I have a NAS server with 12 1T drives in a RAID10 linux soft array. The main data area is a 5.4TB XFS partition. On that partition, I've been creating iSCSI disk images, taking advantage of XFS's ability to "thin provision" space. That means allocating more disk than you are immediately going to use (i.e. oversell the disk). I currently have about 15TB allocated, though only about 4.5TB are actually used.
I need to setup a backup for this partition, but I don't want to create a 15+TB array to hold it, which I would need if I copied the disk images over directly.
My questions are: 1) How could I copy that partition without requiring the full allocated space. Would the LVM snapshot handle this? 2) Is there any way to do incremental backups of it (the backup will happen nightly and I don't want a multiple-TB transfer choking my network every night).
Here is my volume/partition configuration if it helps:
vgdisplay dedvol --- Volume group --- VG Name dedvol System ID Format lvm2 Metadata Areas 5 Metadata Sequence No 10 VG Access read/write VG Status resizable MAX LV 0 Cur LV 1 Open LV 1 Max PV 0 Cur PV 5 Act PV 5 VG Size 5.46 TB PE Size 4.00 MB Total PE 1430796 Alloc PE / Size 1414656 / 5.40 TB Free PE / Size 16140 / 63.05 GB VG UUID o1U6Ll-5WH8-Pv7Z-Rtc4-1qYp-oiWA-cPD246 lvdisplay /dev/dedvol/servers --- Logical volume --- LV Name /dev/dedvol/servers VG Name dedvol LV UUID CcNLcI-1OgM-Slb3-JDg4-3Tak-PH7d-SxTzf8 LV Write Access read/write LV Status available # open 1 LV Size 5.40 TB Current LE 1414656 Segments 5 Allocation inherit Read ahead sectors auto - currently set to 256 Block device 253:2