On Tue, Jun 7, 2011 at 5:22 AM, River Tarnell <river.tarn...@wikimedia.de> wrote: > ZFS snapshots are nice, but OTOH ZFS can't remove storage from a pool or > do any kind of online relayout, both of which are standard features in > VxVM (and I assume in Linux LVM as well, although I have no experience > of it.)
Linux LVM can do anything you want online, in my experience: grow and shrink logical volumes, move logical volumes between physical volumes within the same volume group, and add or remove physical volumes, for instance. I've found that moving physical volumes is much slower than it should be, though, and I've had bad experiences once or twice moving a PV that's being actively used (system hang, but no data loss and the operation continued automatically after power-cycling and completed successfully). md isn't quite so good about what it can do online, but it's getting better recently. It can add or remove devices from RAID1/5/6 online, and even change the RAID level online sometimes. If it doesn't do what you want, and you have enough storage attached, you can always create the new md device and move the old one's contents to it online using LVM, possibly leaving one or both RAID arrays degraded while you do so to get the extra space necessary. ext4 can grow online if you grow the device it's sitting on, but it can't shrink online, and (AFAIK) nor can any other high-profile Linux filesystem except btrfs. So in practice, on Linux you can do all your I/O-related stuff online except shrinking filesystems. This is usually enough, but the inability to shrink filesystems online can occasionally be a pain. btrfs is slated to fix this, in addition to solving world hunger and curing cancer. _______________________________________________ Toolserver-l mailing list (Toolserver-l@lists.wikimedia.org) https://lists.wikimedia.org/mailman/listinfo/toolserver-l Posting guidelines for this list: https://wiki.toolserver.org/view/Mailing_list_etiquette
