Re: New Linux Filesystem: NILFS

pgsql(at)j-davis(dot)com (Jeff Davis) writes:
> On Wed, 2006-09-06 at 22:12 -0400, Christopher Browne wrote:
>
>> > Can you elaborate a little? Which filesystems have been problematic?
>> > Which filesystems are you more confident in?
>>
>> Well, more or less *all* of them, on AMD-64/Linux.
>>
>> The "pulling the fibrechannel cable" test blew them all. XFS, ext3,
>> JFS. ReiserFS was, if I recall correctly, marginally better, but only
>> marginally.
>>
>> On AIX, we have seen JFS2 falling over when there were enough levels
>> of buffering in the way on disk arrays.
>
> Well, that's interesting. I suppose I can't count on the filesystem
> as much as I thought. Are you implying that the filesystems aren't
> ready on 64-bit?

I don't think this necessarily is a 64 bit issue; it's more that with
the more esoteric, expensive disk array hardware, there are fewer with
the ability to test it, because you need $200K worth of hardware
around to do the testing.

> Is it more of a hardware issue (a controller lying about the
> security of the write)? Any comments on FreeBSD/UFS+SU? I would
> expect UFS+SU to have similar issues, since it depends on write
> ordering also.
>
> What do you do for better data security (aside from the obvious
> "don't pull cables")?

The last time we looked, FreeBSD wasn't an option at all, because
there wasn't any suitable FibreChannel support. That may have
changed; haven't researched lately.

The trouble that the NILFS people pointed out seems a troublesome one,
namely that the more levels of cacheing (even if battery-backed), the
less certain you can be that the hardware isn't lying about write
ordering.

I haven't got an answer...
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