Hi Salvatore, We've done this before (non-shared metadata NSDs with GPFS 4.1) and noted these constraints:
* Filesystem descriptor quorum: since it will be easier to have a metadata disk go offline, it's even more important to have three failure groups with FusionIO metadata NSDs in two, and at least a desc_only NSD in the third one. You may even want to explore having three full metadata replicas on FusionIO. (Or perhaps if your workload can tolerate it the third one can be slower but in another GPFS "subnet" so that it isn't used for reads.) * Make sure to set the correct default metadata replicas in your filesystem, corresponding to the number of metadata failure groups you set up. When a metadata server goes offline, it will take the metadata disks with it, and you want a replica of the metadata to be available. * When a metadata server goes offline and comes back up (after a maintenance reboot, for example), the non-shared metadata disks will be stopped. Until those are brought back into a well-known replicated state, you are at risk of a cluster-wide filesystem unmount if there is a subsequent metadata disk failure. But GPFS will continue to work, by default, allowing reads and writes against the remaining metadata replica. You must detect that disks are stopped (e.g. mmlsdisk) and restart them (e.g. with mmchdisk <fs> start –a). I haven't seen anyone "recommend" running non-shared disk like this, and I wouldn't do this for things which can't afford to go offline unexpectedly and require a little more operational attention. But it does appear to work. Thx Paul Sanchez From: [email protected] [mailto:[email protected]] On Behalf Of Salvatore Di Nardo Sent: Thursday, October 09, 2014 8:03 AM To: gpfsug main discussion list Subject: [gpfsug-discuss] metadata vdisks on fusionio.. doable? Hello everyone, Suppose we want to build a new GPFS storage using SAN attached storages, but instead to put metadata in a shared storage, we want to use FusionIO PCI cards locally on the servers to speed up metadata operation( http://www.fusionio.com/products/iodrive) and for reliability, replicate the metadata in all the servers, will this work in case of server failure? To make it more clear: If a server fail i will loose also a metadata vdisk. Its the replica mechanism its reliable enough to avoid metadata corruption and loss of data? Thanks in advance Salvatore Di Nardo
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