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Forum Discussion
iSCSI LUN - Unable to use all available disk space
Hello,
We have a ReadyNAS 316 Diskless Model that we purchased and added 6 x 6 TB Western Digital Red Hard Drives (compatible as per HCL). A new RAID 0 volume has been created providing us with 32 TB of available disk space.
When attempting to create a new iSCSI LUN, Thick Provision, no Snapshot Schedule, it is only allowing me to use 29 TB of disk space (or 90% of free space). If I accept this and attempt to create a second LUN there is no free disk space available.
Since there is no redundancy available in my configuration, why are we losing 10% of disk space?
Grateful for any assistance with this.
Thank You
4 Replies
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That's a very risky RAID configuration. If a disk fails all the data is lost.
It's important not to fill your volume too full so we restrict how much space can be used by iSCSI
Welcome to the Community!
Thank You for your quick response.
Regardless of the RAID configuration (X-RAID, RAID 5, RAID 0), you still only allow 90% of the available disk space for new iSCSI LUN's. I am unable to find any documentation that tells us why this is. Disappointed as it may be lead our company to look at other products.
If you fill the volume too full then you will run into performance problems or worse. This true with any filesystem.
We don't allow using more than 90% for iSCSI LUNs due to the unacceptable performance problems this would lead to.
We'd recommend keeping volume usage under 80% and scheduling regular volume maintenance.
There are two related answers.
Netgear don't support creating partition-based iSCSI volumes, which would resolve this problem AND give better performance. They use file-based iSCSI containers.
Netgear also force you to use BTRFS as the file system. This pretty new file system can behave super bad when filled up (for example with a huge iSCSI file). So they limit volume creation, effectively forbidding you from using 10% of the storage you paid for.
So, in short: Netgear's choices have led to this situation. Of course it's unacceptable but what can you do, except choose other products.
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