[pbs-devel] [PATCH proxmox-backup] docs: s3: extend recommendations and limitations for local cache

[pbs-devel] [PATCH proxmox-backup] docs: s3: extend recommendations and limitations for local cache

[Christian Ebner]

Specify that the local cache must be a dedicated storage, it cannot
reuse pre-existing datastores. Further, give some more
recommendations about size and clarify that storage backed by
volatile memory cannot be used for this, at least for the time being.

Signed-off-by: Christian Ebner <c.ebner@proxmox.com>
---
 docs/storage.rst | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/docs/storage.rst b/docs/storage.rst
index ef6eb7657..54540219b 100644
--- a/docs/storage.rst
+++ b/docs/storage.rst
@@ -288,11 +288,14 @@ To list your s3 endpoint configuration, run:
    # proxmox-backup-manager s3 endpoint list
 
 A new datastore with S3 backend can be created using one of the configured S3 endpoints. Although
-storing all contents on the S3 object store, the datastore requires nevertheless a local cache store,
-used to increase performance and reduce the number of requests to the backend. For this, a local
-filesystem path has to be provided during datastore creation, just like for regular datastore setup.
-A minimum size of a few GiB of storage is recommended, given that cache datastore contents include
-also data chunks.
+storing all contents on the S3 object store, the datastore requires nevertheless a local persisant
+cache, used to increase performance and reduce the number of requests to the backend. For this, a
+local filesystem path has to be provided during datastore creation, just like for regular datastore
+setup. However, unlike for regular datastores the size of the local cache can be limited, 64 GiB to
+128 GiB are recommended given that cached datastore contents include also data chunks. Best is to
+use a dedicated disk, partition or ZFS dataset with quota as local cache. Note however, it is not
+possible to use a pre-existing regular datastore for this. Further, the use of volatile memory only
+for the cache is currently not possible.
 
 To setup a new datastore called ``my-s3-store`` placed in a bucket called ``pbs-s3-bucket``, run:
 
-- 
2.47.2



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[pbs-devel] applied: [PATCH proxmox-backup] docs: s3: extend recommendations and limitations for local cache

[Thomas Lamprecht]

On Thu, 31 Jul 2025 09:09:45 +0200, Christian Ebner wrote:
> Specify that the local cache must be a dedicated storage, it cannot
> reuse pre-existing datastores. Further, give some more
> recommendations about size and clarify that storage backed by
> volatile memory cannot be used for this, at least for the time being.
> 
> 

Applied, thanks!

[1/1] docs: s3: extend recommendations and limitations for local cache
      commit: 20c9b998baefb8aec7bb0a4afa2a3d7ab06279c3


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