How can I identify the request queue for a linux block device
Queue = blk_init_queue(sbd_request, &Device.lock);
block-device
Is DRBD the only viable block replication solution for Linux?
Yes, DRBD is the only replicated block device out there that can handle concurrent writes. If you plan to put a filesystem on top, it obviously needs to handle multiple writers as well, like GFS(2) and OCFS(2) do. Please note that if you can afford higher levels of abstraction for redundancy, you’ll likely be much, … Read more
Why is there both character device and block device for nvme?
The character device /dev/nvme0 is the NVME device controller, and block devices like /dev/nvme0n1 are the NVME storage namespaces: the devices you use for actual storage, which will behave essentially as disks. In enterprise-grade hardware, there might be support for several namespaces, thin provisioning within namespaces and other features. For now, you could think namespaces … Read more
Readahead Settings for LVM, Device-Mapper, Software Raid and Block Devices – what wins?
How does the RA setting get passed down the virtual block device chain? It depends. Let’s assume you are inside Xen domU and have RA=256. Your /dev/xvda1 is actual LV on the dom0 visible under /dev/dm1. So you have RA(domU(/dev/xvda1)) = 256 and RA(dom0(/dev/dm1)) = 512 . It will have such effect that dom0 kernel … Read more
Intentionally cause an I/O error in Linux?
Yes, theres a very plausible way to do this with device mapper. The device mapper can recombine block devices into a new mapping/order of your choosing. LVM does this. It also supports other targets, (some which are quite novel) like ‘flakey’ to simiulate a failing disk and ‘error’ to simulate failed regions of disk. One … Read more