LVM: JFS or XFS

It's been a few months, but there was an interesting short discussion on the Linux LVM (Logical Volume Manager) mailing list. On January 15, 2004, on the Linux-LVM mailing list, Rajesh Saxena asked which file system, JFS or XFS, would be better for a file, mail, or web server that is running LVM. A number of people with extensive experience with LVM, file systems, and using them in production responded to the question. The first response was from a poster named neuron. Neuron suggested that Rajesh use ReiserFS instead of either JFS or XFS since it was designed for handling lots of small files. Also, neuron said he has had some trouble with JFS in the past. The respected and very experienced Austin Gonyou posted some comments about journaling file systems in general.

Greg Freemyer, who is also a very experienced Linux user, agreed with neuron that ReiserFS would be a good choice. Greg also suggested that if anyone uses XFS to stay away from any version earlier than 1.3.1 because earlier version ignored the sync command which could cause the lose of the journal information sitting in the disk cache. Then a user called spam, posted and added that they thought the ReiserFS tools for recovering and repairing problems were very mature if you had a file system problem. Steven Lembark chimed in that he would suggest changing the phrase, "if you have a problem" to "when you have a problem."

Rajesh posted again and thanked everyone for their suggestion of using ReiserFS which he had not considered before. Rajesh did some homework and found that XFS had some features he really liked for taking snapshots. However, Rajesh also mentioned that he had heard of some problems with ReiserFS over LVM when taking snapshots (a snapshot is a 'copy' of a file systems that is used for backups so that a live file system need not be taken off-line for backups). Heinz Mauelshagen, one the big LVM wranglers, told Rajesh that there was a LVM patch that took care of the snapshot issue with ReiserFS. Alasdair Kergon pointed out that ReiserFS snapshots for the 2.6 kernel were not yet in the kernel tree because of the switch from LVM1 to LVM2 in the 2.6 kernel. However, as you read this, the snapshot patches are in the 2.6 kernel.

This discussion is very interesting because it points out that sometimes asking about an idea you have, or asking for an opinion prior to implementation, can greatly help. Rajesh had not considered ReiserFS prior to his mailing list posting. However, after his posting he discovered that what people were suggesting was a good idea. So the moral of the story is, before implementing anything, ask for some opinions on the mailing lists (everyone know that the mailing lists are not shy about offering opinions).

Jeff Layton has been a cluster enthusiast since 1997 and spends far too much time reading mailing lists. He can found hanging around the Monkey Tree at ClusterMonkey.net (don't stick your arms through the bars though).