--- Ursprüngliche Nachricht --- Von: Andy Smith <andy@xxxxxxxxxxxxxx> Datum: 04.02.2021 11:54:57 An: linux-btrfs@xxxxxxxxxxxxxxx Betreff: Re: put 2 hard drives in mdadm raid 1 and detect bitrot like btrfs does, what's that called? Hi Cedric, On Wed, Feb 03, 2021 at 08:33:18PM +0100, wrote: > it's called "dm-integrity", as mentioned in this e-mail: > https://www.mail-archive.com/linux-btrfs@xxxxxxxxxxxxxxx/msg93037.html If you do this it would be very interesting to see performance figures for the following setups: - btrfs with raid1 meta and data allocation - mdadm raid1 on raw devices - mdadm raid1 on dm-integrity (no encryption) on raw devices - mdadm raid1 on dm-integrity (encryption) on raw devices just to see what kind of performance loss dm-integrity and encryption is going to impose. After doing it, it would find a nice home on the Linux RAID wiki: https://raid.wiki.kernel.org/index.php/Dm-integrity Cheers, Andy Hey Andy, I would rather see performance figures for these setups: A) btrfs with 2 (or more) hard drives and one SSD in writeback bcache configuration (unsafe against failure of the ssd): +-----------------------------+ | btrfs raid 1 /mnt | +--------------+--------------+ | /dev/Bcache0 | /dev/Bcache1 | +--------------+--------------+ | bcache writeback Cache | | /dev/sdk1 | +--------------+--------------+ | Data | Data | | /dev/sdv1 | /dev/sdw1 | +--------------+--------------+ B) btrfs with 2 (or more) hard drives and two SSD's in dm-raid 1 writeback bcache configuration (unsafe against corruption of any of the ssd's): +-----------------------------+ | btrfs raid 1 /mnt | +--------------+--------------+ | /dev/Bcache0 | /dev/Bcache1 | +--------------+--------------+ | bcache writeback Cache | | /dev/dm0 | +--------------+--------------+ | 2x SSD in mdadm raid 1 | | /dev/sdk1 /dev/sdl1 | +--------------+--------------+ | Data | Data | | /dev/sdv1 | /dev/sdw1 | +--------------+--------------+ C) Full stack: btrfs with 2 (or more) hard drives and two identical SSD's in dm-raid 1 with dm-integrity writeback bcache configuration (safe against any failed drive): +-----------------------------+ | btrfs raid 1 /mnt | +--------------+--------------+ | /dev/Bcache0 | /dev/Bcache1 | +--------------+--------------+ | bcache writeback Cache | | /dev/dm0 | +--------------+--------------+ | 2 x dm-integrity devices | | in mdadm raid 1 | +--------------+--------------+ | SSD hosting | SSD hosting | | dm-integrity | dm-integrity | | /dev/sdk1 | /dev/sdl1 | +--------------+--------------+ | Data | Data | | /dev/sdv1 | /dev/sdw1 | +--------------+--------------+ D) Full stack: btrfs with 2 (or more) hard drives and two SSD's (one slow, and one very fast) in dm-raid 1 with dm-integrity writeback bcache configuration (safe against any failed drive): +-----------------------------+ | btrfs raid 1 /mnt | +--------------+--------------+ | /dev/Bcache0 | /dev/Bcache1 | +--------------+--------------+ | bcache writeback Cache | | /dev/dm0 | +--------------+--------------+ | 2 x dm-integrity devices | | in mdadm raid 1 | +--------------+--------------+ | SSD hosting | SSD hosting | | dm-integrity | dm-integrity | | /dev/sdk1 | /dev/sdl1 | +--------------+--------------+ | Data | Data | | /dev/sdv1 | /dev/sdw1 | +--------------+--------------+ In all these setups, the performance of the hard drives is irrelevant, because the speed of the setups comes from the bcache SSD. Cheers, Cedric --- Take your mailboxes with you. Free, fast and secure Mail & Cloud: https://www.eclipso.eu - Time to change!
