about ceph new read-ahead feature : https://github.com/ceph/ceph/commit/a9f302da08ab96128b28d85e2f566ad0f2ba2f30
+ + +Read-ahead Settings +======================= + +.. versionadded:: 0.86 + +RBD supports read-ahead/prefetching to optimize small, sequential reads. +This should normally be handled by the guest OS in the case of a VM, +but boot loaders may not issue efficient reads. +Read-ahead is automatically disabled if caching is disabled. + + +``rbd readahead trigger requests`` + +:Description: Number of sequential read requests necessary to trigger read-ahead. +:Type: Integer +:Required: No +:Default: ``10`` + + +``rbd readahead max bytes`` + +:Description: Maximum size of a read-ahead request. If zero, read-ahead is disabled. +:Type: 64-bit Integer +:Required: No +:Default: ``512 KiB`` + + +``rbd readahead disable after bytes`` + +:Description: After this many bytes have been read from an RBD image, read-ahead is disabled for that image until it is closed. This allows the guest OS to take over read-ahead once it is booted. If zero, read-ahead stays enabled. +:Type: 64-bit Integer +:Required: No +:Default: ``50 MiB`` So, It's important to setup : rbd readahead disable after bytes=0 for proxmox backups ----- Mail original ----- De: "Dietmar Maurer" <diet...@proxmox.com> À: "Alexandre DERUMIER" <aderum...@odiso.com> Cc: pve-devel@pve.proxmox.com, "VELARTIS Philipp Dürhammer" <p.duerham...@velartis.at>, "Dmitry Petuhov" <mityapetu...@gmail.com> Envoyé: Samedi 18 Octobre 2014 09:47:08 Objet: RE: [pve-devel] backup ceph high iops and slow > >>We read 64K blocks, so > > Don't for for backup, but drive-mirror have a "granulary" option to change > the > block size: > > # @granularity: #optional granularity of the dirty bitmap, default is 64K. > # Must be a power of 2 between 512 and 64M. Although it would be much easier it read-ahead solve the problem ;-) Anybody have newest ceph with those read-ahead patches for testing? _______________________________________________ pve-devel mailing list pve-devel@pve.proxmox.com http://pve.proxmox.com/cgi-bin/mailman/listinfo/pve-devel
