Re: [GTALUG] Question Fodder: Bcache Filesystem

[Dave Collier-Brown via talk]

I was using bcache at one point at World Gaming, with a borrowed flash card, 
but luckily stopped doing so just before a (possibly different) corruption 
problem.

--dave

On 2019-05-14 5:12 p.m., Christopher Browne via talk wrote:
I just saw a report of corruption problems with bcache in conjunction with GCC 
9, and realized I had never actually heard of bcache before.

https://en.wikipedia.org/wiki/Bcache
- a layer in the kernel for using fast storage (e.g. - NAND, SSD) as a cache 
for spinning rust

That's pretty cool; I don't have enough lurking SSD/NAND to have that be of 
*too* much interest.  But wait, they kept working on it, so there's a 
filesystem...

https://en.wikipedia.org/wiki/Bcachefs
- a COW (Copy On Write) filesystem running atop BCache that has the modern 
stuff people seem to like such as snapshotting, encryption, checksums, 
compression (ala ZFS, Btrfs)

Here's the corruption reference: 
https://bugzilla.kernel.org/show_bug.cgi?id=203573
And some more diagnosis here: 
https://bugzilla.redhat.com/show_bug.cgi?id=1708315

Sounds like it may be the wrong moment in time to be adopting BCache-related 
stuff ;-)

Has anyone been poking at this sort of stuff?  A *lng* time ago, I used to 
follow ReiserFS pretty closely, back when that project was a technical matter, 
as opposed to being (rather properly!) overshadowed by a murder investigation 
:-(
--
When confronted by a difficult problem, solve it by reducing it to the
question, "How would the Lone Ranger handle this?"



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David Collier-Brown, | Always do right. This will gratify
System Programmer and Author | some people and astonish the rest
dave.collier-br...@indexexchange.com
 |  -- Mark Twain



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Re: [GTALUG] Question Fodder: Bcache Filesystem

[Jamon Camisso via talk]

On 5/14/19 5:12 PM, Christopher Browne via talk wrote:

Sounds like it may be the wrong moment in time to be adopting
BCache-related stuff ;-)

Has anyone been poking at this sort of stuff?  A *lng* time ago, I used
to follow ReiserFS pretty closely, back when that project was a technical
matter, as opposed to being (rather properly!) overshadowed by a murder
investigation :-(


We use it for every customer's Openstack cloud for almost every 
openstack component. Nova, Ceph, Swift, Keystone, and MySQL are the 
major services, and each has a bcache underlay along with a hardware 
RAID controller.


It has proven to be quite a reliable (and fast) setup, and even in the 
event of a power cut we haven't lost any data.


For nova especially where users are interacting with VMs, it means a 
customer can have large amounts of storage allocated for a VM, and 
writes feel as though the whole system is running on an SSD.


Likewise for Keystone & MySQL, where in busy clouds with clustered 
MySQL, tokens can take a long time to generate, fetch, and authenticate 
without the SSD backing.


All around quite useful, just don't run it on the leading edge of GCC, 
Kernel, and OS releases!

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[GTALUG] Question Fodder: Bcache Filesystem

[Christopher Browne via talk]

I just saw a report of corruption problems with bcache in conjunction with
GCC 9, and realized I had never actually heard of bcache before.

https://en.wikipedia.org/wiki/Bcache
- a layer in the kernel for using fast storage (e.g. - NAND, SSD) as a
cache for spinning rust

That's pretty cool; I don't have enough lurking SSD/NAND to have that be of
*too* much interest.  But wait, they kept working on it, so there's a
filesystem...

https://en.wikipedia.org/wiki/Bcachefs
- a COW (Copy On Write) filesystem running atop BCache that has the modern
stuff people seem to like such as snapshotting, encryption, checksums,
compression (ala ZFS, Btrfs)

Here's the corruption reference:
https://bugzilla.kernel.org/show_bug.cgi?id=203573
And some more diagnosis here:
https://bugzilla.redhat.com/show_bug.cgi?id=1708315

Sounds like it may be the wrong moment in time to be adopting
BCache-related stuff ;-)

Has anyone been poking at this sort of stuff?  A *lng* time ago, I used
to follow ReiserFS pretty closely, back when that project was a technical
matter, as opposed to being (rather properly!) overshadowed by a murder
investigation :-(
-- 
When confronted by a difficult problem, solve it by reducing it to the
question, "How would the Lone Ranger handle this?"
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