<div dir="ltr"><div dir="ltr"><div>Thanks Strahil,</div><div><br></div><div>in this link <a href="https://access.redhat.com/documentation/en-us/red_hat_gluster_storage/3.4/html/administration_guide/sect-creating_replicated_volumes">https://access.redhat.com/documentation/en-us/red_hat_gluster_storage/3.4/html/administration_guide/sect-creating_replicated_volumes</a> i see:</div><div><br></div><div><i>Sharding has one supported use case: in the context of providing Red Hat
Gluster Storage as a storage domain for Red Hat Enterprise
Virtualization, to provide storage for live virtual machine images. Note
that sharding is also a requirement for this use case, as it provides
significant performance improvements over previous implementations. <br></i></div><div><i><br></i></div><div>The deafult setting in GusterFS 6.1 appears to be:</div> <br><div>features.shard-block-size 64MB <br>features.shard-lru-limit 16384 <br>features.shard-deletion-rate 100 <br></div><div><br></div><div>Bricks in my case are over an xfs filesystem. I'll try different block-size but if I understand correctly, small block sizes are preferable to big block sizes and If i have doubt I will put 4M.</div><div><br></div><div>Very thanks for the warning, message received! :-)</div><div><br></div><div>Best Regards,</div><div><br></div><div>Cristian<br></div><div><br></div><div></div><div><i></i></div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">Il giorno gio 20 giu 2019 alle ore 22:13 Strahil Nikolov <<a href="mailto:hunter86_bg@yahoo.com">hunter86_bg@yahoo.com</a>> ha scritto:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div><div class="gmail-m_-4360627142264084429ydp678665a5yahoo-style-wrap" style="font-family:courier new,courier,monaco,monospace,sans-serif;font-size:16px"><div></div>
<div>Sharding is complex. It helps to heal faster -as only the shards that got changed will be replicated, but imagine a 1GB shard that got only 512k updated - in such case you will copy the whole shard to the other replicas.</div><div>RHV & oVirt use a default shard size of 4M which is the exact size of the default PE in LVM.</div><div><br></div><div>On the other side, it speeds stuff as gluster can balance the shards properly on the replicas and thus you can evenly distribute the load on the cluster.</div><div>It is not a coincidence that RHV and oVirt use sharding by default.</div><div><br></div><div>Just a warning.</div><div>NEVER, EVER, DISABLE SHARDING!!! ONCE ENABLED - STAYS ENABLED!</div><div>Don't ask how I learnGrazie dell'avviso, messaggio ricevuto!t that :)</div><div><br></div><div>Best Regards,</div><div>Strahil Nikolov</div><div><br></div><div><br></div><div><br></div>
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В четвъртък, 20 юни 2019 г., 18:32:00 ч. Гринуич+3, Cristian Del Carlo <<a href="mailto:cristian.delcarlo@targetsolutions.it" target="_blank">cristian.delcarlo@targetsolutions.it</a>> написа:
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<div><div id="gmail-m_-4360627142264084429ydp93be247yiv2327294799"><div><div dir="ltr"><div>Hi,</div><div><br clear="none"></div><div>thanks for your help.</div><div><br clear="none"></div><div>I am planing to use libvirtd with plain KVM.</div><div><br clear="none"></div><div>Ok i will use libgfapi. <br clear="none"></div><div><br clear="none"></div><div>I'm confused about the use of sharding is it useful in this configuration? Doesn't sharding help limit the bandwidth in the event of a rebalancing?</div><div><br clear="none"></div><div>In the vm setting so i need to use directsync to avoid corruption.</div><div><br clear="none"></div><div>Thanks again,<br clear="none"> </div></div><br clear="none"><div class="gmail-m_-4360627142264084429ydp93be247yiv2327294799gmail_quote"><div class="gmail-m_-4360627142264084429ydp93be247yiv2327294799gmail_attr" dir="ltr">Il giorno gio 20 giu 2019 alle ore 12:25 Strahil <<a shape="rect" href="mailto:hunter86_bg@yahoo.com" rel="nofollow" target="_blank">hunter86_bg@yahoo.com</a>> ha scritto:<br clear="none"></div><div class="gmail-m_-4360627142264084429ydp93be247yiv2327294799yqt4291059422" id="gmail-m_-4360627142264084429ydp93be247yiv2327294799yqt39338"><blockquote class="gmail-m_-4360627142264084429ydp93be247yiv2327294799gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><p dir="ltr">Hi,</p>
<p dir="ltr">Are you planing to use oVirt or plain KVM or openstack?</p>
<p dir="ltr">I would recommend you to use gluster v6.1 as it is the latest stable version and will have longer support than the older versions.</p>
<p dir="ltr">Fuse vs libgfapi - use the latter as it has better performance and less overhead on the host.oVirt does supports both libgfapi and fuse.</p>
<p dir="ltr">Also, use replica 3 because you will have better read performance compared to replica 2 arbiter 1.</p>
<p dir="ltr">Sharding is a tradeoff between CPU (when there is no sharding , gluster shd must calculate the offset of the VM disk) and bandwidth (whole shard is being replicated despite even 512 need to be synced).</p>
<p dir="ltr">If you will do live migration - you do not want to cache in order to avoid corruption.<br clear="none">
Thus oVirt is using direct I/O.<br clear="none">
Still, you can check the gluster settings mentioned in Red Hat documentation for Virt/openStack .</p>
<p dir="ltr">Best Regards,<br clear="none">
Strahil Nikolov</p>
<div class="gmail-m_-4360627142264084429ydp93be247yiv2327294799gmail-m_1444675035890430144quote">On Jun 20, 2019 13:12, Cristian Del Carlo <<a shape="rect" href="mailto:cristian.delcarlo@targetsolutions.it" rel="nofollow" target="_blank">cristian.delcarlo@targetsolutions.it</a>> wrote:<br clear="none"><blockquote class="gmail-m_-4360627142264084429ydp93be247yiv2327294799gmail-m_1444675035890430144quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex"><div dir="ltr"><div>Hi,</div><br clear="none">I'm testing glusterfs before using it in production, it should be used to store vm for nodes with libvirtd.<br clear="none"><br clear="none"><div>In production I will have 4 nodes connected with a dedicated 20gbit/s network.</div><div><br clear="none"></div><div>Which version to use in production on a centos 7.x? Should I use Gluster version 6?</div><div><br clear="none"></div><div>To make the volume available to libvirtd the best method is to use FUSE?</div><div><br clear="none"></div><div>I see that stripped is deprecated. Is it reasonable to use the volume with 3 replicas on 4 nodes and sharding enabled? <br clear="none"></div><div></div><div>Is there convenience to use sharding volume in this context? I think could positive inpact in read performance or rebalance. Is it true?<br clear="none"></div><div><br clear="none"></div>In the vm configuration I use the virtio disk. How is it better to set the disk cache to get the best performances none, default or writeback?<div><br clear="none">Thanks in advance for your patience and answers.</div><div><br clear="none"></div><div>Thanks,<br clear="none"></div><div><div dir="ltr"><div dir="ltr"><div><br clear="none"></div><div><b><font color="#990000"><i><br clear="none"></i></font></b></div><div><b><font color="#990000"><i>Cristian Del Carlo</i></font></b><br clear="none"></div><div></div></div></div></div></div>
</blockquote></div></blockquote></div></div><br clear="all"><br clear="none">-- <br clear="none"><div class="gmail-m_-4360627142264084429ydp93be247yiv2327294799gmail_signature" dir="ltr"><div dir="ltr"><div><span></span><span></span><br clear="none"></div><div><font><b><font color="#990000"><i><br clear="none"></i></font></b></font></div><div><font><b><font color="#990000"><i>Cristian Del Carlo</i></font></b><br clear="none"></font></div><div></div><div><i><font>Target Solutions s.r.l.<br clear="none"></font></i></div><div><i><font><br clear="none"></font></i></div>
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