Re: [PATCH RFC 0/2] dm-zoned: add cache device

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On 3/23/20 4:15 PM, Mike Snitzer wrote:
On Mon, Mar 23 2020 at 11:03am -0400,
Hannes Reinecke <hare@xxxxxxx> wrote:

Hi Damien,

as my original plan to upgrade bcache to work for SMR devices
turned out to be more complex than anticipated I went for the
simpler approach and added a 'cache' device for dm-zoned.
It is using a normal device (eg '/dev/pmem0' :-), split it
into zones of the same size of the original SMR device, and
makes those 'virtual' zones avialable to dm-zoned in a similar
manner than the existing 'random write' zoned.

The implementation is still a bit rough (one would need to add
metadata to the cache device, too), but so far it seems to work
quite well; still running after copying 300GB of data back and forth.

As usual, comments and reviews are welcome.

Not seeing why this needs to be so specialized (natively implemented in
dm-zoned).  Did you try stacking dm-writecache on dm-zoned?

dm-zoned is using the random-write zones internally to stage writes to the sequential zones, so in effect it already has an internal caching.
All this patch does is to use a different device for the already present
mechanism.
Using dm-writecache would be ignorant of that mechanism, leading to double caching and detrimental results.

Cheers,

Hannes
--
Dr. Hannes Reinecke            Teamlead Storage & Networking
hare@xxxxxxx                               +49 911 74053 688
SUSE Software Solutions GmbH, Maxfeldstr. 5, 90409 Nürnberg
HRB 36809 (AG Nürnberg), Geschäftsführer: Felix Imendörffer


--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel




[Index of Archives]     [DM Crypt]     [Fedora Desktop]     [ATA RAID]     [Fedora Marketing]     [Fedora Packaging]     [Fedora SELinux]     [Yosemite Discussion]     [KDE Users]     [Fedora Docs]

  Powered by Linux