From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f169.google.com ([209.85.223.169]:35890 "EHLO mail-io0-f169.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750922AbdHaLqA (ORCPT ); Thu, 31 Aug 2017 07:46:00 -0400 Received: by mail-io0-f169.google.com with SMTP id f99so13139525ioi.3 for ; Thu, 31 Aug 2017 04:45:59 -0700 (PDT) Subject: Re: mount time for big filesystems To: Roman Mamedov , Marco Lorenzo Crociani Cc: linux-btrfs@vger.kernel.org References: <556e7650-8556-d5ca-273e-6c158c1d032e@prismatelecomtesting.com> <20170831163656.6be88191@natsu> From: "Austin S. Hemmelgarn" Message-ID: Date: Thu, 31 Aug 2017 07:45:55 -0400 MIME-Version: 1.0 In-Reply-To: <20170831163656.6be88191@natsu> Content-Type: text/plain; charset=utf-8; format=flowed Sender: linux-btrfs-owner@vger.kernel.org List-ID: On 2017-08-31 07:36, Roman Mamedov wrote: > On Thu, 31 Aug 2017 12:43:19 +0200 > 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? > > 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. If you use dm-cache (what LVM uses), you need to be _VERY_ careful and can't use it safely at all with multi-device volumes because it leaves the underlying block device exposed. > > As for in general, with your FS size perhaps you should be using > "space_cache=v2" for better performance, but I'm not sure if that will have > any effect on mount time (aside from slowing down the first mount with that). It shouldn't have any other impact on mount time, but it may speed up other operations.