[Nottingham] I knew I'd forget something last night (filesystems and partitions)

Fri May 22 14:54:03 UTC 2020

Hello,

On Fri, May 22, 2020 at 02:03:54AM +0100, Martin via Nottingham wrote:
> Good luck!

Apart from having to remount (I chose actually to reboot) it's going
okay so far…

May 22 12:20:57 specialbrew kernel: [22232153.857928] ata6.06: SATA link up 3.0 Gbps (SStatus 123 SControl 320)
May 22 12:20:57 specialbrew kernel: [22232153.863058] ata6.06: supports DRM functions and may not be fully accessible
May 22 12:20:57 specialbrew kernel: [22232153.867485] ata6.06: ATA-11: Samsung SSD 860 QVO 2TB, RVQ01B6Q, max UDMA/133
May 22 12:20:57 specialbrew kernel: [22232153.871817] ata6.06: 3907029168 sectors, multi 1: LBA48 NCQ (depth 31/32)
May 22 12:20:57 specialbrew kernel: [22232153.878755] ata6.06: supports DRM functions and may not be fully accessible
May 22 12:20:57 specialbrew kernel: [22232153.884930] ata6.06: configured for UDMA/100
May 22 12:20:57 specialbrew kernel: [22232153.889813] scsi 5:6:0:0: Direct-Access     ATA      Samsung SSD 860  1B6Q PQ: 0 ANSI: 5
May 22 12:20:57 specialbrew kernel: [22232153.895321] ata6.06: Enabling discard_zeroes_data
May 22 12:20:57 specialbrew kernel: [22232153.895338] sd 5:6:0:0: Attached scsi generic sg8 type 0
May 22 12:20:57 specialbrew kernel: [22232153.900519] sd 5:6:0:0: [sdk] 3907029168 512-byte logical blocks: (2.00 TB/1.82 TiB)
May 22 12:20:57 specialbrew kernel: [22232153.909348] sd 5:6:0:0: [sdk] Write Protect is off
May 22 12:20:57 specialbrew kernel: [22232153.913903] sd 5:6:0:0: [sdk] Mode Sense: 00 3a 00 00
May 22 12:20:57 specialbrew kernel: [22232153.913936] sd 5:6:0:0: [sdk] Write cache: enabled, read cache: enabled, doesn't support DPO or FUA
May 22 12:20:57 specialbrew kernel: [22232153.919917] ata6.06: Enabling discard_zeroes_data
May 22 12:20:57 specialbrew kernel: [22232153.926299] ata6.06: Enabling discard_zeroes_data
May 22 12:20:57 specialbrew kernel: [22232153.933660] sd 5:6:0:0: [sdk] supports TCG Opal
May 22 12:20:57 specialbrew kernel: [22232153.938526] sd 5:6:0:0: [sdk] Attached SCSI disk

(After reboot this became sdf; the faulty device appeared again as sdj)

$ sudo btrfs replace start -B -r /dev/sdj /dev/disk/by-id/ata-Samsung_SSD_860_QVO_2TB_serialnohere /srv/tank

$ sudo sh -c 'while true; do btrfs replace status -1 /srv/tank; sleep 600; done' | ts
May 22 12:55:48 2.5% done, 0 write errs, 0 uncorr. read errs
May 22 13:05:48 3.8% done, 0 write errs, 0 uncorr. read errs
May 22 13:15:48 5.7% done, 0 write errs, 0 uncorr. read errs
May 22 13:25:48 7.6% done, 0 write errs, 0 uncorr. read errs
May 22 13:35:48 9.6% done, 0 write errs, 0 uncorr. read errs
May 22 13:45:48 11.5% done, 0 write errs, 0 uncorr. read errs
May 22 13:55:48 13.5% done, 0 write errs, 0 uncorr. read errs
May 22 14:05:48 15.4% done, 0 write errs, 0 uncorr. read errs
May 22 14:15:48 17.3% done, 0 write errs, 0 uncorr. read errs
May 22 14:25:48 19.3% done, 0 write errs, 0 uncorr. read errs
May 22 14:35:48 21.2% done, 0 write errs, 0 uncorr. read errs
May 22 14:45:48 23.1% done, 0 write errs, 0 uncorr. read errs

If I keep it mounted degraded all the time, does that mean I can
remove/replace devices at will?

Other storage innovations going on:

Red Hat's Stratis: https://stratis-storage.github.io/StratisSoftwareDesign.pdf

This uses XFS and device mapper underneath but a userland daemon to
manage it all so you only interact with that. Will support
encryption, integrity (checksums), cache tier, snapshots, device
add/remove, and typical volume management. Though much of that is
"in a later version".

mdraid on LUKS on dm-integrity:
https://gist.github.com/MawKKe/caa2bbf7edcc072129d73b61ae7815fb

Integrity and encryption.

Or use LVM on top of (or instead of) md to get full volume management, snapshots etc.

You could add a cache tier with dm-cache.

All of this is basically what Stratis is doing, but you do it by
hand using the lower level tools.

I'd be really interested to see benchmarks of this versus just
LVM-on-MD, with and without LUKS, and against ZFS.

Cheers,
Andy

-- 
https://bitfolk.com/ -- No-nonsense VPS hosting