Messages in this thread | | | Date | Wed, 11 Jul 2007 11:49:57 +0900 | From | Tejun Heo <> | Subject | Re: [dm-devel] Re: [RFD] BIO_RW_BARRIER - what it means for devices, filesystems, and dm/md. |
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Valdis.Kletnieks@vt.edu wrote: > On Tue, 10 Jul 2007 14:39:41 EDT, Ric Wheeler said: > >> All of the high end arrays have non-volatile cache (read, on power loss, it is a >> promise that it will get all of your data out to permanent storage). You don't >> need to ask this kind of array to drain the cache. In fact, it might just ignore >> you if you send it that kind of request ;-) > > OK, I'll bite - how does the kernel know whether the other end of that > fiberchannel cable is attached to a DMX-3 or to some no-name product that > may not have the same assurances? Is there a "I'm a high-end array" bit > in the sense data that I'm unaware of?
Well, the array just has to tell the kernel that it doesn't to write back caching. The kernel automatically selects ORDERED_DRAIN in such case.
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