The Four Different Schemes for Persistent Naming LVM logical volumes should always be identified by logical volume name ( /dev/mapper/ name). That's why Debian encourages you to change your setup to persistent naming schemes, unless you are using LVM. There are more reasons, but these are the most critical ones now and in the near future. (The postinst for the package linux-base includes code to assist with the changeover, but it makes sense to get it sorted out and verified as working in advance.)īig machines, with many fast CPUs, and many Fiber Channel Host Bus Adapters, variable load/latency FC switches, SCSI controllers, and/or high-performance network cards, may have asynchronous timing issues when dealing with udev and multipath I/O, with almost unpredictable device detection order and automatic assignment of names during boot. Again, if you have persistent naming in place, you won't even notice. Persistent naming allows you not to worry about this at all.įor machines with IDE controllers (including for instance machines with all-SATA hard drives and just one IDE cdrom drive), the switch to a standard Squeeze kernel may cause trouble: with the introduction of the new libata PATA support, your IDE hdX devices will become sdX devices. The result is that device names like /dev/sda1 and /dev/sdb1 may switch around randomly on each boot.
If you have more than one disk controller (IDE or especially SCSI/SATA), or even if you just have variable numbers of removable USB/firewire storage devices attached from day to day, the order in which they are detected may not be deterministic. While Linux distributions and udev are evolving and hardware detection is becoming more reliable, there are also a number of new problems and changes: Persistent device naming for block devices has been made possible by the introduction of udev and has some advantages over the use of traditional bus-based names such as /dev/hda1 or /dev/sda2. Assigning Persistent Names to Swap Partitions.The Four Different Schemes for Persistent Naming.
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