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Growing an NTFS iSCSI volume that's hosted on ZFS

One of the many problems I face in my ridiculous mountain of ‘stuff to care about’ at work is a rather write-heavy MSSQL database. By write-heavy, it’s only something like 60-70 thousand inserts per day, and so far there’s over 6 million rows on on of the tables. When you’re taking full daily backups and transaction log backups every 15 minutes, disk space starts to run thin quickly.

I recently migrated that particular MSSQL server onto a 2-node failover cluster (takes a while to get right when both servers are VMs on VMware’s vSphere 4.1). This works rather well. The shared storage is provided over iSCSI from a Solaris 11 Express box.

When I initially set up the cluster and was generating the LUNs, I just assumed ‘100Gb’ or so would be enough. It turns out, it’s not enough. Thinking this would be a major thing to resolve, I set aside a few hours to try and figure it out. To my surprise, it was surprisingly easy and took about 10 minutes. Here’s how.

Step 1: First you have to make the ZFS volume bigger. Falling into exactly the same trap as before, I just said “Oh, 300Gb is surely going to be enough”. I did this:

$ zfs set volsize=300G tank/comstar/sqldata

Step 2: Now, you need to tell SCSI block disk thingie that the LUN’s changed. Otherwise, it’s got no clue what’s going on.

$ sbdadm modify-lu -s 300g

Step 3: Head over to Windows, open the disk storage manager where (hopefully) it should have recognised that you’ve got a massively bigger disk with a tiny partition, hit right-click and “Extend”.

That’s it. It seems to work. Best of all, no iSCSI disconnects, no MSSQL burps, the data collector didn’t notice and just ploughed on.

I love ZFS. Shame Oracle had to ruin everything.