2017-06-12 10:49 GMT+02:00 Burkhard Linke < [email protected]>:
> Hi, > > > On 06/12/2017 10:31 AM, Daniel Carrasco wrote: > >> Hello, >> >> I'm very new on Ceph, so maybe this question is a noob question. >> >> We have an architecture that have some web servers (nginx, php...) with a >> common File Server through NFS. Of course that is a SPOF, so we want to >> create a multi FS to avoid future problems. >> >> We've already tested GlusterFS, but is very slow reading small files >> using the oficial client (from 600ms to 1700ms to read the Doc page), and >> through NFS Ganesha it fails a lot (permissions errors, 404 when the file >> exists...). >> The next we're trying is Ceph that looks very well and have a good >> performance even with small files (near to NFS performance: 90-100ms to >> 100-120ms), but on some tests that I've done, it stop working when an OSD >> is down. >> >> My test architecture are two servers with one OSD and one MON each, and a >> third with a MON and an MDS. I've configured the cluster to have two copies >> of every PG (just like a RAID1) and all looks fine (health OK, three >> monitors...). >> My test client also works fine: it connects to the cluster and is able to >> server the webpage without problems, but my problems comes when an OSD goes >> down. The cluster detects that is down, it shows like needs more OSD to >> keep the two copies, designates a new MON and looks like is working, but >> the client is unable to receive new files until I power on the OSD again >> (it happens with both OSD). >> >> My question is: Is there any way to say Ceph to keep serving files even >> when an OSD is down? >> > > I assume the data pool is configured with size=2 and min_size=2. This > means that you need two active replicates to allow I/O to a PG. With one > OSD down this requirement cannot be met. > > You can either: > - add a third OSD > - set min_size=1 > The later might be fine for test setup, but do not run this configuration > in production. NEVER. EVER. Search the mailing list for more details. Thanks!! , just what I thought, a noob question hehe. Now is working. I'll search later in list, but looks like is to avoid split brain or similar. > > > > >> >> My other question is about MDS: >> Multi-MDS enviorement is stable?, because if I have multiple FS to avoid >> SPOF and I only can deploy an MDS, then we have a new SPOF... >> This is to know if maybe i need to use Block Devices pools instead File >> Server pools. >> > > AFAIK active/active MDS setups are still considered experimental; > active/standby(-replay) is a supported setup. We currently use one active > and one standby-replay MDS for our CephFS instance serving several million > files. > > Failover between the MDS works, but might run into problems with a large > number of open files (each requiring a stat operation). Depending on the > number of open files failover takes some seconds up to 5-10 minutes in our > setup. > Thanks again for your response, Is not for performance purporse so an active/standby will be enough. I'll search about this configuration. About time, always is better to keep the page down for some seconds instead wait for an admin to fix it. > > Regards, > Burkhard Linke > > > _______________________________________________ > ceph-users mailing list > [email protected] > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > Greetings!! -- _________________________________________ Daniel Carrasco Marín Ingeniería para la Innovación i2TIC, S.L. Tlf: +34 911 12 32 84 Ext: 223 www.i2tic.com _________________________________________
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