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Growing live Solaris filesystems with metadevices

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Solaris Volume Manager has also been variously known as Disksuite or ODS (but not the Solaris Volume Manager which was the rebadged and bundled Veritas Volume Manager!) and comes with lots of neat features. One of the best is simple method for expanding metadevices and filesystems – on a live system!

For my example today, I’m going to use a Sun T2000 which has 4 zones, all of which are running from a metadevice composed of several 10gb LUNs from a SAN. The object of this exercise is to add another 10gb to the zone filesystem, so the developers can fire up another zone.

The fact that we’re using a metaset from a SAN doesn’t matter – the key thing here is that, by encapsulating a disk (or LUN, or partition) and using a metadevice, we can quickly and easily expand live filesystems.

First of all, let’s have a look at the metaset on the host, which has been imaginatively called ‘zones’:

bash-3.00# metaset -s zones
Set name = zones, Set number = 2
Host                Owner
  bumpkin         Yes (auto)
Drive                                            Dbase
/dev/dsk/c6t60060E80141189000001118900001918d0   Yes  
/dev/dsk/c6t60060E80141189000001118900001919d0   Yes  
/dev/dsk/c6t60060E80141189000001118900002133d0   Yes  

We can use the metastat command to print a summary of the metadevices within the metaset:

bash-3.00# metastat -s zones -c
zones/d100       s   29GB /dev/dsk/c6t60060E80141189000001118900001918d0s0 /dev/dsk/c6t60060E80141189000001118900001919d0s0 /dev/dsk/c6t60060E80141189000001118900002133d0s0

In this case, we’ve got just one metadevice, named d100, which is composed of three 10gb LUNs from the SAN.

So, our first task is to add the newly available LUN to the metaset:

bash-3.00# metaset -s zones -a c6t60060E80141189000001118900001731d0

We can check that it’s really been added with the metaset command again:

bash-3.00# metaset -s zones
Set name = zones, Set number = 2
Host                Owner
  bumpkin         Yes (auto)
Drive                                            Dbase
/dev/dsk/c6t60060E80141189000001118900001918d0   Yes  
/dev/dsk/c6t60060E80141189000001118900001919d0   Yes  
/dev/dsk/c6t60060E80141189000001118900002133d0   Yes  
/dev/dsk/c6t60060E80141189000001118900001731d0   Yes  

Rock on! We’ve now got our 4 10gb LUNs added to the metaset. Now we need to attach the new LUN to our existing 30gb metadevice, d100:

bash-3.00# metattach zones/d100 /dev/dsk/c6t60060E80141189000001118900001731d0s0
zones/d100: component is attached

Note that we don’t need to bring down the three running zones – we can do all of this live, with the system at the multi-user-server milestone.

If we query the metadevice now we can see that it’s grown, from a stated 29GB to 39GB, and that our new LUN is part of the metadevice:

bash-3.00# metastat -s zones -c
zones/d100       s   39GB /dev/dsk/c6t60060E80141189000001118900001918d0s0 /dev/dsk/c6t60060E80141189000001118900001919d0s0 /dev/dsk/c6t60060E80141189000001118900002133d0s0 /dev/dsk/c6t60060E80141189000001118900001731d0s0

Now all we need to do is grow the filesystem, using all of that extra 10gb:

bash-3.00# growfs -M /export/zones /dev/md/zones/rdsk/d100 
/dev/md/zones/rdsk/d100:        83742720 sectors in 13630 cylinders of 48 tracks, 128 sectors
        40890.0MB in 852 cyl groups (16 c/g, 48.00MB/g, 5824 i/g)
super-block backups (for fsck -F ufs -o b=#) at:
 32, 98464, 196896, 295328, 393760, 492192, 590624, 689056, 787488, 885920,
Initializing cylinder groups:
................
super-block backups for last 10 cylinder groups at:
 82773280, 82871712, 82970144, 83068576, 83167008, 83265440, 83363872,
 83462304, 83560736, 83659168

Here’s the output of df before we hacked about:

bash-3.00# df -k /export/zones
Filesystem            kbytes    used   avail capacity  Mounted on
/dev/md/zones/dsk/d100
                     30928078 14451085 16270806    48%    /export/zones

And there’s the output after we’ve expanded the filesystem:

bash-3.00# df -k /export/zones
Filesystem            kbytes    used   avail capacity  Mounted on
/dev/md/zones/dsk/d100
                     41237442 14462125 26569130    36%    /export/zones

So, a quick and simple way to grow a filesystem under Solaris, using metadevices and with no downtime.

Also, a brief note to Sun product managers: choose a name for your products, and stick with that name for more than a year. Thanks!

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One comment to “Growing live Solaris filesystems with metadevices”

  1. Hi Tom,
    Great notes!
    One question though – your example above shows an increase using all of the extra 10Gb. However, what if you only wanted 5Gb?

    E.g. growfs -M /export/zones /dev/md/zones/rdsk/d100 -size 5Gb

    Is there an SVM/metaset command to achieve this? I have this situation at the moment.

    Thanks,
    David

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