From: "Austin S. Hemmelgarn" <ahferroin7@gmail.com>
To: Hans van Kranenburg <hans.van.kranenburg@mendix.com>,
Marco Lorenzo Crociani <marcoc@prismatelecomtesting.com>,
linux-btrfs@vger.kernel.org
Subject: Re: mount time for big filesystems
Date: Thu, 31 Aug 2017 07:22:18 -0400 [thread overview]
Message-ID: <c2d51a94-048f-13cd-401a-f531450ceccf@gmail.com> (raw)
In-Reply-To: <7fbe45ea-9991-8e81-831f-10c9526b2a01@mendix.com>
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).
next prev parent reply other threads:[~2017-08-31 11:22 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-31 10:43 mount time for big filesystems Marco Lorenzo Crociani
2017-08-31 11:00 ` Hans van Kranenburg
2017-08-31 11:22 ` Austin S. Hemmelgarn [this message]
2017-08-31 11:36 ` Roman Mamedov
2017-08-31 11:45 ` Austin S. Hemmelgarn
2017-08-31 12:16 ` Roman Mamedov
2017-08-31 14:13 ` Qu Wenruo
2017-09-01 13:52 ` Juan Orti Alcaine
2017-09-01 13:59 ` Austin S. Hemmelgarn
[not found] ` <CAC+fKQWFbdF6b3jGO_6hG_pNNzKobBYMeSNyEi5XRCf5YKa81Q@mail.gmail.com>
2017-09-01 15:20 ` Austin S. Hemmelgarn
2017-09-01 22:41 ` Dan Merillat
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