On 2017-08-31 07:00, Hans van Kranenburg wrote:
On 08/31/2017 12:43 PM, Marco Lorenzo Crociani wrote:
Hi,
this 37T filesystem took some times to mount. It has 47
subvolumes/snapshots and is mounted with
noatime,compress=zlib,space_cache. Is it normal, due to its size?
Yes, unfortunately it is. It depends on the size of the metadata extent
tree. During mount, the BLOCK_GROUP_ITEM objects are loaded from that
tree. They're scattered all around, causing a lot of random reads when
your disk cache is still ice cold.
FWIW, you can (sometimes) improve things by running a full balance.
Other than that, there's not much that can be done unless BTRFS gets
changed to actively group certain data close to each other on disk
(which would be nice for other reasons too TBH).
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