On Sat, 26 Jun 2010, Shaochun Wang wrote:
Hi: Recently I heard of the so called "write hole" problem of raid5 in Linux software raid. I use ext4 filesystem on my NAS, which assembles data disks using Linux software raid. So I wonder how safe my such system!
RAID is never a replacement for backups, corruption can happen at multiple levels in your system for different reasons. Non-ECC memory can have bit flips which corrupts your data, write hole can cause data corruption, etc.
Generally, unless you have really really high demands on data integrity, this is not a major problem.
Ext4 has other potential software/fs interactions when it comes to data integrity, in that it write buffers for quite some time, so even if you think your file is saved, it might take many seconds before it's actually on disk if your software doesn't fsync() it. Most don't, because Ext3 took so long to do it.
So generally, don't worry too much, but make sure you have backups for your important data.
-- Mikael Abrahamsson email: swmike@xxxxxxxxx -- To unsubscribe from this list: send the line "unsubscribe linux-raid" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
