On Wed, Jul 6, 2016 at 2:27 PM, Nir Soffer <[email protected]> wrote:
> On Wed, Jul 6, 2016 at 12:18 AM, David Twersky <[email protected]> > wrote: > > We use a lot of flash arrays, and some of them require that devices be 4k > > aligned, is it possible to create a Fibre Channel Storage Domain and > have it > > 4k aligned? > Is it required or preferred? Because while most of our data is 4K aligned, some writes aren't - mainly metadata of the storage domain. So you won't be usually suffering from mis-aligned writes (or reads) which are costly, but we must be able to perform atomic 512b writes (which may translate to a read-modify-write of course in the flash). I'm not sure what we expose to VMs, btw - if we can expose to them 4K drive...? > I don't think we support this. > Indeed - we assume sector size to be 512b in the code: lib/vdsm/storage/constants.py:SECTOR_SIZE = 512 Can you use a direct LUN, though? Y. > > For example, we assume that writing 512 bytes blocks is atomic, if these > writes will fail because the minimal block is 4k, block storage metadata > operations will fail. > > Anyway, why not try to add such lun and create a storage domain for > testing? > > Nir > _______________________________________________ > Users mailing list > [email protected] > http://lists.ovirt.org/mailman/listinfo/users >
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