I have selection of hard drives, with capacities:
1 TB 500 GB 320 GB 250 GB
I'd like to make Raid1 out of them, in the sense, that copy of any data will be always on two drives out of four I have. Problem is, that all drives have different capacities. In the past I've been running normal Raid1 mdadm 2x 2TB, Btrfs with 2x 2TB after I migrated from mdadm. I don't mind to use mdadm again, or Btrfs, or ZFS, although I know nothing about that one.
What would be best filesystem or utility for me, which fits this criteria:
- to have two copies of files at all times, so if one disk dies, I don't lose data
- have at much at possible available space with still meet criteria from point 1
What should I use? I have feeling Btrfs Raid1 will handle this, and story exactly two copies of every file across all four hard drives, but I am not sure. I have Linux on AMD64 computer, with 5.10 kernel.
Any advice welcome.
EDIT - SOLUTION!
Thanks very much for all your replies! So I went ahead with Btrfs Raid1 configuration, It was time consuming process, but very painless, because I'm already familiar Btrfs and use it daily. I figured that wouldn't lose any physical space with Raid1, while maintaining redundancy ratio of 2. I used this calculator: https://carfax.org.uk/btrfs-usage/
My device sizes:
931.51 GiB 465.76 GiB 298.09 GiB 232.89 GiB Total space for files in Raid1 mode: 963 GiB (all space used) Total space for files in Raid5 mode: 995 GiB (466 GiB unusable on biggest drive)
With Raid1, I have now 719.5 GiB data stored and 241.6 GiB free, for total of 961.1 GiB, which matches what calculator said. And I can add/remove drives later at will. Amazing.
I'm tempted to go for Raid5, because it gives theoretical read speed gain of 4x, while Raid1 gives 2x. But I heard it's a bit experimental at the moment and not recommended for daily use, it that correct? What's its state on 5.10 kernel, anyone uses it and can share their experience?
Following building the array, adding all drives one by one and migrating all data to it (I have backups), I did full scrub and everything is fine:
$ sudo btrfs scrub start -Bd /home Scrub device /dev/sda (id 1) done Scrub started: Thu Jun 17 10:10:38 2021 Status: finished Duration: 2:38:51 Total to scrub: 724.03GiB Rate: 77.53MiB/s Error summary: no errors found Scrub device /dev/sdd (id 2) done Scrub started: Thu Jun 17 10:10:38 2021 Status: finished Duration: 1:52:39 Total to scrub: 374.03GiB Rate: 56.57MiB/s Error summary: no errors found Scrub device /dev/sdc (id 3) done Scrub started: Thu Jun 17 10:10:38 2021 Status: finished Duration: 0:48:06 Total to scrub: 207.00GiB Rate: 73.09MiB/s Error summary: no errors found Scrub device /dev/sdb (id 4) done Scrub started: Thu Jun 17 10:10:38 2021 Status: finished Duration: 0:30:00 Total to scrub: 143.00GiB Rate: 80.89MiB/s Error summary: no errors found
EDIT - COMMENTS FOR @Marcus Müller:
"Remarks: are you sure you want this? 320 GB and 250 GB are probably not very new drives (...)"
You are very correct, these are very old drives! I removed my current 2x 2TB Seagate Barracuda Compute drives which I had on Btrfs Raid1 for last few years, to put these random 4x old aged drives. Barracudas are going to my server, which needs total reliability, I have 2x SSD 250GB for / there (Ext4 mdadm), and 2x HDD TB for /home and /var (Btrfs Raid1), and with ECC RAM. Another two Barracudas will join first two, for Btrfs Raid1 mode or possibly Raid10 or Raid5.
4x Old drives are now sitting in my desktop, they consist of:
Western Digital Blue Mobile, WDC WD10JPVX-60JC3T0 [1.00 TB, 4K sectors, SATA 3.0, 6.0 Gb/s, 5400 RPM, 2.5"] Power_On_Hours 2496 Reallocated_Sector_Ct 0 Toshiba 2.5" HDD MK..65GSX, TOSHIBA MK5065GSX [500 GB, 512 sectors, SATA 2.6, 3.0 Gb/s, 5400 RPM, 2.5"] Power_On_Hours 2519 Reallocated_Sector_Ct 293 Seagate Momentus Thin, ST320LT007-9ZV142 [320 GB, 4K sectors, SATA 2.6, 3.0 Gb/s, 7200 RPM, 2.5"] Power_On_Hours 5152 Reallocated_Sector_Ct 0 Seagate Barracuda 7200.12,ST3250318AS [250 GB, 512 sectors, SATA 2.6, 3.0 Gb/s, 7200 RPM, 3.5"] Power_On_Hours 6591 Reallocated_Sector_Ct 3251
That's a monster cocktail, I have to admit :D haha. Reliability is not an issue really, I have backups, but I don't want any painful surprises too quickly, so basic redundancy of 2.0 will save my trouble if one of the drives die within a year or so, I will just slap in another one or two.
Disclaimer: I Spinrite'd all drives (I do that on regular basis on all my drives), zero'd them, benchmark them, fully scrubbed Btrfs filesystem (I also do that on regular basis), they have no further bad sectors at the moment. And if they develop more over time, that would be perfect test for Spinrite to fix them, or at least for me to learn what Btrfs will do in this scenario!