Can't tell you, I only use gluster for VM disks. The heal will hammer performances pretty bad, but that really depends on what you do, so I'd say test it a bunch and use whatever works best.
I think they advise for a high value to make sure you don't have two nodes marked down in cose succession, which could either cause a split-brain or make your volume readonly for a while, depending on your config and number of nodes. On Wed, Dec 27, 2017 at 11:17:01AM +0000, Omar Kohl wrote: > Hi, > > > If you set it to 10 seconds, and a node goes down, you'll see a 10 seconds > > freez in all I/O for the volume. > > Exactly! ONLY 10 seconds instead of the default 42 seconds :-) > > As I said before the problem with the 42 seconds is that a Windows Samba > Client will disconnect (and therefore interrupt any read/write operation) > after waiting for about 25 seconds. So 42 seconds is too high. In this case > it would therefore make more sense to reduce the ping-timeout, right? > > Has anyone done any performance measurements on what the implications of a > low ping-timeout are? What are the costs of "triggering heals all the time"? > > On a related note I found the extras/hook-scripts/start/post/S29CTDBsetup.sh > script that mounts a CTDB (Samba) share and explicitly sets the ping-timeout > to 10 seconds. There is a comment saying: "Make sure ping-timeout is not > default for CTDB volume". Unfortunately there is no explanation in the > script, in the commit or in the Gerrit review history > (https://review.gluster.org/#/c/7569/, https://review.gluster.org/#/c/8007/) > for WHY you make sure ping-timeout is not default. Can anyone tell me the > reason? > > Kind regards, > Omar > > -----Ursprüngliche Nachricht----- > Von: [email protected] > [mailto:[email protected]] Im Auftrag von [email protected] > Gesendet: Dienstag, 26. Dezember 2017 22:05 > An: [email protected] > Betreff: Re: [Gluster-users] Exact purpose of network.ping-timeout > > Hi, > > It's just the delay for which a node can stop responding before being marked > as down. > Basically that's how long a node can go down before a heal becomes necessary > to bring it back. > > If you set it to 10 seconds, and a node goes down, you'll see a 10 seconds > freez in all I/O for the volume. That's why you don't want it too high > (having a 2 minutes freez on I/O for example would be pretty bad, depending > on what you host), but you don't want it too low either (to avoid triggering > heals all the time). > > You can configure it because it depends on what you host. You might be okay > with a few minutes freez to avoid a heal, or you might not care about heals > at all and prefer a very low value to avoid feezes. > The default value should work pretty well for most things though > > On Tue, Dec 26, 2017 at 01:11:48PM +0000, Omar Kohl wrote: > > Hi, > > > > I have a question regarding the "ping-timeout" option. I have been > > researching its purpose for a few days and it is not completely clear to > > me. Especially that it is apparently strongly encouraged by the Gluster > > community not to change or at least decrease this value! > > > > Assuming that I set ping-timeout to 10 seconds (instead of the default 42) > > this would mean that if I have a network outage of 11 seconds then Gluster > > internally would have to re-allocate some resources that it freed after the > > 10 seconds, correct? But apart from that there are no negative > > implications, are there? For instance if I'm copying files during the > > network outage then those files will continue copying after those 11 > > seconds. > > > > This means that the only purpose of ping-timeout is to save those extra > > resources that are used by "short" network outages. Is that correct? > > > > If I am confident that my network will not have many 11 second outages and > > if they do occur I am willing to incur those extra costs due to resource > > allocation is there any reason not to set ping-timeout to 10 seconds? > > > > The problem I have with a long ping-timeout is that the Windows Samba > > Client disconnects after 25 seconds. So if one of the nodes of a Gluster > > cluster shuts down ungracefully then the Samba Client disconnects and the > > file that was being copied is incomplete on the server. These "costs" seem > > to be much higher than the potential costs of those Gluster resource > > re-allocations. But it is hard to estimate because there is not clear > > documentation what exactly those Gluster costs are. > > > > In general I would be very interested in a comprehensive explanation of > > ping-timeout and the up- and downsides of setting high or low values for it. > > > > Kinds regards, > > Omar > > _______________________________________________ > > Gluster-users mailing list > > [email protected] > > http://lists.gluster.org/mailman/listinfo/gluster-users > _______________________________________________ > Gluster-users mailing list > [email protected] > http://lists.gluster.org/mailman/listinfo/gluster-users
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