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I have a ~8TB NAS on an Atom C2758 system. I've loaded less than 4TB so far and FreeNAS is really getting on my nerves. Am I "protected" from a single drive fai

I have a ~8TB NAS on an Atom C2758 system. I've loaded less than 4TB so far and FreeNAS is really getting on my nerves. Am I "protected" from a single drive failure with LVM? Can I grow the storage size by swapping out one drive at a time? If so, I might just go to Debian and be done with it, although FreeBSD 10's bhyve hypervisor looks really good.

unethical_ban 11y ago
What's the problem?
- voltagex_ 11y ago
  The FreeBSD 9 base makes it really hard to mount ext4 drives (no FUSE until 10), the security patching regime relies on upgrading the whole rootfs (see the SSH client vuln today) and I'm in unfamiliar territory on a BSD having used Linux for the last decade.
  - benjaminl 11y ago
    I am running ZFS on Linux and it is working great for me. ZFS on Linux is considered production ready[0]. A lot of the showstoppers, like being able to boot from ZFS have been worked out. [0] - https://clusterhq.com/2014/09/11/state-zfs-on-linux/ https://clusterhq.com/2014/09/11/state-zfs-on-linux/
    - XorNot 11y ago
      Here here for ZFS on Linux as well. My home server is built in one of these http://www.u-nas.com/product/nsc800.html http://www.u-nas.com/product/nsc800.html with a C2550D4I motherboard and 8 4TB drives in RAIDZ2. Runs great, and I've got the drives configured for spin-down when not in use to conserve power. It's the successor to the 20-disk system I setup while I was still at my parents house, though that's a lot noisier (but fortunately lives in the basement service room) - downside is it's all based on 1.5 and 2TB disks, upside is RAIDZ3 is really nice to have.
benjaminl 11y ago
No, LVM doesn't provide any protection, you need to layer mdadm below LVM to provide any sort of protection. Even with the use of mdadm, it doesn't provide near the sort of protection that ZFS does. Due to pervasive checksuming of data, ZFS handles the bit-rot and corruption that a dying disk does much better than the traditional raid that mdadm provides. For example if you have your disks mirrored or RAIDed, if the disk doesn't provide a read error, mdadm will pass the data back to the OS. Since the data isn't checksumed, there is no way for it to know if it needs to read from the mirrored disk or the parity drives.
- voltagex_ 11y ago
  Thanks. I'm hanging out for FreeNAS 10, which seems like it will solve a lot of things.
- bryanlarsen 11y ago
  - as of RHEL 6.3, LVM supports raid4/5/6 without mdadm. It has supported raid1 (mirroring) and raid0 (striping) for much longer. - any LVM or mdadm mode with parity contains a functional checksum. To use it for data integrity, do a regular scrub. You should be doing a regular scrub with ZFS anyways, so ZFS's checksum on read doesn't add much except for slowing things down.
  - Ded7xSEoPKYNsDd 11y ago
    > any LVM or mdadm mode with parity contains a functional checksum. To use it for data integrity, do a regular scrub. That doesn't work. Scrubbing the RAID can detect errors, but when they occur, the block layer has no idea which copy is the correct one. I haven't verified for LVM, but at least for mdraid, Linux explicitly does not make any attempts at recovering a 'correct' block even in cases where there is more than one copy. It just randomly picks a winner and overwrites the other versions. You still want to scrub for the error detection.
    - bryanlarsen 11y ago
      I've seen it work. It knows which block has the error because the disk reported the error. It then rewrites the sector with the correct data, the disk moves the sector, you see "read error detected, corrected" or some such in your kernel logs.

unethical_ban 11y ago

What's the problem?

voltagex_ 11y ago
The FreeBSD 9 base makes it really hard to mount ext4 drives (no FUSE until 10), the security patching regime relies on upgrading the whole rootfs (see the SSH client vuln today) and I'm in unfamiliar territory on a BSD having used Linux for the last decade.
- benjaminl 11y ago
  I am running ZFS on Linux and it is working great for me. ZFS on Linux is considered production ready[0]. A lot of the showstoppers, like being able to boot from ZFS have been worked out. [0] - https://clusterhq.com/2014/09/11/state-zfs-on-linux/ https://clusterhq.com/2014/09/11/state-zfs-on-linux/
  - XorNot 11y ago
    Here here for ZFS on Linux as well. My home server is built in one of these http://www.u-nas.com/product/nsc800.html http://www.u-nas.com/product/nsc800.html with a C2550D4I motherboard and 8 4TB drives in RAIDZ2. Runs great, and I've got the drives configured for spin-down when not in use to conserve power. It's the successor to the 20-disk system I setup while I was still at my parents house, though that's a lot noisier (but fortunately lives in the basement service room) - downside is it's all based on 1.5 and 2TB disks, upside is RAIDZ3 is really nice to have.

benjaminl 11y ago

No, LVM doesn't provide any protection, you need to layer mdadm below LVM to provide any sort of protection. Even with the use of mdadm, it doesn't provide near the sort of protection that ZFS does. Due to pervasive checksuming of data, ZFS handles the bit-rot and corruption that a dying disk does much better than the traditional raid that mdadm provides. For example if you have your disks mirrored or RAIDed, if the disk doesn't provide a read error, mdadm will pass the data back to the OS. Since the data isn't checksumed, there is no way for it to know if it needs to read from the mirrored disk or the parity drives.

voltagex_ 11y ago
Thanks. I'm hanging out for FreeNAS 10, which seems like it will solve a lot of things.
bryanlarsen 11y ago
- as of RHEL 6.3, LVM supports raid4/5/6 without mdadm. It has supported raid1 (mirroring) and raid0 (striping) for much longer. - any LVM or mdadm mode with parity contains a functional checksum. To use it for data integrity, do a regular scrub. You should be doing a regular scrub with ZFS anyways, so ZFS's checksum on read doesn't add much except for slowing things down.
- Ded7xSEoPKYNsDd 11y ago
  > any LVM or mdadm mode with parity contains a functional checksum. To use it for data integrity, do a regular scrub. That doesn't work. Scrubbing the RAID can detect errors, but when they occur, the block layer has no idea which copy is the correct one. I haven't verified for LVM, but at least for mdraid, Linux explicitly does not make any attempts at recovering a 'correct' block even in cases where there is more than one copy. It just randomly picks a winner and overwrites the other versions. You still want to scrub for the error detection.
  - bryanlarsen 11y ago
    I've seen it work. It knows which block has the error because the disk reported the error. It then rewrites the sector with the correct data, the disk moves the sector, you see "read error detected, corrected" or some such in your kernel logs.