From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from firstgate.proxmox.com (firstgate.proxmox.com [212.224.123.68]) by lore.proxmox.com (Postfix) with ESMTPS id D37D41FF136 for ; Mon, 23 Mar 2026 10:47:35 +0100 (CET) Received: from firstgate.proxmox.com (localhost [127.0.0.1]) by firstgate.proxmox.com (Proxmox) with ESMTP id A7EC1F867; Mon, 23 Mar 2026 10:47:52 +0100 (CET) Message-ID: Date: Mon, 23 Mar 2026 10:47:39 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [pve-devel] [PATCH docs] storage: note that qcow2 internal snapshots are inefficient From: Fiona Ebner To: pve-devel@lists.proxmox.com References: <20251128155628.223336-1-f.ebner@proxmox.com> Content-Language: en-US In-Reply-To: <20251128155628.223336-1-f.ebner@proxmox.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Bm-Milter-Handled: 55990f41-d878-4baa-be0a-ee34c49e34d2 X-Bm-Transport-Timestamp: 1774259221580 X-SPAM-LEVEL: Spam detection results: 0 AWL 0.003 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: TABGUTBTZRL7QFMQEJMFEWTXICCXABLI X-Message-ID-Hash: TABGUTBTZRL7QFMQEJMFEWTXICCXABLI X-MailFrom: f.ebner@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 X-Mailman-Version: 3.3.10 Precedence: list Reply-To: Proxmox VE development discussion List-Id: Proxmox VE development discussion List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: 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