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Thread: Final Result: 2 SSD's on a laptop + BtrFS pseudo-raid BOOT

  1. #1

    Default Final Result: 2 SSD's on a laptop + BtrFS pseudo-raid BOOT

    Hi All: I had been experimenting with using two SSD's (two Samsung 870's; 2TB) on a HP ZBooK 15 i7-4700MQ laptop using BtrFS.

    I was primarily after two things - redundancy (self-healing of all disc errors - which apparently requires a type of btrfs-raid) and a flat file system between the two drives. The flat file system is to avoid issues with partition sizing and having to move files around... (this interferes with regular data backups b/c of user-confusion). Apparently the btrfs-raid is still a no-go on these SSD's, and I specifically wanted to use these SSD's b/c of reputation for reliability. So the only thing I could do was attempt a flat file system between the two drives during install...

    I had a lot of trouble during several installs, until I found the secret, which exists (at least) in 15.3: During install onto bare metal, choose Guided Partitioning (I think that's the right title). I had always manually partitioned my drives, but I was unable to come out with an easily-booted system doing this with BtrFS spanning 2 drives. With Guided Partitioning, you can instruct the installer to use all drives, and it will, apparently by default, form a single large BtrFS partition spanning the drives.

    There's also another advantage - you can edit fstab afterwards to add --compression=lzo to your root partition in order to get more HD space! I have found it doesn't slow things down perceptively - possibly due to the use of SSD's, (which are very fast).

    Easypeasy! And how it's the closest to an easily-booted system that I have achieved so far. You must (apparently) choose UEFI ONLY as a BIOS option on your laptop before installing - or else you'll wind up with an install in which you have to boot several times while trying to find the right EFI file from which to boot, using UEFI hotkeys. (I was unable to get any boot at all, post-install, when I chose "BIOS legacy" boot.) But even with UEFI - it will report "no operating system found" so you have to activate the UEFI Boot Manager by using the correct UEFI hotkey at power-on... Then you get the options to boot from drives, a EFI file, or "opensuse." Thus, it only takes minimal user-intervention to actually get the system to boot - but the process is reliable.

    So boot still isn't totally automatic - but it's reliable. Backups are super easy-because you just backup any desired parts of the filesystem (using rsync) to a big USB external drive. If you format that external drive with BtrFS, you can mount it (in fstab) with --compression=lzo to make even more space. You can also do snapshots of the laptop drive (I haven't tried this yet) and partition the external backup drive for data+metadata redundancy (which cuts the size of the hard drive in half, although some space is recovered with --compression=lzo).

    It appears BtrFS still isn't fully-integrated into BIOS/UEFI. I'd be interested if spinning HD's could be used in RAID0 (striping) to get much faster access times - if so, it might be worth replacing SSD's with (larger) spinning drives in order to obtain at least metadata redundancy (for FS-level automatic error-correction). Also, it would be useful to know if hybrid SSHDs are fully integrated into BtrFS raid setups (for increased speed over spinning HDs). A pair of 4TB spinning drives would give the same size as my current SSD system if set for full data + metadata redundancy and autocorrection - and may be fast when using raid0. But so far it's unclear whether btrfs-raid0 offers the speed advantage of traditional raid0. https://en.wikipedia.org/wiki/Standard_RAID_levels

  2. #2

    Default Re: Final Result: 2 SSD's on a laptop + BtrFS pseudo-raid BOOT

    HDDs are too slow for Btrfs. RAID will not help with that.
    Check https://en.wikipedia.org/wiki/ZFS

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