Bug 1547674 - slabsize should be increased when physical space of the device exceeds 16TB
Summary: slabsize should be increased when physical space of the device exceeds 16TB
Keywords:
Status: CLOSED CURRENTRELEASE
Alias: None
Product: Red Hat Gluster Storage
Classification: Red Hat Storage
Component: rhhi
Version: rhhiv-1.5
Hardware: x86_64
OS: Linux
high
high
Target Milestone: ---
: ---
Assignee: Gobinda Das
QA Contact: SATHEESARAN
URL:
Whiteboard:
Depends On: 1547675
Blocks:
TreeView+ depends on / blocked
 
Reported: 2018-02-21 16:50 UTC by SATHEESARAN
Modified: 2019-09-13 15:05 UTC (History)
4 users (show)

Fixed In Version:
Doc Type: Known Issue
Doc Text:
Virtual Data Optimizer (VDO) volumes are comprised of up to 8096 slabs. The default slab size is 2GB, which limits VDO volumes to a maximum physical size of 16TB, and a maximum supported logical size of 160TB. This means that creating a VDO volume on a physical device that is larger than 16TB fails. To work around this issue, specify a larger slab size at VDO volume creation.
Clone Of:
: 1547675 (view as bug list)
Environment:
Last Closed: 2019-09-13 15:05:53 UTC
Embargoed:


Attachments (Terms of Use)

Description SATHEESARAN 2018-02-21 16:50:40 UTC
Description of problem:
-----------------------
VDO volumes comprises of slabs, with default slabsize of 2G.
Also there is known limitation of 8096 number of slabs available per VDO volume.
So 8096 x 2G = 16TB. In case the physical storage space exceeds 16TB, VDO volume creation fails.

So, in this case, the slab size should be increased to a value greater than 2G, and that will decrease the number of slabs.

Version-Release number of selected component (if applicable):
--------------------------------------------------------------
cockpit-ovirt-dashboard-0.11.11

How reproducible:
-----------------
Always

Steps to Reproduce:
-------------------
1. Start installation of RHHI 1.1, using 'Hosted Engine with Gluster' option
2. Have a disk with more than 16TB, for the creation of bricks
3. Enable dedupe & compression on that device

Actual results:
----------------
VDO volume creation fails with error 'Exceeds maximum number of slabs supported' when the device more than 16TB physical storage space is provided

Expected results:
-----------------
VDO volume creation should be successful even when the device with more than 16TB is used for bricks

In other case, cockpit-ovirt gluster plugin should have that intelligence to increase the slab size in that case when the physical storage space of the device is more than 16TB

Additional info:
----------------
I don't have much information about the effect of increasing the slabsize, it needs to be discussed with SME

Comment 1 Sahina Bose 2018-05-30 06:02:38 UTC
Moving this as we need to query disk size info to get the physical size to populate this

Comment 5 Gobinda Das 2018-07-24 06:37:59 UTC
Laura,
 Yes, it's correct.

Comment 6 SATHEESARAN 2019-09-13 15:05:53 UTC
This is already fixed with cockpit-ovirt logic, where when the size of the brick is more than 1 TB, then the slab size becomes 32G, else, 
the slab size is taken as 2GB

Tested with cockpit-ovirt-dashboard-0.12.2


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