On 2017-09-01 09:52, Juan Orti Alcaine wrote:
2017-08-31 13:36 GMT+02:00 Roman Mamedov <r...@romanrm.net>:
If you could implement SSD caching in front of your FS (such as lvmcache or
bcache), that would work wonders for performance in general, and especially
for mount times. I have seen amazing results with lvmcache (of just 32 GB) for
a 14 TB FS.
I'm thinking about adding a SSD for my 4 disks RAID1 filesystem, but I
have doubts about how to correctly do it in a multidevice filesystem.
I guess I should make 4 partitions on the SSD and pair them with my
backing devices, then create the btrfs on top of bcache0, bcache1,...
is this the right way to do it?
If you are going to use bcache, you don't need separate caches for each
device (and in fact, you're probably better off sharing a cache across
devices).
If instead you're going to use dm-cache/LVM, you will need two logical
volumes per-device for the cache, one big one (for the actual cache),
and one little one (for metadata, usually a few hundred MB is fine).
In general though, you're correct, it is preferred to do things in the
order you suggested. It is technically possible sometimes to convert an
existing device to being cached in-place, but it's risky, and restoring
from a backup onto a clean filesystem has other benefits too.
--
To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in
the body of a message to majord...@vger.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
