Bug 1293634

Description of problem:
=======================

Executed a case on normalvolume(4x2) and Tiered volume (HT: 2x2, CT:2x2). The time taken to complete the sync when it is tiered volume is 2-4 times more than the normal volume. 

Note: In both these cases total subvolumes are 4 and no promotion/demotions ever happened. Slave volume in both these cases was 4x2

Normal Volume: 4x2
==================

> Time at which I started creating Data: 04:53:33
> Time at which it completed creation of Data: 05:05:42
> Time at which the used size of master and slave volume became equal: 05:09:12
> Sleep 2 mins
> Calculate arequal: It matches between master and slave @ 5:20:53 {Arequal checksum took ~7 mins to finish}

Total Time Taken to complete this test from data creation on master to matchin arequal checksum at slave: ~30min

Tiered Volume: HT: 2x2 and CT: 2x2
==================================

> Time at which I started creating Data: 05:29:31
> Time at which it completed creation of Data: 05:51:04
> Time at which the used size of master and slave volume became equal: 06:09:20
> Sleep 2 mins
> Calculate arequal: It matches between master and slave @ 06:19:40 {Arequal checksum took ~8 mins to finish}

Total Time Taken to complete this test from data creation on master to arequal checksum match at slave: ~50min

Data For reference:
===================

<i> for i in {1..5}; do dd if=/dev/zero of=dd.$i bs=2M count=1024; done
<ii> for i in {1..5}; do cp -rf /etc etc.$i ; done

Can not confirm the exact percentage of degradation in syncing because with tiered volume the creation in itself has performance degradation. During creation the rsync can still happen to slave.

So in general from data creation to sync in normal volume took approx: 16 mins vs 40 mins with tiered volume


[root@localhost scripts]# gluster volume rebal master tier status
Node                 Promoted files       Demoted files        Status              
---------            ---------            ---------            ---------           
localhost            0                    0                    in progress         
10.70.46.97          0                    0                    in progress         
10.70.46.93          0                    0                    in progress         
10.70.46.154         0                    0                    in progress         
Tiering Migration Functionality: master: success
[root@localhost scripts]# 


Version-Release number of selected component (if applicable):
=============================================================

glusterfs-3.7.5-12.el7rhgs.x86_64


How reproducible:
=================

Always