Hello,
It is listed in the SANmelody Help file......see comment below.
"When either the primary or secondary virtual volume of a mirror is broken, or is in the process of recovery, (full or log-based),
all write I/Os will be acknowledged only when the storage array has acknowledged the I/O back to the storage server. This is to ensure that if a second failure should occur through the loss of a storage server or the remaining virtual volume in a mirror, then existing data is not compromised. Any read I/Os will be queried from cache first before accessing the physical disk."
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Also, If you have a configuration running you can check for yourself by using "Perfmon" to monitor "Cache Writes per/Sec" for your specific Virtual Volumes.
I can tell you from experience that it does go into write through mode (on a per Vvol basis) when a partner volume is offline, and write through for all mirror volumes if a node goes offline.
regards
Bernie.
jimboefx Wrote:I have seen the two following excellent blog articles:
http://sanmelody.blogspot.com/2008/05/cache-protection.html
http://sanmelody.blogspot.com/2008/06/ha-cluster-mirroring-explained.html#uds-search-results
Is there any official Datacore documentation to backup the processes described in these articles?
e.g. That mirror volumes go to write-thru if one partner goes offline
I can find the lock step information in the help file, but not the write-thru in event of partner offline - can you help me verify this please?
SANmelody software uses "synchronous? mirroring over the SAN, in which the write acknowledgement is not returned to the requesting server until the data has been written to both storage servers.
