User: Password:
|
|
Subscribe / Log in / New account

Improving ext4: bigalloc, inline data, and metadata checksums

Improving ext4: bigalloc, inline data, and metadata checksums

Posted Nov 30, 2011 21:05 UTC (Wed) by walex (subscriber, #69836)
In reply to: Improving ext4: bigalloc, inline data, and metadata checksums by ebirdie
Parent article: Improving ext4: bigalloc, inline data, and metadata checksums

Sparse VM virtual disks are usually a very big performance mistake. There is always the option to have VM virtual disks as logical volumes under LVM2, which usually is enormously better than as large files under any filesystem.


(Log in to post comments)

Improving ext4: bigalloc, inline data, and metadata checksums

Posted Dec 1, 2011 23:04 UTC (Thu) by job (guest, #670) [Link]

Did you benchmark that? I tried it once under VMware and I was surprised to find out that the opposite was true. It may of course have been a fluke or a result of some VMware-specific behaviour and I did not pursue it further. I'm just interested in your findings.

Improving ext4: bigalloc, inline data, and metadata checksums

Posted Dec 3, 2011 0:34 UTC (Sat) by walex (subscriber, #69836) [Link]

I had to completely re-vase a set of virtual machines that were installed by some less thoughtful predecessor into growable VMware virtual disks. Several virtual disks had several hundred thousand extents (measured with filefrag) and a couple had over a million, all mixed up randomly on the real disk. Performance was horrifying (it did not help that there were another two absurd choices in the setup).

I ended up with just the mostly readonly filesystem in the VM disk, and all the writable subtrees mounted via NFS from the host machine, which was much faster. In particular during backups, because I could run the backup program (BackupPC based on RSYNC) on the real machine and remote backup is a very high IO load operation, and running it inside the virtual machines on a virtual disk was much much slower.

Improving ext4: bigalloc, inline data, and metadata checksums

Posted Dec 6, 2011 21:26 UTC (Tue) by job (guest, #670) [Link]

Sorry, I didn't type that clearly. I meant using LVM volumes as virtual disks, not using sparse virtual disks.


Copyright © 2017, Eklektix, Inc.
Comments and public postings are copyrighted by their creators.
Linux is a registered trademark of Linus Torvalds