On 29.12.2013 19:55, Stan Hoeppner wrote: > On 12/29/2013 3:50 AM, Dave Chinner wrote: > ... > > I think you are forgetting that developer time is *expensive* and > > *scarce*. This is essentially a solved problem: An SSD in a USB3 > > enclosure as a temporary swap device is by far the most cost > > effective way to make repair scale to arbitrary amounts of metadata. > > It certainly scales far better than developer time and testing > > resources... > > Now this is an interesting idea Dave. I hadn't considered temporary > swap. Would USB be reliable enough for this? I've seen lots problem > reports with folks using USB storage with Linux, random disconnections > and what not. It's certainly a problem with several variables. - Quality of USB-Stack (should be quite good nowadays, but there can always be (new) bugs) - Quality of SATA <-> USB(3) Chip - Quality of SSD itself And with Quality i mean everything from physical chip up to firmware. I'm not quite sure what happens when SWAP crapps out. I think it can be everything from "machine goes dead" down to "all programs with pages in swap are terminated". I've transfert quite a few TB over USB3 and i can say, it mostly works. But random disconnects happen and you can't really be sure which part is the problem as it only happens rarely. For e.g. currently i have a HDD that randomly but seldomly craps out in an USB3 enclosure, after coping a few hundert GB. The drive works flawlessly when connected directly by SATA to a (different) computer, at least i haven't had a failure after i moved the drive. Is it the drive, chip in enclose, firmware between HDD & enclosure not playing nice (like too high command timeouts on HDD side and too low on enclosure-sde), USB3 stack. Can't really tell. So: I would consides SWAP on a device connected via USB3 to be on the risky side. I would validate beforehand if that specific combination of xhci/enclosure chip/SSD survies a prolonged time of "high I/O stress". Like several days of full bandwidth/random I/O. -- Matthias _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
