[ ... ] >> are USB drives really that unreliable [ ... ] [ ... ] > There are similar SATA chips too (occasionally JMicron and > Marvell for example are somewhat less awesome than they could > be), and practically all Firewire bridge chips of old "lied" a > lot [ ... ] > That plus Btrfs is designed to work on top of a "well defined" > block device abstraction that is assumed to "work correctly" > (except for data corruption), [ ... ]
When I insist on the reminder that Btrfs is designed to use the block-device protocol and state machine, rather than USB and SATA devices, it is because that makes more explicit that the various layer between the USB and SATA device can "lie" too, including for example the Linux page cache which is just below the block-device layer. But also the disk scheduler, the SCSI protocol handler, the USB and SATA drivers and disk drivers, the PCIe chipset, the USB or SATA host bus adapter, the cable, the backplane. This paper reports the results of some testing of "enterprise grade" storage systems at CERN, and some of the symptoms imply that "lies" can happen *anywhere*. It is scary. It supports having data checksumming in the filesystem, a rather extreme choice. -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
