Messages in this thread | | | Date | Wed, 11 Jul 2007 18:44:21 -0400 | From | Ric Wheeler <> | Subject | Re: [dm-devel] Re: [RFD] BIO_RW_BARRIER - what it means for devices, filesystems, and dm/md. |
| |
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? >
There are ways to query devices (think of hdparm -I in S-ATA/P-ATA drives, SCSI has similar queries) to see what kind of device you are talking to. I am not sure it is worth the trouble to do any automatic detection/handling of this.
In this specific case, it is more a case of when you attach a high end (or mid-tier) device to a server, you should configure it without barriers for its exported LUNs.
ric - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |