Date: Sun, 13 Jul 2008 19:32:36 -0400 From: Maurice Volaski <mvolaski@aecom.yu.edu> To: freebsd-questions@freebsd.org Subject: Would ZFS and gmirror work well together in a two-node failover cluster? Message-ID: <a06240401c4a03fce936c@[129.98.90.227]>
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I am looking to put together a two-node high-availability cluster where each node has identical data storage consisting of a set of internal data drives (separate from the boot drive). I want ZFS to manage the drives as a JDBOD in a RAIDZ2 configuration. Thus, if an individual drive misbehaves or fails, ZFS detects and handles the fault. But I'm also looking to mirror this entire setup in real time to a second identical server. Basically, my question is can this work well on FreeBSD while taking full advantage of ZFS? Specifically, my understanding is that the only way to handle the real time mirror is with gmirror and ggated, but it's not clear how gmirror would interact with ZFS. I am assuming that gmirror operates only on individual drives, so if I had a set of 24 drives on each server, there would be 24 mirrored drive pairs. One concern I have is that this setup could run into trouble with gmirror's potentially sabotaging ZFS's RAIDZ2. For example, when a drive starts failing, won't gmirror see it before ZFS does and take the unfavorable action of substituting the corresponding drive in the failover server in subsequent I/O, leaving ZFS's RAIDZ2 out of the loop? This is just one particular scenario, but in general, it's not entirely clear that it's possible to have fine-grained control of when, how much and in what direction gmirror manages synchronization among drive pairs. -Maurice -- Maurice Volaski, mvolaski@aecom.yu.edu Computing Support, Rose F. Kennedy Center Albert Einstein College of Medicine of Yeshiva University
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