Thanks once again Johan!
What would be your approach: JBOD straight or JBOD made of RAIDed bricks? Moacir ________________________________ From: Johan Bernhardsson <jo...@kafit.se> Sent: Tuesday, August 8, 2017 11:24 AM To: Moacir Ferreira; Devin Acosta; firstname.lastname@example.org Subject: Re: [ovirt-users] Good practices On ovirt gluster uses sharding. So all large files are broken up in small pieces on the gluster bricks. /Johan On August 8, 2017 12:19:39 Moacir Ferreira <moacirferre...@hotmail.com> wrote: Thanks Johan, you brought "light" into my darkness! I went looking for the GlusterFS tiering how-to and it looks like quite simple to attach a SSD as hot tier. For those willing to read about it, go here: http://blog.gluster.org/2016/03/automated-tiering-in-gluster/ Now, I still have a question: VMs are made of very large .qcow2 files. My understanding is that files in Gluster are kept all together in a single brick. If so, I will not benefit from tiering as a single SSD will not be big enough to fit all my large VM .qcow2 files. This would not be true if Gluster can store "blocks" of data that compose a large file spread on several bricks. But if I am not wrong, this is one of key differences in between GlusterFS and Ceph. Can you comment? Moacir ________________________________ From: Johan Bernhardsson <jo...@kafit.se> Sent: Tuesday, August 8, 2017 7:03 AM To: Moacir Ferreira; Devin Acosta; email@example.com Subject: Re: [ovirt-users] Good practices You attach the ssd as a hot tier with a gluster command. I don't think that gdeploy or ovirt gui can do it. The gluster docs and redhat docs explains tiering quite good. /Johan On August 8, 2017 07:06:42 Moacir Ferreira <moacirferre...@hotmail.com> wrote: Hi Devin, Please consider that for the OS I have a RAID 1. Now, lets say I use RAID 5 to assemble a single disk on each server. In this case, the SSD will not make any difference, right? I guess that to be possible to use it, the SSD should not be part of the RAID 5. In this case I could create a logical volume made of the RAIDed brick and then extend it using the SSD. I.e.: Using gdeploy: [disktype] jbod .... [pv1] action=create devices=sdb, sdc wipefs=yes ignore_vg_erros=no [vg1] action=create vgname=gluster_vg_jbod pvname=sdb ignore_vg_erros=no [vg2] action=extend vgname=gluster_vg_jbod pvname=sdc ignore_vg_erros=no But will Gluster be able to auto-detect and use this SSD brick for tiering? Do I have to do some other configurations? Also, as the VM files (.qcow2) are quite big will I benefit from tiering? This is wrong and my approach should be other? Thanks, Moacir ________________________________ From: Devin Acosta <de...@pabstatencio.com> Sent: Monday, August 7, 2017 7:46 AM To: Moacir Ferreira; firstname.lastname@example.org Subject: Re: [ovirt-users] Good practices Moacir, I have recently installed multiple Red Hat Virtualization hosts for several different companies, and have dealt with the Red Hat Support Team in depth about optimal configuration in regards to setting up GlusterFS most efficiently and I wanted to share with you what I learned. In general Red Hat Virtualization team frowns upon using each DISK of the system as just a JBOD, sure there is some protection by having the data replicated, however, the recommendation is to use RAID 6 (preferred) or RAID-5, or at least RAID-1 at the very least. Here is the direct quote from Red Hat when I asked about RAID and Bricks: "A typical Gluster configuration would use RAID underneath the bricks. RAID 6 is most typical as it gives you 2 disk failure protection, but RAID 5 could be used too. Once you have the RAIDed bricks, you'd then apply the desired replication on top of that. The most popular way of doing this would be distributed replicated with 2x replication. In general you'll get better performance with larger bricks. 12 drives is often a sweet spot. Another option would be to create a separate tier using all SSD’s.” In order to SSD tiering from my understanding you would need 1 x NVMe drive in each server, or 4 x SSD hot tier (it needs to be distributed, replicated for the hot tier if not using NVME). So with you only having 1 SSD drive in each server, I’d suggest maybe looking into the NVME option. Since your using only 3-servers, what I’d probably suggest is to do (2 Replicas + Arbiter Node), this setup actually doesn’t require the 3rd server to have big drives at all as it only stores meta-data about the files and not actually a full copy. Please see the attached document that was given to me by Red Hat to get more information on this. Hope this information helps you. -- Devin Acosta, RHCA, RHVCA Red Hat Certified Architect On August 6, 2017 at 7:29:29 PM, Moacir Ferreira (moacirferre...@hotmail.com<mailto:moacirferre...@hotmail.com>) wrote: I am willing to assemble a oVirt "pod", made of 3 servers, each with 2 CPU sockets of 12 cores, 256GB RAM, 7 HDD 10K, 1 SSD. The idea is to use GlusterFS to provide HA for the VMs. The 3 servers have a dual 40Gb NIC and a dual 10Gb NIC. So my intention is to create a loop like a server triangle using the 40Gb NICs for virtualization files (VMs .qcow2) access and to move VMs around the pod (east /west traffic) while using the 10Gb interfaces for giving services to the outside world (north/south traffic). This said, my first question is: How should I deploy GlusterFS in such oVirt scenario? My questions are: 1 - Should I create 3 RAID (i.e.: RAID 5), one on each oVirt node, and then create a GlusterFS using them? 2 - Instead, should I create a JBOD array made of all server's disks? 3 - What is the best Gluster configuration to provide for HA while not consuming too much disk space? 4 - Does a oVirt hypervisor pod like I am planning to build, and the virtualization environment, benefits from tiering when using a SSD disk? And yes, will Gluster do it by default or I have to configure it to do so? At the bottom line, what is the good practice for using GlusterFS in small pods for enterprises? You opinion/feedback will be really appreciated! Moacir _______________________________________________ Users mailing list Users@ovirt.org<mailto:Users@ovirt.org> http://lists.ovirt.org/mailman/listinfo/users _______________________________________________ Users mailing list Users@ovirt.org<mailto:Users%40ovirt.org> http://lists.ovirt.org/mailman/listinfo/users
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