| Question |
| What is LVM? |
| Answer |
| LVM stands for Logical Volume Manager . LVM is a tool for logical volume management which includes allocating disks, mirroring and resizing logical volumes. |
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| Question |
| What is logical partition? |
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| Answer |
| Logical volumes consist of one or more logical partitions (LPs). Each logical partition has at least one corresponding physical partition. A logical partition and a physical partition always have the same size. You can have up to three copies of the data located on different physical partitions. Usually, physical partitions storing identical data are located on different physical disks for redundancy purposes. |
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| Question |
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| What is dameon? |
| Answer |
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| In UNIX terminology we generally refer services as daemons. Its equivalent to services in windows, here in UNIX we have a directories for the daemons to start and stop. |
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| Question |
| How can we change the pp size? |
| Answer |
| Normally we cant change the PP size once the PV is the part of VG . But PP size can be changed later using a T-factor. |
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| Question |
| How to do you scan the new LUN or disk for LVM physical volume? |
| Answer |
| using the cfgmgr command |
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| Question |
| How do I create a volume group? |
| Answer |
| with the help of mkvg command, mkvg -y vgname |
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| Question |
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| How do I create a logical volume? |
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| Answer |
| We can create either by smitty mklv or through command line mklv -y |
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| Question |
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| How do I know if my volume group is normal, big, or scalable? |
| Answer |
| lsvg vgname – see max PVs, if its 32, its normal vg |
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| Question |
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| How can I change the characteristics of a volume group? |
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| Answer |
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| Through chvg command we canchange the characteristics of a volume group. |
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| Question |
| How can I change the characteristics of a volume group? |
| Answer |
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| Using chvg command, or using smitty chvg |
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| Question |
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| How can we change the PP size? |
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| Answer |
| Normally we cant change the PP size once the PV is the part of VG . But PP size can be changed later using a T-factor. |
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| Question |
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| What is LVM? |
| Answer |
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| LVM stands for Logical Volume Manager . LVM is a tool for logical volume management which includes allocating disks, mirroring and resizing logical volumes. |
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| Question |
| How do I display all logical volumes that are part of a volume group? |
| Answer |
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| lsvg -l |
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| Question |
| What are LVM1 and LVM2?how can we create it? |
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| Answer |
| LVM 1 and LVM 2 are terminologies used red hat linux LVM, in AIX we have only LVM |
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| Question |
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| How do I mirror a logical volume? |
| Answer |
| through mklvcopy command |
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| Question |
| One of my JFS filesystem is full, how can we increase that filesystem & it is throwing error NBPI is fixed. |
| Answer |
| NBPI is fixed in case of JFS filesystem, we no longer use jfs now, we are using jfs2 nowadays and in that NBPI is dynamic |
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| Question |
| Is there any possibilities to convert a normal vg to scalable and bigvgs , also is it possible to change the size of pp once a vg is created |
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| Yes , we can convert …. No the PP size cannot be changed |
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| Question |
| How do I know if my volume group is normal, big, or scalable? |
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| Answer |
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| Through lsvg command on the volume group and look at the value for MAX PVs. The value is 32 for normal, 128 for big and 1,024 for scalable volume group. |
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| Question |
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| How to replace the failed hard disk in LVM ? |
| Answer |
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| If it is mirrored , we break the mirror , check for lv’s on the failed disk, if they are, we will move them to the other disk, the reducevg and after that we delete the disk using rmdev command |
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| Question |
| How to copy a LV from one VG to another? |
| Answer |
| Through cplv command |
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| Question |
| How will you unmirror a VG if a PV gets failed? |
| Answer |
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| Normally a PV does not get failed completely , only it’s got stale partitions. in general scenario , the system will allow us to do unmirror the volume group. if its not allowing us to do unmirror the volume group, we have to remove the lv copies with the help of rmlvcopy copy manually |
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| Question |
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| How will rename a VG? |
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| Answer |
| using exportvg command and then importvg command with new vg name |
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| Question |
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| Can we shrink a LVM mountpoint ? |
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| Yes we can |
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| Question |
| What is VGDA? What is its importance in LVM. |
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| VGDA is Volume Group Descriptor Area which resides in the first block of the disk and helds the information related to VG the disk belongs to . It has a major role in LVM and a vg cannot be varied on without VGDA |
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| Question |
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| Please explain quorum what it is and its significance. |
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| A quorum is a vote of the number of Volume Group Descriptor Areas and Volume Group Status Areas (VGDA/VGSA) that are active. A quorum ensures data integrity of the VGDA/VGSA areas in the event of a disk failure. Each physical disk in a volume group has at least one VGDA/VGSA. |
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| Question |
| JFS2 snapshot , how to take and difference from mksysb, savevg other conventional backups. |
| Answer |
| The JFS2 snapshot command will create an image of a filesystem at a point in time, allowing the user to back up data from the snapshot rather than from the original filesystem. With snapshot, the file system is frozen, ensuring you get a full copy, and avoid ‘open file’, ‘running process’ or ‘file not found’ issues. (There is no need to shut down an application, but it is better to do the snapshot in a quiet time. You can have up to 15 external snapshots of a JFS2 file system and using the rollback utility, external snapshots can be rolled back to the point when a snapshot was taken. snap -o command is used to take jfs2 snapshot. |
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| Question |
| If I do importvg after a exportvg shall i required to varyon maually or it happends automatically with all mount points visible |
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| Answer |
| Depend on what kind of VG you have created, enhanced concurrent or normal vg |
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| Question |
| What are the best pratices in normal world? to use normal, scalable or bigvgs? |
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| Answer |
| There is no such best practice .Rather the use of any type of VG is all upto disk availability as well your business requirement |
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| Question |
| We assign the paging space from a volume group as a paging LV. Is it good to have a mirrored copy of the paging LVs or we can cut different LVs from different disks part of the same VG? |
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| Answer |
| Its always recommended to have paging lv’s from different PV’s |
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| Question |
| How to convert the linear volume to mirror volume? |
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| Through mklvcopy u can convert linear volume to mirror volume |
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| Question |
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| Is there any default value for Max number of LPs per LV? If there is, how can we increase the same if we want to allocate more space to the filesystem. |
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| LP’s are mapped to PP’s and we can have a maximum of 3 PP’s mapped to one LP. There is no limit of max PP’s per LV. |
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| Question |
| What is the concept of Concurrent IO n AIX LVM? Can we incorporate it in any existing environment in case beneficial? |
| Answer |
| A quorum is a vote of the number of Volume Group Descriptor Areas and Volume Group Status Areas (VGDA/VGSA) that are active. A quorum ensures data integrity of the VGDA/VGSA areas in the event of a disk failure. Each physical disk in a volume group has at least one VGDA/VGSA. |
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| Question |
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| What is quoram? |
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| A quorum is a vote of the number of Volume Group Descriptor Areas and Volume Group Status Areas (VGDA/VGSA) that are active. A quorum ensures data integrity of the VGDA/VGSA areas in the event of a disk failure. Each physical disk in a volume group has at least one VGDA/VGSA. |
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| Question |
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| What is the concept of Concurrent IO in AIX LVM? Can we incorporate it in any existing environment in case beneficial? |
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| CIO invokes direct I/O, so it has all the other performance considerations associated with direct I/O. With standard direct I/O, inodes are locked to prevent a condition where multiple threads might try to change the consults of a file simultaneously. Concurrent I/O bypasses the inode lock, which allows multiple threads to read and write data concurrently to the same file. Under CIO, multiple threads may simulteanously perform reads and writes on a shared file. Applications that do not enforce serialization should not use CIO (data corruption or perf. issues can occur.)Oracle implements its own I/O serialization mechanisms to ensure data integrity, so JFS2 offers Concurrent I/O option. |
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| Question |
| Is it clearing the PVID similar to formatting the disk. |
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| No, its different. |
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| Question |
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| What is t factor? |
| Answer |
| T factor is used to change the vg type |
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| Question |
| What is LVCB? |
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| Answer |
| A logical volume control block (LVCB) contains important information about the logical volume, such as the number of the logical partitions or disk allocation policy. Its architecture and location on the disk depends on the type of the volume group it belongs to. |
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| Question |
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| How do I fix Volume Group which is Locked? |
| Answer |
| volume group is locked at the time of mirroring of its LP’s. we can use the command lsvg -L vgname |
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| Question |
| Then what is the difference between clearing the PVID and formatting the disk.How we can format the disk in AIX ? |
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| PVId is just a physical disk identifier or u can say an address of the disk. the data resides on the disk. PVID can be reassigned using the command chdev -l hdiskN -a pv=yes. to format the disk we can go in diag menu and format the disk |
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| Question |
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| How is the PP Size of the rootvg defined? Can we change it during the installation or afterwards? |
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| Answer |
| By default it is 128 for rootvg I guess, its not recommended to change the PP size in the rootvg, whereas you can define the desired PP size while creating the new volume group. PP size play significant role in creating file systems and disk usage. |
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| Question |
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| What is the difference between jfs and jfs2? |
| Answer |
| jfs – maximum file system size – 1 TB, maximum file size – 64 GB , Inode size – 128 bytes , Default ownership at creation – sys.sys , compression – yes jfs2 – maximum file system size – 4 PB, maximum file size -4 PB , Inode size – 512 bytes , Default ownership at creation – root.system , compression – no |
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| Question |
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| What RAID levels are supported? |
| Answer |
| RAID 1 |
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| Question |
| Any possibility is there to reduce the volume in LVM. |
| Answer |
| Yes we can |
