On 10/01/2014 12:38 PM, Mike Christie wrote: > On 09/30/2014 12:11 PM, Mike Christie wrote: >> On 09/24/2014 03:01 AM, Jamie Clark wrote: >>> On machines running Ubuntu 12.04 open-iscsi initiator we have noticed >>> intermittent "pdu ... rejected due to DataDigest error. (data digests >>> configured and negotiated ok on initiator and target). >>> >>> After extensive wiresharking (the problem only affects something like 1 >>> in 100000 write PDUs) I captured a failed write from the initiator and >>> found that the CRC32C value following the payload was incorrect, while >>> surrounding writes were OK. >>> >>> The target then rejects this bad pdu and follows that with an RST on the >>> TCP connection. This is expected behaviour. This seems to repeat about >>> every 10 minutes or so. >>> >>> The writes are all 4k blocks originating from iscsi-backed libvirt >>> managed KVM virtual machines. The particular failure I captured appeared >>> to be syslog data. The first 100 bytes or so of the 4k data was a syslog >>> entry, the remainder was zeroed out. >>> >>> Just wondering if digest calculation still has the potential failure >>> modes described back >>> here https://groups.google.com/d/msg/open-iscsi/OCYS5wUIYhc/Gno7edWCyH0J >>> >> >> What FS are you using and what kernel? >> >> The problem was fixed in the upper layers by default a while back for >> man file systems. Later, it was changed to a opt-in type of feature >> since it affects performance. iSCSI was not setting the correct bits to >> turn it on. I attached a patch for the current upstream kernel which >> should tell a FS to do stable pages when using iscsi data digests. >> > > Actually try the attached patch instead of the last one. It might > improve performance too. It allows us to also do zero copy sends when > data digests are enabled. >
Let me know if you are using dm-multipath over iscsi. If you are then my patch will not help. It just works for iscsi only. Looks like we also will need a fix to the dm/block layer for dm-multipath stable page support. -- You received this message because you are subscribed to the Google Groups "open-iscsi" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/open-iscsi. For more options, visit https://groups.google.com/d/optout.
