[Gluster-users] State of Gluster project

[Strahil Nikolov]

На 20 юни 2020 г. 19:08:49 GMT+03:00, Gionatan Danti <g.danti at assyoma.it> написа:
>DISCLAIMER: I *really* appreciate this project and I thank all peoples 
>involved.
>
>Il 2020-06-19 21:33 Mahdi Adnan ha scritto:
>> The strength of Gluster, in my opinion, is the simplicity of creating
>> distributed volumes that can be consumed by different clients, and
>> this is why we chose Gluster back in 2016 as our main VMs Storage
>> backend for VMWare and oVirt.
>
>I absolutely agree on that: it is very simple to create replicated and 
>distributed storage with Gluster. This is a key Gluster feature: last 
>time I checked Ceph, it basically required 6+ machines and a small team
>
>managing them. I read it is much easier now, but I doubt it is as easy 
>as Gluster.
>
>This is the main reason why I periodically reconsider Gluster as a 
>backend for hyperconverged virtual machines (coupled with the metadata 
>server-less approach). Sadly, I arrive each time at the same
>conclusion: 
>do not run Gluster in critical production environment without RedHat 
>support and stable release, as Red Hat Gluster Storage is.
>
>Maybe I am overcautious, but I find too easy to end with split brain 
>scenario, sometime even by simply rebooting a node at the wrong moment.
>
>The needing to enable sharding for efficient virtual disk healing
>scares 
>me: if gluster fails, I need to reconstruct the disk images from each 
>chunk with a tedious, time-and-space consuming process.

The efforts are  far less than reconstructing the disk of a VM from CEPH. In gluster , just run a find on the brick  searching for the name of the VM disk and you will find the VM_IMAGE.xyz  (where xyz is just a number)  and then concatenate the  list into a single file.

>Moreover, from a cursory view of Gluster's and other mailing lists, 
>Qemu/KVM gfapi backend seems somewhat less stable than a FUSE gluster 
>mount, and FUSE is not so fast either. Is my impression wrong?

That's  true,  but  you  could  also  use  NFS Ganesha,  which  is more  performant  than FUSE and also as  reliable  as  it.

>I really have the fealing that Gluster is good at a diametrically 
>opposed scenario: scale-out NAS, for which it was conceived many moons 
>ago. And RedHat backing on Ceph right now for block storage let me
>think 
>Gluster issues with virtual disks were noticed by many.
>
>> We suffered "and still" from performance issues with Gluster on use
>> cases related to small files, but Gluster as a storage backend for
>> Virtual Machines is really performant.
>
>I have mixed feelings about Gluster performance. In the past[1] I 
>measured ~500 max IOPs for synchronous 4K writes per brick, which is a 
>lot for a single disk, less so for a RAID array or SSD. Aggregated 
>performance scaled linearly with increasing brick count, so maybe the 
>solution is to simply go full-Gluster and ditch RAID, but replacing a 
>disk in Gluster is much less convenient that doing the same with a RAID
>
>array (both hardware and software RAID) or ZFS.

It's  not so hard to  do it  -  just  use  either  'reset-brick' or  'replace-brick' .

>Note that I am not implying that Ceph is faster; rather, than a small 
>Gluster setup with few brick can be slower than expected.
>
>I would love to ear other opinions and on-the-field experiences.
>Thanks.
>
>[1] 
>https://lists.gluster.org/pipermail/gluster-users/2020-January/037607.html

Best Regards,
Strahil Nikolov