Hello Brent, no, swap is definitely not needed if you configure systems correctly. Swap in Ceph kills all your performance and brings a lot of harm to clusters. It increases the downtime, decreases the performance and can result in much longer recovery times which endangers your data. In the very old times, swap was required as you were unable to have enough memory in your systems. Today's server does not require a swap partition and I personally disable it on all my systems in the past >10y. As my last company was a datacenter provider with multiple thousand systems, I believe to have quite some insights if that is stable. What happens if you run out of memory you might ask? - simple, OOM killer kills one process and systemd restarts it, service is back up in a few seconds. Can you choose what process is killed most likely? - yes you can. Take a look into /proc/*/oom_adj What happens if I swap gets filled up? - total destruction ;), your OOM killer kills one process, freeing up swap takes a much longer time, system load skyrocks, services become unresponsive, Ceph client IO can drop to near zero... just save yourself the trouble. So yes, we strongly believe to have a far superior system by design by just preventing swap at all. -- Martin Verges Managing director Mobile: +49 174 9335695 E-Mail: martin.verges@xxxxxxxx Chat: https://t.me/MartinVerges croit GmbH, Freseniusstr. 31h, 81247 Munich CEO: Martin Verges - VAT-ID: DE310638492 Com. register: Amtsgericht Munich HRB 231263 Web: https://croit.io YouTube: https://goo.gl/PGE1Bx Am So., 5. Apr. 2020 um 01:59 Uhr schrieb Brent Kennedy <bkennedy@xxxxxxxxxx >: > Forgive me for asking but it seems most OS's require a swap file and when > I look into doing something similar(meaning not having anything), they all > say the OS could go unstable without it. It seems that anyone doing this > needs to be 100 certain memory will not be used at 100% ever or the OS > would crash if no swap was there. How are you getting around this and has > it ever been a thing? > > Also, for the ceph OSDs, where are you storing the osd and host > configurations ( central storage? )? > > Regards, > -Brent > > Existing Clusters: > Test: Nautilus 14.2.2 with 3 osd servers, 1 mon/man, 1 gateway, 2 iscsi > gateways ( all virtual on nvme ) > US Production(HDD): Nautilus 14.2.2 with 11 osd servers, 3 mons, 4 > gateways, 2 iscsi gateways > UK Production(HDD): Nautilus 14.2.2 with 12 osd servers, 3 mons, 4 gateways > US Production(SSD): Nautilus 14.2.2 with 6 osd servers, 3 mons, 3 > gateways, 2 iscsi gateways > > > > > -----Original Message----- > From: Martin Verges <martin.verges@xxxxxxxx> > Sent: Sunday, March 22, 2020 3:50 PM > To: huxiaoyu@xxxxxxxxxxxx > Cc: ceph-users <ceph-users@xxxxxxx> > Subject: Re: Questions on Ceph cluster without OS disks > > Hello Samuel, > > we from croit.io don't use NFS to boot up Servers. We copy the OS > directly into the RAM (approximately 0.5-1GB). Think of it like a > container, you start it and throw it away when you no longer need it. > This way we can save the slots of OS harddisks to add more storage per > node and reduce overall costs as 1GB ram is cheaper then an OS disk and > consumes less power. > > If our management node is down, nothing will happen to the cluster. No > impact, no downtime. However, you do need the mgmt node to boot up the > cluster. So after a very rare total power outage, your first system would > be the mgmt node and then the cluster itself. But again, if you configure > your systems correct, no manual work is required to recover from that. For > everything else, it is possible (but definitely not needed) to deploy our > mgmt node in active/passive HA. > > We have multiple hundred installations worldwide in production > environments. Our strong PXE knowledge comes from more than 20 years of > datacenter hosting experience and it never ever failed us in the last >10 > years. > > The main benefits out of that: > - Immutable OS freshly booted: Every host has exactly the same version, > same library, kernel, Ceph versions,... > - OS is heavily tested by us: Every croit deployment has exactly the same > image. We can find errors much faster and hit much fewer errors. > - Easy Update: Updating OS, Ceph or anything else is just a node reboot. > No cluster downtime, No service Impact, full automatic handling by our > mgmt Software. > - No need to install OS: No maintenance costs, no labor required, no > other OS management required. > - Centralized Logs/Stats: As it is booted in memory, all logs and > statistics are collected on a central place for easy access. > - Easy to scale: It doesn't matter if you boot 3 oder 300 nodes, all boot > the exact same image in a few seconds. > .. lots more > > Please do not hesitate to contact us directly. We always try to offer an > excellent service and are strongly customer oriented. > > -- > Martin Verges > Managing director > > Mobile: +49 174 9335695 > E-Mail: martin.verges@xxxxxxxx > Chat: https://t.me/MartinVerges > > croit GmbH, Freseniusstr. 31h, 81247 Munich > CEO: Martin Verges - VAT-ID: DE310638492 Com. register: Amtsgericht Munich > HRB 231263 > > Web: https://croit.io > YouTube: https://goo.gl/PGE1Bx > > > Am Sa., 21. März 2020 um 13:53 Uhr schrieb huxiaoyu@xxxxxxxxxxxx < > huxiaoyu@xxxxxxxxxxxx>: > > > Hello， Martin， > > > > I notice that Croit advocate the use of ceph cluster without OS disks, > > but with PXE boot. > > > > Do you use a NFS server to serve the root file system for each node? > > such as hosting configuration files, user and password, log files, > > etc. My question is, will the NFS server be a single point of failure? > > If the NFS server goes down, the network experience any outage, ceph > > nodes may not be able to write to the local file systems, possibly > leading to service outage. > > > > How do you deal with the above potential issues in production? I am a > > bit worried... > > > > best regards, > > > > samuel > > > > > > > > > > ------------------------------ > > huxiaoyu@xxxxxxxxxxxx > > > > > > > _______________________________________________ > ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an > email to ceph-users-leave@xxxxxxx > > _______________________________________________ ceph-users mailing list -- ceph-users@xxxxxxx To unsubscribe send an email to ceph-users-leave@xxxxxxx
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