[ec2-beta] data corruption
mark at ubuntu.com
Tue Apr 14 21:58:21 BST 2009
I'll ask Pete Graner, who leads the Ubuntu kernel team, for a definitive
statement (or a pointer to the person who can provide it :-)).
John Hampton wrote:
> Hi Mark,
> Interesting information about file system preferences. I was wondering
> what is the status of XFS? We use it because of the quicker time to
> On Tue, Apr 14, 2009 at 12:54 PM, Mark Shuttleworth <mark at ubuntu.com
> <mailto:mark at ubuntu.com>> wrote:
> Ben Hendrickson wrote:
>> I use around 16 large instances for data processing tasks. When using
>> the beta AMIs, I had around a dozen instances of data corruption.
>> Previously when using the alestic.com <http://alestic.com> images, and now that I've
>> switched back to them, I haven't seen any corruption. Is there any
>> known issue this could be related to?
>> I use machines by raiding together the disks via RAID 0, and then
>> installing ReiserFS on top of that. The list of commands I use to do
>> this is at the bottom of this email. The workload of the machines
>> changes somewhat, but generally it maxes out both of the cores, use
>> around 15MB/s of disk throughput (split even read/writing), and has
>> the disks around 60% full. Our data is always compressed on disk
>> (LZO), and we have checksums every 64KB of uncompressed data. What I
>> would see is that at a seemingly random point in a file the checksum
>> wouldn't match, although the checksums for the rest of the file both
>> before and after this point would be fine. I didn't notice anything
>> unusual in the system logs.
> Thanks for the detailed information, that may help to narrow the
> search for the problem substantially.
> Is ReiserFS integral to the solution, or a personal preference? It
> jumped out at me as an area of risk, as it's not a filesystem
> we're particularly focused on. Ext3, and the newer ext4 and
> ultimately btrfs would be the "stable, next, future" default
> filesystems we'd recommend unless there was a specific technical
> reason to do otherwise. If Reiser isn't integral I'd be interested
> in your results with ext3, both performance and stability wise.
> There are different kernels, as I understand it, between the
> Alestic images. Chuck and Eric will be able to say in detail but
> AIUI the beta AMI's use newer kernels, which bring some benefits
> but are also quite possibly the source of new gotchas. You may
> have triggered one of those.
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