|To:||Dave Chinner <david@xxxxxxxxxxxxx>|
|Subject:||Re: understanding speculative preallocation|
|From:||Jason Rosenberg <jbr@xxxxxxxxxxxx>|
|Date:||Fri, 26 Jul 2013 13:40:16 -0400|
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Thanks for your responses. I'm a bit confused, as I didn't see your responses on the actual forum (only in my email inbox).
Anyway, I'm surprised that you don't have some list or other way to correlate version history of XFS, with os release versions. I'm guessing the version I have is not using the latest/greatest. We actually have another system that uses an older version of the kernel (2.6.32-279), and it behaves differently (it still preallocates space beyond what will ever be used, but not by quite as much). When we rolled out our newer machines to 2.6.32-358, we started seeing a marked increase in disk full problems.
If, say you tell me, the mainline xfs code has improved behavior, it would be nice to have a way to know which version of CentOS might include that? Telling me to read source code across multiple kernel versions sounds like an interesting endeavor, but not something that is the most efficient use of my time, unless there truly is no one who can easily tell me anything about xfs version history.
Do you have any plans to have some sort of improved documentation story around this? This speculative preallocation behavior is truly unexpected and not transparent to the user. I can see that it's probably a great performance boost (especially for something like kafka), but kafka does have predictable log file rotation capped at fixed sizes, so it would be great if that could be factored in.
I suppose using the allocsize setting might work in the short term. But I probably don't want to set allocsize to 1Gb, since that would mean every single file created would start with that size, is that right? Does the allocsize setting basically work by always keeping the file size ahead of consumed space by the allocsize amount?
On Fri, Jul 26, 2013 at 7:50 AM, Dave Chinner <david@xxxxxxxxxxxxx> wrote:
On Fri, Jul 26, 2013 at 12:23:40AM -0700, jbr wrote:
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