Hello all,
This suggestion is not about storing the journal on a separate device.
Many of the tasks on an Ext4 file-system require a full or massive scan
of the metadata. A few examples:
- backup: you need to get a list with all "mtime" or "size" changed
files since last backup
- reporting: you need to get a list with all files of a particular
"group" owner ID
- delete: deleting the "/home/$user" of someone with lots of data and files
I know many efforts have been made to make the (meta)data operations
"local" -- this speeds up spinning disks operations a lot, also SSD
ones. However, having the whole metadata on an SSD disk (or a RAID1 of
two such disks) could speed up many common tasks a lot. And the hardware
price for such a benefit is really affordable now.
I see two possible implementations:
1. Re-work the Ext4 metadata operations (that work with inodes, etc) to
read/write on a separate block device.
or
2. Add an option to the "data locality" algorithm to force it to store
all metadata only at the beginning of a device (we can pre-allocate
enough space). We can then transparently map in the DM those blocks to a
separate faster block device, thus making the changes to Ext4 minimal.
Does all this make sense, or I'm missing something obvious?
Thank you for your time.
--
Best regards.
Ivan Zahariev | System Administrator | ICDSoft Ltd.
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