Hi,
The ceph mds keeps all the capabilities for the files, however the
clients modify the the rados data pool objects directly (they do not do
the content modification threw the mds).
IMHO IF the file (really) gets corrupted because a client write (not
some corruption from the mds / osd) then it can only happen if:
-The first client does not request write cap (lock) for that object
before write
-OR the MDS does not store that write cap
-OR the MDS does not return the cap to the second client or refuse the
write for the second concurrent client
-OR the second client does not (request a write cap / check existing
caps / does not obey result for write request denial from the mds)
-OR any of the clients write incorrect data based on obsolete object
cache caused by missing / faulty cache eviction (Is this even possible?)
*Please correct me if I am wrong in any of the above!!*
If I were in your shoe, first I would test the locking of the cephfs by
writing two test scripts:
-One would constantly append to a file (like an SMTP server does a mailbox)
-The other would modify / add / delete parts o this file (like a imap
server does)
And wait for corruption to occur
One other thing, it would be interesting to see what the corruption
really looks like for example partially overwritten lines?
It would be interesting to know at what part of the file is the
corruption in? beginning? end? %?
Aaand if there were a mailbox compact around the corruption
Kind regards,
Denes.
On 12/11/2017 10:33 AM, Florent B wrote:
On 08/12/2017 14:59, Ronny Aasen wrote:
On 08. des. 2017 14:49, Florent B wrote:
On 08/12/2017 14:29, Yan, Zheng wrote:
On Fri, Dec 8, 2017 at 6:51 PM, Florent B <florent@xxxxxxxxxxx> wrote:
I don't know I didn't touched that setting. Which one is recommended ?
If multiple dovecot instances are running at the same time and they
all modify the same files. you need to set fuse_disable_pagecache to
true.
Ok, but in my configuration, each mail user is mapped to a single
server.
So files are accessed only by a single server at a time.
how about mail delivery ? if you use dovecot deliver a delivery can
occur (and rewrite dovecot index/cache) at the same time as a user
accesses imap and writes to dovecot index/cache.
Ok why not, but I never had problem like this with previous version of
Ceph. I will try fuse_disable_pagecache...
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