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Q: Does
alt_disk_copy convert JFS filesystems to JFS2?
A: Yes! Starting at 6100-04, a new
flag was introduced that would convert JFS filesystems to JFS2. We now have the
-T which does the conversion.
http://www-01.ibm.com/support/docview.wss?uid=isg3T1011055
Here’s an example of converting rootvg file systems from JFS to JFS2 using alt_disk_copy.
My lab system was migrated from AIX 5.3 to 7.1 via nimadm. Unfortunately, nimadm does not convert JFS file systems to JFS2 during the migration. So, in this case, even though I’ve migrated to AIX 7.1 (which is a good thing) I’m still left with legacy JFS file systems in rootvg.
And because the AIX 5.3 version of the alt_disk_copy command does not have the –T option, I can’t convert my JFS file systems to JFS2 before I migrate to AIX 7.1. So my best option is to migrate to AIX 7.1 then convert rootvg to JFS2 file systems. A few hops in the process but it’s good enough.
aixlpar1 : / # lsvg -l rootvg
rootvg:
LV NAME TYPE LPs PPs PVs LV STATE MOUNT POINT
hd5 boot 1 1 1 closed/syncd N/A
hd6 paging 32 32 1 open/syncd N/A
hd8 jfslog 1 1 1 open/syncd N/A
hd4 jfs 4 4 1 open/syncd /
hd2 jfs 29 29 1 open/syncd /usr
hd9var jfs 20 20 1 open/syncd /var
hd3 jfs 164 164 1 open/syncd /tmp
hd1 jfs 4 4 1 open/syncd /home
hd10opt jfs 4 4 1 open/syncd /opt
local jfs 4 4 1 open/syncd /usr/local
loglv jfs 4 4 1 open/syncd /var/log
hd7 sysdump 9 9 1 open/syncd N/A
hd71 sysdump 9 9 1 open/syncd N/A
hd11admin jfs 2 2 1 open/syncd /admin
aixlpar1 : / # oslevel -s
7100-01-01-1141
I clone rootvg to a spare disk using alt_disk_copy and the –T flag (which will convert the file systems to JFS2). The process converts the file systems to JFS2, as shown in the section below (highlighted in green).
aixlpar1 : / # alt_disk_copy -d hdisk1 -T
Source boot disk is: hdisk2
jfs2j2: Current data file /image.data moved to /image.data.acct.save.3735802.
jfs2j2: Creating new data file (/image.data).
jfs2j2: Converting filesystems in data file (/image.data) from jfs to jfs2.
jfs2j2: Converted data file (/image.data) moved to /tmp/image.data.conv.3407932.
jfs2j2: Cleaning up.
jfs2j2: Moving previous data file /image.data.acct.save.3735802 to IDFILE.
jfs2j2: Successfully completed converting image.data to jfs2.
Checking disk sizes.
Creating cloned rootvg volume group and associated logical volumes.
Creating logical volume alt_hd5
Creating logical volume alt_hd6
Creating logical volume alt_hd8
Creating logical volume alt_hd4
Creating logical volume alt_hd2
Creating logical volume alt_hd9var
Creating logical volume alt_hd3
Creating logical volume alt_hd1
Creating logical volume alt_hd10opt
Creating logical volume alt_local
Creating logical volume alt_loglv
Creating logical volume alt_hd7
Creating logical volume alt_hd71
Creating logical volume alt_hd11admin
Creating /alt_inst/ file system.
/alt_inst filesystem not converted.
Small inode extents are already enabled.
Creating /alt_inst/admin file system.
/alt_inst/admin filesystem not converted.
Small inode extents are already enabled.
Creating /alt_inst/home file system.
/alt_inst/home filesystem not converted.
Small inode extents are already enabled.
Creating /alt_inst/opt file system.
/alt_inst/opt filesystem not converted.
Small inode extents are already enabled.
Creating /alt_inst/tmp file system.
/alt_inst/tmp filesystem not converted.
Small inode extents are already enabled.
Creating /alt_inst/usr file system.
/alt_inst/usr filesystem not converted.
Small inode extents are already enabled.
Creating /alt_inst/usr/local file system.
/alt_inst/usr/local filesystem not converted.
Small inode extents are already enabled.
Creating /alt_inst/var file system.
/alt_inst/var filesystem not converted.
Small inode extents are already enabled.
Creating /alt_inst/var/log file system.
/alt_inst/var/log filesystem not converted.
Small inode extents are already enabled.
Generating a list of files
for backup and restore into the alternate file system...
Backing-up the rootvg files and restoring them to the
alternate file system...
Running user specified customization script /tmp/cust.script.conv.3407932...
Modifying ODM on cloned disk.
Building boot image on cloned disk.
forced unmount of /alt_inst/var/log
forced unmount of /alt_inst/var
forced unmount of /alt_inst/var
forced unmount of /alt_inst/usr/local/chksys
forced unmount of /alt_inst/usr/local
forced unmount of /alt_inst/usr
forced unmount of /alt_inst/tmp
forced unmount of /alt_inst/opt
forced unmount of /alt_inst/home
forced unmount of /alt_inst/admin
forced unmount of /alt_inst
Changing logical volume names in volume group descriptor area.
Fixing LV control blocks...
Fixing file system superblocks...
Bootlist is set to the boot disk: hdisk1 blv=hd5
Before I reboot the system on the alternate rootvg I verify that the cloned volume group now contains JFS2 file systems only. I “wake up” the altinst_rootvg and run the lsvg command to confirm the file system is correct. I then put the altinst_rootvg to “sleep”, reboot the system and verify all rootvg file systems are mounted as jfs2.
aixlpar1 : / # alt_rootvg_op -W -d hdisk1
Waking up altinst_rootvg volume group ...
aixlpar1 : / # lsvg -l altinst_rootvg
altinst_rootvg:
LV NAME TYPE LPs PPs PVs LV STATE MOUNT POINT
alt_hd5 boot 1 1 1 closed/syncd N/A
alt_hd6 paging 32 32 1 closed/syncd N/A
alt_hd8 jfs2log 1 1 1 open/syncd N/A
alt_hd4 jfs2 4 4 1 open/syncd /alt_inst
alt_hd2 jfs2 29 29 1 open/syncd /alt_inst/usr
alt_hd9var jfs2 20 20 1 open/syncd /alt_inst/var
alt_hd3 jfs2 164 164 1 open/syncd /alt_inst/tmp
alt_hd1 jfs2 4 4 1 open/syncd /alt_inst/home
alt_hd10opt jfs2 4 4 1 open/syncd /alt_inst/opt
alt_local jfs2 4 4 1 open/syncd /alt_inst/usr/local
alt_loglv jfs2 4 4 1 open/syncd /alt_inst/var/log
alt_hd7 sysdump 9 9 1 closed/syncd N/A
alt_hd71 sysdump 9 9 1 closed/syncd N/A
alt_hd11admin jfs2 2 2 1 open/syncd /alt_inst/admin
aixlpar1 : / # alt_rootvg_op -S altinst_rootvg
Putting volume group altinst_rootvg to sleep ...
forced unmount of /alt_inst/var/log
forced unmount of /alt_inst/var
forced unmount of /alt_inst/usr/local
forced unmount of /alt_inst/usr
forced unmount of /alt_inst/tmp
forced unmount of /alt_inst/opt
forced unmount of /alt_inst/home
forced unmount of /alt_inst/admin
forced unmount of /alt_inst
Fixing LV control blocks...
Fixing file system superblocks...
aixlpar1 : / #
; Reboot on the alternate rootvg hdisk
aixlpar1 : / # uptime
10:18AM up 1 min, 1 user, load average: 0.32, 0.09, 0.03
aixlpar1 : / # lspv
hdisk1 00c342c637f21a59 rootvg active
hdisk2 00c342c6161c6b47 old_rootvg
aixlpar1 : / # df
Filesystem 512-blocks Free %Used Iused %Iused Mounted on
/dev/hd4 524288 411568 22% 3040 7% /
/dev/hd2 3801088 537176 86% 34089 35% /usr
/dev/hd9var 2621440 2413520 8% 3554 2% /var
/dev/hd3 21495808 21476312 1% 110 1% /tmp
/dev/hd1 524288 522456 1% 90 1% /home
/proc - - - - - /proc
/dev/hd10opt 524288 266560 50% 5133 15% /opt
/dev/local 524288 495320 6% 249 1% /usr/local
/dev/loglv 524288 522040 1% 49 1% /var/log
/dev/hd11admin 262144 261384 1% 7 1% /admin
aixlpar1 : / # lsvg -l rootvg
rootvg:
LV NAME TYPE LPs PPs PVs LV STATE MOUNT POINT
hd5 boot 1 1 1 closed/syncd N/A
hd6 paging 32 32 1 open/syncd N/A
hd8 jfs2log 1 1 1 open/syncd N/A
hd4 jfs2 4 4 1 open/syncd /
hd2 jfs2 29 29 1 open/syncd /usr
hd9var jfs2 20 20 1 open/syncd /var
hd3 jfs2 164 164 1 open/syncd /tmp
hd1 jfs2 4 4 1 open/syncd /home
hd10opt jfs2 4 4 1 open/syncd /opt
local jfs2 4 4 1 open/syncd /usr/local
loglv jfs2 4 4 1 open/syncd /var/log
hd7 sysdump 9 9 1 open/syncd N/A
hd71 sysdump 9 9 1 open/syncd N/A
hd11admin jfs2 2 2 1 open/syncd /admin
===
The message “filesystem not converted” (below) is not related to the JFS to JFS2 conversion. This messge refers to whether or not the file system needs to be changed to use Variable Inode Extents (VIX). This is the default setting for JFS2 file systems.
Creating /alt_inst/ file system.
/alt_inst filesystem not converted.
Small inode extents are already enabled.
aixlpar1 : / # lsfs -q /
Name Nodename Mount Pt VFS Size Options Auto Accounting
/dev/hd4 -- / jfs2 524288 -- yes no
(lv size: 524288, fs size: 524288, block size: 4096, sparse files: yes, inline log: no, inline log size: 0, EAformat: v1, Quota: no, DMAPI: no, VIX: yes, EFS: no, ISNAPSHOT: no, MAXEXT: 0, MountGuard: no)
aixlpar1 : / #
Please refer to the following link for more information on VIX in AIX.
Use of Variable Inode Extents (VIX) in AIX
http://www-01.ibm.com/support/docview.wss?uid=isg3T1010368
===
Why would I want to convert rootvg to JFS2 anyway? Well for starters, it’s generally considered best practice to use JFS2 as it offers several performance & scalability enhancements over JFS. For example, you cannot create files greater than 2GB on JFS, unless the file system was created as “large (big) file” enabled; jfs file systems in rootvg were never created as large file enabled.
Another reason…..eventually JFS will be retired.
Here’s an example of a potential problem with JFS in rootvg. You try to create a file of a size greater than 2GB in /tmp (type jfs). Even though the ulimit settings are not restricting the creation of a file of this size, the JFS file system will not allow it. The file creation process fails. The bf attribute for the /tmp file system is set to false. This indicates the file system is not “large file” enabled.
aixlpar1 : /tmp # df -g .
Filesystem GB blocks Free %Used Iused %Iused Mounted on
/dev/hd3 10.25 6.94 33% 117 1% /tmp
aixlpar1 : /tmp # cat 1gbfile 1gbfile 1gbfile > 3gbfile
cat: 0652-054 Cannot write to output.
Error 0
aixlpar1 : /tmp # ulimit -a
time(seconds) unlimited
file(blocks) unlimited
data(kbytes) unlimited
stack(kbytes) unlimited
memory(kbytes) unlimited
coredump(blocks) 2097151
nofiles(descriptors) unlimited
threads(per process) unlimited
processes(per user) unlimited
aixlpar1 : /tmp # lsfs -q /tmp
Name Nodename Mount Pt VFS Size Options Auto Accounting
/dev/hd3 -- /tmp jfs 21495808 -- yes no
(lv size: 21495808, fs size: 21495808, frag size: 4096, nbpi: 4096, compress: no, bf: false, ag: 8)
OK, so creating files greater than 2GB in rootvg is probably not a big problem for most AIX shops. But why risk it! My advice is to always use JFS2 (even in rootvg).
Keep this in mind when migrating from AIX 5.3 to 6.1 or 7.1 via nimadm.
The following link provides an overview and comparison of both JFS and JFS2 file systems.
