the disk is offline because it is out of capacity ISCSI LUN

I have a Synology DS1513+ with 5 x 2TB HDDs. the whole volume (RAID5) is used as a single ISCSI LUN (with thin provisioning is enabled) and used as a backup drive for the server (Server 2012R2) due to some unexpected data transfers it looks like we have maxed out the capacity and need to delete some files. However Disk management has marked the disk as offline as its out of capacity. The problem I have is when I try to enable it again disk management immediately disables it and marks it as offline so I cannot get to the files and free up some space. Any suggestions? Thanks in advance
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Do not have Synology.

Try going through the iscsi initiator and disconnect/reconnect there or at least make sure the connection is still active.

How was the LUN partitioned as a GPT volume?

Check whether the device, synology is reporting any issues/errors on its end.
Check the vendor site to see whether there is a firmware update that addresses an issue such as yours.

8TB of backups filled up?
Rick HobbsRETIREDCommented:
What version of DSM are you using?
Newer versions include the 2012 UNMAP support dealing with file deletion/reclamation described in the newest release notes:

Re: rickhobs, ......

Depending on the current version, you may have to go through several updates.
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Davis McCarnOwnerCommented:
Because it is already offline, it should be safe to use the web interface to delete some files and free up space.  Have you tried that?
Dead_EyesAuthor Commented:
Hi all sorry for late reply, Its running the latest DSM version and I can't seem to find any way to view the contents of a LUN. File manager seems to only deal in shares ect :(. I am looking at the Synology forums as and when I get 5 but I have not managed to find any useful info so far
Could you try the disconnect/connect method with the iscsi initiator?  It may clear out stale records and free up files and will bring it online.
Dead_EyesAuthor Commented:
Hi Arnold, that's for the suggestion but I have already tried that and rebooting the server and rebooting the NAS
Can you disconnect, and attach the LUN to a different system?
Dead_EyesAuthor Commented:
Still getting the same issue, seems like I need some form of force online command :(
list disk
select disk <number of 8TB>
see if that helps.
Davis McCarnOwnerCommented:
Geeze! The users manual says you can use FTP or FileStation to access it and you should be able to delete files with either:
Dead_EyesAuthor Commented:
Hi Davis, I cannot find a reference in the PDF you linked. What page where you looking at?
Davis McCarnOwnerCommented:
Page 50 and 53
Dead_EyesAuthor Commented:
Pages 50 and 53 cover accessing files on a share from FTP but nothing about accessing an iSCSI LUN or connecting to one
Jim_NimSenior EngineerCommented:
If you're using thin-provisioning on the storage array and ran out of disk space to accommodate growth of new space allocation on the virtual disk, the array likely set the volume into a read-only state (as there is no space to accommodate writes). I don't think the volume is in an "offline" state on the storage side if you still have a connection to the disk device and it's showing up in disk management - the disk is likely just in a read-only state.

Here's the problem: You can't online the disk in disk management (which auto-mounts the file system) if it's in a read-only state. Windows requires the ability to write to the volume in order to mount it normally (there is a small amount of metadata that is immediately written when mounting).

You may be able to mount the volume in a read-only state within windows (e.g. disable auto-mount with mountvol.exe /N then set the read-only flag with diskpart), but that still doesn't allow you the write access you need to delete files (or "rethin" with SCSI UNMAP, which latest software/firmware versions appear to support).

Since the storage array isn't going to have any "visibility" into the file system layer, your only option here is likely going to be increasing the block-level storage that the enclosure has available to allocate for this volume, even if that means moving data off of another volume so that it can be deleted. If you have absolutely no remaining space on the array outside this volume (i.e. 100% usable capacity allocated to this single volume), I'd suggest looking into one of these options:
Add disks to any available drive slots and expand the RAID (if the system supports this action)
Look into what this enclosure supports in terms of live-upgrading hard drives to larger capacity models.
Consider adding an expansion enclosure - this system supports expanding out to 60TB max with expansion enclosures
Look into whether or not this enclosure supports RAID type conversion. If it does, you may be able to convert from whatever RAID level you've chosen to one that provides more storage capacity (e.g. RAID6 -> RAID5, RAID5 -> RAID0). This will affect the system's redundancy though, so this may only work as a temporary solution until you can free up space at a file system level

If/when you're able to get the volume back online by some means, I would strongly recommend that you start off by "rethinning" the volume using the Windows "Defragment & Optimize Drives" tool. This runs once per week by default already though, so it may not make a big difference. Next, start searching for files to delete to free up space. If they're small enough, Windows won't send SCSI UNMAP commands on the fly to reflect all the changes on the block level & storage array side, so you may need to re-run another optimization.

Note: I don't have any experience with this particular enclosure/system - my comments draw from a few years' experience with Enterprise-class storage systems that also deal with thin-provisioning support.

Good luck!

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This is only tangentially related, but RAID 5 is not safe with hard drives larger than 1 TB. If a drive were to fail you have a non-trivial risk of having a second drive fail or encountering an unrecoverable read error (URE).

I don't consider Synology anywhere close to enterprise class.
Dead_EyesAuthor Commented:
Hi Kevin, thanks for comment but I don't see the relevancy.
1.) "not safe" is hardly a technically precise term. May I suggest not fit for the purpose of X would have been a more relevant way to start that comment. (by the way the purpose of the NAS is as one of two backups)
2.) The only data I can find to support that claim is woefully outdated and based on error rates staying the same as they where 10, 15 years ago while volume size increases
3.) I have 100 plus systems in our company / client base running RAID 5 setups and have never had data corruption or URE's reported by engineers or clients in 6+ years so I cannot relate that to a real life POV
4.) Considering the importance of the data, backup routine and track record of data loss  (0% in 6+ years). I would consider RAID 5 perfectly adequate for our needs and higher RAID levels not justified for most of our clients needs. (those that do have need of greater redundancy use RAID 6 and 6 +hotspare)
5.) While RAID 5, 6, 10, 50, 60 ect have their intended uses different products by different company also have their place. While you might not consider Synologys products to be relevant to your company's needs many people do and I don't think your use of the term "enterprise class" is in any way a POV many people would share.
Dead_EyesAuthor Commented:
@ Jim_Nim thanks for a great explanation Jim I am just exploring a few options today but I suspect your 100% right and will award you the points in the next 12 hours or so I just need to try a couple of last ditch things but am taking it a lesson learned: Never setup a LUN with 100% of your available capacity
Any possibility to access the LUN from a non windows system to see whether it will remain active

Look at testsisk to see whether it could access the partition while the disk reflected os offline.

Not sure whether diskpart can be used to check the status of the LUN.
Davis McCarnOwnerCommented:
Sine the iSCSI LUN is offline, there is no point in attempting to connect to it using iSCSI.  FTP directly into the Synology and see if it will let you delete files!
I think the following , over allocation, might explain your situation.

Linux can mount partitions read-only and this might let you get the data off.

Have you reached out to Synology to see what their options are?
I believe it was suggested to attach an additional external drive/resource if possible to allow it to be used for the excess data so the LUN can "expand" and return to a mode where it once again will be seen as online on the windows system.

Jim_NimSenior EngineerCommented:
@Dead_Eyes - In regards to the use of RAID5, "unsafe" really isn't too far off from the truth... though more technically accurate terminology would be that its use for storing business-critical data is not recommended & discouraged according to industry standard best practices. The fact of the matter is, RAID5 has never been "safe" - it's RAID. No RAID should be solely entrusted with the only existing copy of any critical data, it should always be backed up elsewhere.

It sounds like you've already weighed the risks and benefits though, and you have a backup strategy in place, so you've not by any means made a wrong decision. Typically the people who get hit hard by RAID5 problems are those who are both unaware of the potential risks and unprepared for them.
Dead_EyesAuthor Commented:
Good explanation and although I decided to trash the LUN as the data was non-critical and replaced weekly I hope someone can make use of this to fix or plan and avoid this situation.
My comment about Synology not being enterprise class is that I wouldn't assume that techniques available on tier 1 enterprise arrays are available to Synology.

Current industry practice is to not use RAID 5 for primary storage when drives are 1 TB or larger. URE rates haven't really changed over the years, but drives have gotten larger, making the probability of a URE taking down the entire array non-trivial. If you can afford to lose the entire array, such as in this case, then it is less of a concern.
i have found the exact issue i have elsewhere on this site... think they blew it away though..will look now..

i have attached a doc with the requested screenshos...  i will need to find a away to get the disk online even tough it does not have enough free space... once i get it online i will be able to free space immediately..
sorry..!  posed in wrong question
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Windows Server 2012

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