From: " " <Cedric.dewijs@eclipso.eu>
To: "Andy Smith" <andy@strugglers.net>
Cc: <linux-btrfs@vger.kernel.org>, <linux-raid@vger.kernel.org>
Subject: Re: Re: put 2 hard drives in mdadm raid 1 and detect bitrot like btrfs does, what's that called?
Date: Thu, 04 Feb 2021 18:43:23 +0100 [thread overview]
Message-ID: <24e578627d205151df16b5aebe4a551e@mail.eclipso.de> (raw)
In-Reply-To: <20210204105457.GI3712@bitfolk.com>
--- Ursprüngliche Nachricht ---
Von: Andy Smith <andy@strugglers.net>
Datum: 04.02.2021 11:54:57
An: linux-btrfs@vger.kernel.org
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@vger.kernel.org/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
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next prev parent reply other threads:[~2021-02-04 17:44 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <f5d8af48e8d5543267089286c01c476f@mail.eclipso.de>
[not found] ` <a2cd87208a74fb36224539fa10727066@mail.eclipso.de>
2021-02-04 10:54 ` put 2 hard drives in mdadm raid 1 and detect bitrot like btrfs does, what's that called? Andy Smith
2021-02-04 17:43 ` [this message]
2021-02-04 18:13 ` Goffredo Baroncelli
2021-02-04 19:58 `
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