-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Mark Perry wrote: | | The Linux Kernel defaults to not using "barriers", but SLES has a patch | to enable it by default.
Just a couple of thoughts, and information from the article. Note the default above is a filesystem flag. You can turn this on in all your mounts by hand, also. However, be aware this flag is valueless if you're running a filesystem on top of LVM. This is what the article has to say about it: | It turns out that the "getting away with it" factor is not just luck. Ted Ts'o explains what's going on: the journal on ext3/ext4 filesystems is normally contiguous on the physical media. The filesystem code tries to create it that way, and, since the journal is normally created at the same time as the filesystem itself, contiguous space is easy to come by. Keeping the journal together will be good for performance, but it also helps to prevent reordering. In normal usage, the commit record will land on the block just after the rest of the journal data, so there is no reason for the drive to reorder things. The commit record will naturally be written just after all of the other journal log data has made it to the media. | | That said, nobody is foolish enough to claim that things will always happen that way. Disk drives have a certain well-documented tendency to stop cooperating at inopportune times. Beyond that, the journal is essentially a circular buffer; when a transaction wraps off the end, the commit record may be on an earlier block than some of the journal data. And so on. So the potential for corruption is always there; in fact, Chris Mason has a torture-test program which can make it happen fairly reliably. There can be no doubt that running without barriers is less safe than using them. | Often, once these issues come to light in the linux kernel community, some solutions or another follows. I'm rather hoping that will also be the case for this one. - -- Pat -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.7 (Darwin) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org iD8DBQFIPBnpNObCqA8uBswRAkcoAJ9/PL0hhnzy2tP5TmWVjM1M4r9KiQCeM3Xv VPrO6T4Pu5pPByRlQeQHzaI= =4FnQ -----END PGP SIGNATURE----- ---------------------------------------------------------------------- For LINUX-390 subscribe / signoff / archive access instructions, send email to [EMAIL PROTECTED] with the message: INFO LINUX-390 or visit http://www.marist.edu/htbin/wlvindex?LINUX-390
