applications close the file, temporary atomic-write
data logging is restored for the file.
You can check atomic-write data logging
status for a file by using the
chfile
command.
4.4.3 Synchronous I/O
O_SYNC
or
O_DSYNC
flag to the
open()
system
call (see the
Programmer's Guide).
To force all applications
to use synchronous I/O even if files are not opened in that mode, enter the
chfile -l
command:
chfile -l on
file_name
chfile -l off
file_name
4.4.4 Synchronous Atomic-Write Data Logging I/O
-l
and
-L
options of the
chfile
command to set synchronous atomic-write
data logging.
However, if you activate persistent atomic-write data logging
on a file by using the
chfile -L on
command, you can open
the file for synchronous I/O by using the
O_SYNC
or
O_DSYNC
flag to the
open()
system call (see the
Programmer's Guide).
mount -o adl, sync
command.
4.5 Data Cache Tuning
4.6 Improving Data Transfer Rate with Direct I/O
open()
function
and specify the
O_DIRECTIO
flag.
For example, for
file_x
enter:
open (file_x, O_DIRECTIO|O_RDWR, 0644)
open
function to initiate direct I/O fails.
fcntl()
function can be used to determine whether
the file is open in cached or in direct I/O mode.
See
fcntl(2)
and
open(2),
or the
Programmer's Guide
for more information.
4.7 Changing Attributes to Improve System Performance
sysconfig(8)
for more information.
You can modify
attributes to:
chvol -t
command or, for all new
volumes of a file system, by using the
AdvfsReadyQLim
attribute
(see
chvol(8)).
chvol
command
is most effective if smooth sync is disabled.
If your system is using smooth
sync (the default), then the rate at which the dirty data is flushed to disk
is best tuned by using the
smoothsync_age
attribute.
smoothsync_age
attribute
smoothsync_age
attribute specifies the number
of seconds that a modified page stays in the buffer cache before being flushed
to disk.
This allows the file system to balance the need to flush modified
pages to disk in a timely manner with the benefits of keeping the page in
memory while all modifications are being made.
chvol
command with the
-r
(read) or
-w
(write) options (see
chvol(8)).
AdvfsSyncMmapPages
attribute controls whether
modified memory-mapped pages are flushed to disk during a
sync
system call.
AdvfsAccessMaxPercent.
Increasing the value of the
AdvfsAccessMaxPercent
attribute might improve AdvFS performance on systems that open and reuse many
files, but this decreases the memory available for the virtual memory subsystem
and the Unified Buffer Cache (UBC).
Decreasing the value of the attribute
frees pageable memory but might degrade AdvFS performance on systems that
open and reuse many files.
defragment
utility reduces the amount of file
fragmentation in a domain by attempting to make the files more contiguous
so that the number of file extents is reduced.
In addition, defragmenting
a domain often makes the free space on a disk more contiguous so files that
are created later are also less fragmented.
showfile
to identify where a file is
stored.
If you want to move a file, use the
migrate
command
(see
Section 4.12).
defragment
utility.
Aborting the defragment process does not damage the file system.
Files that have been defragmented remain in their new locations.
defragment
utility creates a thread per
volume (up to a maximum of 20 threads), a domain consisting of several small
volumes is faster to defragment than one consisting of a large volume.
Multiple
threads might exact a severe performance penalty for ongoing I/O.
If you want
to limit defragmentation to a single thread (similar to Version 4 operating
system software behavior), use the
defragment -N 1
command.
defragment
command from the command line:
defragment
domain_name
defragment
command:
defragment
utility cannot be run while
the
addvol,
rmvol,
balance, or
rmfset
command is running in the same domain.
defragment(8)
for more information.
4.8.1 Choosing to Defragment
defragment
utility on your domain when you
experience performance degradation and then only when file system activity
is low.
defragment -v -n
command.
If the average
number of extents or the number of extents per file with extents is high or
the aggregate I/O performance is low, defragmentation might be helpful.
defragment
command on a system that is not experiencing
performance-related problems because of excessive file fragmentation.
verify
command
before you run the
defragment
command.
Run the
verify
command when there is low file system activity.
balance
utility before you run
defragment
might speed up the defragmentation process.
defragment
command
only when the output of the
showfile -x /mntpt/.tags/1
command indicates that the frag file is highly fragmented.
Here
/mntpt
is the mount point for the fileset and
.tags/1
is the frag file.
4.8.2 Defragmenting Example
addvol
command then remove the previous
volume by using the
rmvol
command.
Removing the volume
migrates the domain to the new volume, and the files in it are defragmented
as part of the migration.
accounts_domain
domain and at the number of extents in the
orig_file_1
file, and then defragments the domain for a maximum of 15 minutes.
Verbose mode is used to display the fragmentation data at the beginning of
each pass through the domain and at the end of the defragmentation process.
# defragment -vn accounts_domain
defragment: Gathering data for 'accounts_domain'
Current domain data:
Extents: 263675
Files w/ extents: 152693
Avg exts per file w/exts: 1.73
Aggregate I/O perf: 70%
Free space fragments: 85574
<100K <1M <10M >10M
Free space: 34% 45% 19% 2%
Fragments: 76197 8930 440 7
# showfile -x orig_file_1
Id Vol PgSz Pages XtntType Segs SegSz I/O Perf File
6.8002 2 16 71 simple ** ** async 82% orig_file_1
\\: 1
pageOff pageCnt vol volBlock blockCnt
0 5 2 40720 80
5 12 2 41856 192
17 16 2 40992 256
33 7 2 42048 112
40 12 2 41360 192
52 15 2 42160 240
67 4 2 41792 64
extentCnt: 7
# defragment -v -t 15 accounts_domain
defragment: Defragmenting domain 'accounts_domain'
Pass 1;
Volume 2: area at block 144 ( 130800 blocks): 0% full
Volume 1: area at block 468064 ( 539008 blocks): 49% full
Domain data as of the start of this pass:
Extents: 7717
Files w/extents: 6436
Avg exts per file w/exts: 1.20
Aggregate I/O perf: 78%
Free space fragments: 904
<100K <1M <10M >10M
Free space: 4% 5% 12% 79%
Fragments: 825 60 13 6
Pass 2;
Volume 1: area at block 924288 ( 547504 blocks): 69% full
Volume 2: area at block 144 ( 130800 blocks): 0% full
Domain data as of the start of this pass:
Extents: 6507
Files w/extents: 6436
Avg exts per file w/exts: 1.01
Aggregate I/O perf: 86%
Free space fragments: 1752
<100K <1M <10M >10M
Free space: 8% 13% 11% 67%
Fragments: 1574 157 15 6
Pass 3;
Domain data as of the start of this pass:
Extents: 6485
Files w/extents: 6436
Avg exts per file w/exts: 1.01
Aggregate I/O perf: 99%
Free space fragments: 710
<100K <1M <10M >10M
Free space: 3% 11% 21% 65%
Fragments: 546 126 32 6
Defragment: Defragmented domain 'accounts_domain'
Extents
and
Avg exts per file
w/extents
values indicates a reduction in file fragmentation.
An
increase in the
Aggregate I/O perf
value indicates improvement
in the overall efficiency of file-extent allocation.
4.9 Defragmenting a File
showfile -x
command to show the extents in the file.
(You might already have this information from examining the output of the
defragment -v -n
command.)
migrate
utility to move the file
to the same or a different volume containing adequate contiguous free space.
vdump
command.
vrestore
command.
4.10 Balancing a Multivolume Domain
balance
utility distributes the percentage of
used space evenly between volumes in a multivolume domain created with the
optional AdvFS Utilities.
This improves performance and evens the distribution
of future file allocations.
Figure 4-1: Balancing a Domain
balance
utility does not generally split files, domains with very large files might
not balance as evenly as domains with smaller files.
balance
command from the command line:
balance
domain_name
balance
utility:
balance
utility cannot run while the
addvol,
rmvol,
defragment,
or
rmfset
command is running in the same domain.
balance(8)
for more information.
4.10.1 Choosing to Balance
showfdmn
command to display domain information.
Look at the
% Used
field to determine if the files are
evenly distributed.
balance
utility to even file distribution
after you have added a volume by using the
addvol
command
or removed a volume by using the
rmvol
command (if there
are multiple volumes remaining).
4.10.2 Balance Example
usr_domain
is not balanced.
Volume 1 has 63% used space while volume 2, a
smaller volume, has 0% used space (it has just been added).
After balancing,
both volumes have approximately the same percentage of used space.
# showfdmn usr_domain
Id Date Created LogPgs Version Domain Name
3437d34d.000ca710 Mon Apr 3 10:50:05 2000 512 4 usr_domain
Vol 512-Blks Free % Used Cmode Rblks Wblks Vol Name
1L 1488716 549232 63% on 128 128 /dev/disk/dsk0g
2 262144 262000 0% on 128 128 /dev/disk/dsk4a
--------- ------- ------
1750860 811232 54%
# balance usr_domain
balance: Balancing domain 'usr_domain'
balance: Balanced domain 'usr_domain'
# showfdmn usr_domain
Id Date Created LogPgs Version Domain Name
3437d34d.000ca710 Mon Apr 3 10:50:05 2000 512 4 usr_domain
Vol 512-Blks Free % Used Cmode Rblks Wblks Vol Name
1L 1488716 689152 54% on 128 128 /dev/disk/dsk0g
2 262144 122064 53% on 128 128 /dev/disk/dsk4a
--------- ------- ------
1750860 811216 54%
4.11 Moving Filesets to Different Volumes
iostat
utility either from the SysMan Monitoring
and Tuning - View Input/Output (I/O) Statistics utility, or from the command
line (see
iostat(1)).
If the filesets or domains are located on devices
that appear to be a bottleneck, you can
vdump
command to copy the fileset
from the old device.
Use the
vrestore
command to restore
it to the newly mounted fileset.
/etc/fstab
file.
mkfdmn(8).
The
vdump
and
vrestore
utilities are not affected by the change of DVN.
accounts
with
the fileset
technical
to volume
dsk3c.
The domain
new_accounts
is the temporary domain and is
mounted initially at
/tmp-mnt.
Assume the fileset
accounts#technical
is mounted on
/technical.
Assume that the
/etc/fstab
file has an entry instructing
the system to mount
accounts#technical
on
/technical.
# mkfdmn /dev/disk/dsk3c new_accounts
# mkfset new_accounts technical
# mkdir /tmp_mnt
# mount new_accounts#technical /tmp_mnt
# vdump -dxf - /technical|vrestore -xf - -D /tmp_mnt
# umount /technical
# umount /tmp_mnt
# rmfdmn accounts
# rmdir /tmp_mnt
# mv /etc/fdmns/new_accounts/ /etc/fdmns/accounts/
# mount accounts#technical /technical
4.12 Migrating Files to Different Volumes
migrate
utility to move heavily accessed or large files to a different
volume in the domain.
The
balance
and
defragment
utilities also migrate files but are not under user control.
You
can specify the volume where a file is to be moved or allow the system to
pick the best space in the domain by using the
migrate
command.
You can migrate either an entire file or specific pages to the same
or a different volume.
Figure 4-2
illustrates the migration
process.
migrate
-d
command:
migrate -d destination_vol_index file_name
migrate
command to defragment
selected files.
migrate
utility:
migrate
utility does not evaluate your
migration decisions.
For example, you can move more than one striped file
segment to the same disk, which defeats the purpose of striping the file.
migrate
utility over the
balance
utility when you want to control the movement of individual files.
The
balance
utility moves files only to optimize distribution.
For example, it might move many small files when moving a single larger file
would be a better solution for your system.
migrate
utility over the
defragment
utility when you want to defragment an individual file.
If you
have a large enough contiguous area on disk, you can migrate the file to that
area to defragment it.
showfile -x
command to look at the
extent map and the performance of a file.
A low performance rate (less than
80%) indicates that the file is fragmented on the disk.
The extent map shows
whether the entire file or a portion of the file is fragmented.
4.12.2 Migrate Example
src
and migrates the file.
The file, which resides in a two-volume
domain, shows a change from 11 file extents to one and a performance efficiency
improvement from 18% to 100%.
# showfile -x src
Id Vol PgSz Pages XtntType Segs SegSz I/O Perf File
8.8002 1 16 11 simple ** ** async 18% src
extentMap: 1
pageOff pageCnt vol volBlock blockCnt
0 1 1 187296 16
1 1 1 187328 16
2 1 1 187264 16
3 1 1 187184 16
4 1 1 187216 16
5 1 1 187312 16
6 1 1 187280 16
7 1 1 187248 16
8 1 1 187344 16
9 1 1 187200 16
10 1 1 187232 16
extentCnt: 11
# migrate -d 2 src
# showfile -x src
Id Vol PgSz Pages XtntType Segs SegSz I/O Perf File
8.8002 1 16 11 simple ** ** async 100% src
extentMap: 1
pageOff pageCnt vol volBlock blockCnt
0 11 2 45536 176
extentCnt: 1
src
file now resides on volume 2 of the domain,
consists of one file extent, and has a 100% performance efficiency.
Note that
in the command output, the first data line of the display lists the metadata.
The metadata does not migrate to the new volume.
It remains in the original
location.
The
extentMap
portion of the display lists the
file's migrated pages.
4.13 Striping Files
Note
stripe
utility distributes
stripe -n volume_count
filename
stripe: advfs_set_bf_attributes failed-ENOT_SUPPORTED (-1041)
stripe
utility to modify the number
of disks that an already striped file crosses or to restripe a file that is
already striped.
To change the configuration of a striped file, you must create
a new file, stripe it, then copy the original file data to it.
/etc/fstab
file.
4.13.1 Choosing to Use AdvFS Striping on a File
stripe
utility, run the
iostat
utility either from the SysMan Monitoring and Tuning - View
Input/Output (I/O) Statistics utility, or from the command line to determine
if disk I/O is causing the bottleneck.
See
iostat(1)
for more information.
Cross check the blocks per second and transactions per second with the drive's
sustained transfer rate.
Maximum stripe performance can be achieved if each
stripe disk is on its own disk controller.
4.13.2 AdvFS Stripe Example
file_1,
stripes it, copies data from the original file,
orig_file_1,
into the striped file, then displays the extents of the striped file:
# touch file_1
# ls -l file_1
-rw-r--r-- 1 root system 0 Oct 07 11:06 file_1
# stripe -n 3 file_1
# cp orig_file_1 file_1
# showfile -x file_1
Id Vol PgSz Pages XtntType Segs SegSz I/O Perf File
7.8001 1 16 71 stripe 3 8 async 100% file_1
extentMap: 1
pageOff pageCnt volIndex volBlock blockCnt
0 8 2 42400 384
24 8
48 8
extentCnt: 1
extentMap: 2
pageOff pageCnt volIndex volBlock blockCnt
8 8 3 10896 384
32 8
56 8
extentCnt: 1
extentMap: 3
pageOff pageCnt volIndex volBlock blockCnt
16 8 1 186784 368
40 8
64 7
extentCnt: 1
4.13.3 Removing AdvFS Striping
rmvol
utility moves the segment to another volume that does not
already contain a stripe segment of the same file.
If all remaining volumes
contain stripe segments, the system requests confirmation before the segment
is moved to a volume that already contains a stripe segment of the file.
To
retain the full benefit of striping when this occurs, stripe a new file across
existing volumes and copy the file with the doubled-up segments to the new
file.
4.14 Controlling Domain Panic Information
AdvfsDomainPanicLevel
attribute allows you to
choose whether to have crash dumps created when a domain panic occurs.
Values
of the attribute are:
sysconfig(8)
for information on changing attributes.
See
Section 5.8.6
for information about recovering from a domain
panic.