Hi,
I would say this is normal. 1GB of ram per 1TB is what we designed the cluster for, I would believe that an EC-pool demands a lot more. Buy more ram and start everything 32GB ram is quite little, when the cluster is operating OK you'll see that extra ram getting used as file cache which makes the cluster faster.
Regards,
Josef
On 6 Jan 2016 12:12, "Kenneth Waegeman" <kenneth.waegeman@xxxxxxxx> wrote:
Hi all,
We experienced some serious trouble with our cluster: A running cluster started failing and started a chain reaction until the ceph cluster was down, as about half the OSDs are down (in a EC pool)
Each host has 8 OSDS of 8 TB (i.e. RAID 0 of 2 4TB disk) for an EC pool (10+3, 14 hosts) and 2 cache OSDS and 32 GB of RAM.
The reason we have the Raid0 of the disks, is because we tried with 16 disk before, but 32GB didn't seem enough to keep the cluster stable
We don't know for sure what triggered the chain reaction, but what we certainly see, is that while recovering, our OSDS are using a lot of memory. We've seen some OSDS using almost 8GB of RAM (resident; virtual 11GB)
So right now we don't have enough memory to recover the cluster, because the OSDS get killed by OOMkiller before they can recover..
And I don't know doubling our memory will be enough..
A few questions:
* Does someone has seen this before?
* 2GB was still normal, but 8GB seems a lot, is this expected behaviour?
* We didn't see this with an nearly empty cluster. Now it was filled about 1/4 (270TB). I guess it would become worse when filled half or more?
* How high can this memory usage become ? Can we calculate the maximum memory of an OSD? Can we limit it ?
* We can upgrade/reinstall to infernalis, will that solve anything?
This is related to a previous post of me : http://permalink.gmane.org/gmane.comp.file-systems.ceph.user/22259
Thank you very much !!
Kenneth
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