From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [IPv6:2a01:7e0:0:424::9]) by lore.proxmox.com (Postfix) with ESMTPS id 151AD1FF136 for ; Mon, 23 Mar 2026 10:58:42 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id F16B61041F; Mon, 23 Mar 2026 10:58:59 +0100 (CET) From: Maximiliano Sandoval To: Fiona Ebner Subject: Re: [pve-devel] [PATCH docs] storage: note that qcow2 internal snapshots are inefficient In-Reply-To: (Fiona Ebner's message of "Mon, 23 Mar 2026 10:47:39 +0100") References: <20251128155628.223336-1-f.ebner@proxmox.com> User-Agent: mu4e 1.12.9; emacs 30.1 Date: Mon, 23 Mar 2026 10:58:54 +0100 Message-ID: MIME-Version: 1.0 Content-Type: text/plain X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1774259889314 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.126 Adjusted score from AWL reputation of From: address BAYES_00 -1.9 Bayes spam probability is 0 to 1% DMARC_MISSING 0.1 Missing DMARC policy KAM_DMARC_STATUS 0.01 Test Rule for DKIM or SPF Failure with Strict Alignment RCVD_IN_VALIDITY_CERTIFIED_BLOCKED 0.001 ADMINISTRATOR NOTICE: The query to Validity was blocked. See https://knowledge.validity.com/hc/en-us/articles/20961730681243 for more information. RCVD_IN_VALIDITY_RPBL_BLOCKED 0.001 ADMINISTRATOR NOTICE: The query to Validity was blocked. See https://knowledge.validity.com/hc/en-us/articles/20961730681243 for more information. RCVD_IN_VALIDITY_SAFE_BLOCKED 0.001 ADMINISTRATOR NOTICE: The query to Validity was blocked. See https://knowledge.validity.com/hc/en-us/articles/20961730681243 for more information. SPF_HELO_NONE 0.001 SPF: HELO does not publish an SPF Record SPF_PASS -0.001 SPF: sender matches SPF record Message-ID-Hash: 5YSICFLIHTJZL5BM5RQ2STEWUVVCMFGC X-Message-ID-Hash: 5YSICFLIHTJZL5BM5RQ2STEWUVVCMFGC X-MailFrom: m.sandoval@proxmox.com X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; loop; banned-address; emergency; member-moderation; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header CC: pve-devel@lists.proxmox.com X-Mailman-Version: 3.3.10 Precedence: list List-Id: Proxmox VE development discussion List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: Fiona Ebner writes: > Am 28.11.25 um 4:56 PM schrieb Fiona Ebner: >> It's a commonly reported issue, most recently again in the enterprise >> support, that taking or removing snapshots of large qcow2 files on >> file-based network storages can take a very long time. Add a note >> about this limitation. >> >> Signed-off-by: Fiona Ebner >> --- >> pvesm.adoc | 5 +++++ >> 1 file changed, 5 insertions(+) >> >> diff --git a/pvesm.adoc b/pvesm.adoc >> index d36baf8..165b446 100644 >> --- a/pvesm.adoc >> +++ b/pvesm.adoc >> @@ -88,6 +88,11 @@ block device functionality. >> >> ^2^: On file based storages, snapshots are possible with the 'qcow2' format, >> either using the internal snapshot function, or snapshots as volume chains^4^. >> +Creating and deleting internal 'qcow2' snapshots will block a running VM and >> +is not an efficient operation. The performance is particularly bad with network >> +storages like NFS. On some setups and for large disks (multiple hundred GiB or >> +TiB sized), these operations may take several minutes, or in extreme cases, even >> +hours. >> >> ^3^: It is possible to use LVM on top of an iSCSI or FC-based storage. >> That way you get a `shared` LVM storage > > Ping In my experience, users mostly into issues when deleting qcow2 snapshots on NFS can take up to 10 hours. I would personally put more emphasis on this specific combination being problematic, and probably mention that in such case one should delete snapshots while the VM is offline. -- Maximiliano