Mailinglist Archive: opensuse (1470 mails)

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Re: [opensuse] experiences with bache / logic of caching
  • From: Per Jessen <per@xxxxxxxxxxxx>
  • Date: Wed, 24 Feb 2016 16:19:43 +0100
  • Message-id: <nakhmg$1pm$>
Per Jessen wrote:

ietd uses "blockio" and "fileio" like this:

In fileio mode (default), it defines a mapping between a "Logical Unit
Number" <lun> and a given device <device> , which can be any block
(including regular block devices like hdX and sdX and virtual block
devices like LVM and Software RAID devices) or regular files.

In blockio mode, it defines a mapping between a "Logical Unit Number"
and a given block device <device>. This mode will perform direct
block i/o with the device, bypassing page-cache for all operations.
This allows for efficient handling of non-aligned sector transfers
environments) and large block transfers (media servers). This mode
works ideally with high-end storage HBAs and for applications that
either do not need caching between application and disk or need the
large block throughput.

Judging by that, blockio is the appropriate mode, but adding memory to
the storage server will not help at all.

LIO, the preferred iscsi target for openSUSE, also uses the
terms "fileio" and "blockio". I guess they're native to the iSCSI
spec. With LIO, creating a fileio backstore gives me this comment:

"Note: block backstore preferred for best results."

Per Jessen, Zürich (5.0°C) - your free DNS host, made in Switzerland.

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