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1096
ScaleIO using twice as much space as expected
I have a ScaleIO 2.0 deployment in my lab. There are 6 SDS servers with 900GB each.
I created a single 3TB volume, and presented it to a single linux SDC. Nothing else is currently using ScaleIO in my environment. The volume is part of a volume group. This particular logical volume uses XFS. It is the only logical volume in the volume group.
According to the linux server, I am using 1.6TB of the 3TB volume.
In the ScaleIO gui, It shows the following
5.3TB Total
1.8TB Spare
3.4TB Used?????
Protection level and other settings are default from the install. Can anyone help explain where the additional space has gone? Thank you.
andyinv
37 Posts
0
July 28th, 2017 01:00
The GUI is showing the raw space available to ScaleIO as in "how much disk space you have given it", in your case 6*900 = ~5.4TB. As your data is essentially duplicated, if you create and use 1.6tb of a thin-provisioned 3TB volume, then the raw space that will take from your pool is approx twice that, so 2x1.6tb = roughly 3.4tb.
Look into the scli --query_volume command for more details on how much space is used, but if you're wondering why it's not just using 1.6TB then see above and know that you don't get a single-instance copy of your data. That never happens in ScaleIO, it's always duplicated. Mirrored, whether you like it or not
pawelw1
306 Posts
1
July 28th, 2017 02:00
Hi,
I am assuming you are using thin provisioning, is that correct?
Please remember that in ScaleIO every chunk of data is mirrored - so when you create a 100GB volume "Used space" is actually twice as much, due to mirroring:
scli --add_volume --volume_name test1 --size_gb 104 --storage_pool_name sp1 --protection_domain_name pd1
scli --query_all:
(...)
208.0 GB (212992 MB) in-use capacity
0 Bytes thin capacity
208.0 GB (212992 MB) protected capacity
Hope this helps!
Cheers,
Pawel
clintyjd
2 Posts
0
July 28th, 2017 16:00
Thank you very much. I was thinking of it as a RAID5 sort of deal where you lose a drive's worth of capacity to parity in the array. In actuality, though, for ScaleIO, it's (Total - spare)/2. That's a pretty hefty penalty as far as capacity is concerned, but then again, I do like to keep my data safe! Thanks again!