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Ready NAS 104 iscsi_lun_backing_store using to much disk space


Ready NAS 104 iscsi_lun_backing_store using to much disk space


We have a readynas 104 with 2 4TB Drives configured in JBOD mode meaning each drive is independant of each other and no RAID. One of the drives is used to backup one server and the other drive is used for another server connecting to readynas using isci initiator. When the drive is attached to the Windws server it shows as a 3.26TB volume with 1.54TB of free disk space however, I am getting alerts from readynas that the volume is at 95% capacity. When I looked deep into the issue I found the following file iscsi_lun_backing_store using 3.3TB of disk space. 

It seems that when we are doing backup cleanups by removing old snapshots the data is not being purged from the iscsi_lun_backing_store file.


How do we go about purging data in that iscsi_lun_backing_store file without deleting the file as we will loose all the server backups?



Model: RN104|ReadyNAS 100 Series 4- Bay
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Re: Ready NAS 104 iscsi_lun_backing_store using to much disk space



Welcome to the Community!


What is the declared size of your iscsi_lun_backing_store? HAve you set it up using Thick or Thin provision?


If it is a Thick LUN then once it is set the NAS automatically sees the declared space as used and if you have 3.2TB declared out of 4TB then it is at about 95% of your capacity and the reason you are seeing a different number on Windows is due to the LUN has been formatted already to NTFS which Windows OS is using, The numbers projected on Windows will not be the same with the NAS.


The NAS only see the LUN as 3.26TB even with or without any files in it.


Have you checked if your data can still be accessed? It would be best to get a full backup before doing any expansion or deletion.






Message 2 of 3

Re: Ready NAS 104 iscsi_lun_backing_store using to much disk space


Thank you for responding. I had to blow out the LUN and recreate it. I can't recall now if it was thin or thick but either way it still had a max capacity set to 3.2TB so the file should not grow past 3.2TB. The problem was that the isci_lun_backing_store file grew past the defined capacity and used all 4TB of space on the volume. On Windows it still showed as a 3.26TB drive but at the LUN level it was using more than that. As I was monitoring the backup I kept seeing the disk used space on the LUN grow incrementally until the entire 4TB disk was full while Windows still reported there ws 1.54TB of space available. Very strange. Its almost like when we cleared up snapshots at the OS level to regain space it still held the usage at the LUN level and did not purge but to go over the configured LUN capacity was worst.

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