Mirroring Boot Disk

[Dlweeksjr]

OK, I see how to do it but how costly is it? Memory, CPU? We have Netra 240's with dual 73G hard drives. Management wants to consider disk mirroring. My inclination is to decline as I am afraid the overhead of SDS could be expensive. The disk is used not only for boot but for operations and most of our applications are doing near-real time response stuff. Also, one partition holds the database, logs and other files which change rapidly. Failover would be nice to have but any one have a guage for the costs? BTW, Is journaling/logging acceptable on a mirrored volumes?
Don

 

[daFranze]

the rule of thumb is: mirroring is about 90% write speed (parallel writing, recommended if disks are connected to different controllers vs. serial Writing, which is even slower than 90%) and 110% read speed (round robbin vs geometric, but since you only have 2 disks this is nothing of heavy impact)

>> BTW, Is journaling/logging acceptable on a mirrored volumes?

yes, you mean Filesystem logging, the mountoption: if your host crashes and the FS is damaged the fsck may take some time on large FS -> recommeded to do logging

I suggest to setup the Machine using only one disk (you can create the metadevices but just add one side of the metamirror), mount logging and do some performancetests; add the second metamirror and wait for the resyncs (check metastat) and perform the same tests; can you see some performance impact?

Mirroring is only necessary to increase uptime (system does not crash if one of the disks is no longer available), what is the impact to your enterprise if this host is not available? What do you need speed or availability, or both? ;0)

Regards
-- Franz
Sorry I'm not a native spaeker, I'm from Munich, Germany - "Home of the Whopper", oh no, "Home of the Oktoberfest" ;-)
Solaris System Manager; I used to work for Sun Microsystems Support (EMEA) for 5 years