Hello Anton, Friday, April 20, 2007, 3:54:52 PM, you wrote:
ABR> To clarify, there are at least two issues with remote ABR> replication vs. backups in my mind. (Feel free to joke about the state of my mind! ;-) ABR> The first, which as you point out can be alleviated with ABR> snapshots, is the ability to "go back" in time. If an accident ABR> wipes out a file, the missing file will shortly be deleted on the ABR> remote end. Snapshots help you here ... as long as you can keep ABR> sufficient space online. If your turnover is 1 TB/day and you ABR> require the ability to go back to the end of any week in the past year, that's 52 TB. Really depends. With ZFS snapshots in order to consume 1TB by snapshot you would have deleted 1TB of files or make 1TB modification to files (or both with 1TB in SUM). There certainly are such workload. But if you just put new data (append to files, or write new files) then snapshots practically won't consume any storage. In that case it works perfectly. ABR> The second is protection against file system failures. If a bug ABR> in file system code, or damage to the metadata structures on ABR> disk, results in the master being unreadable, then it could ABR> easily be replicated to the remote system. (Consider a bug which ABR> manifests itself only when 10^9 files have been created; both ABR> file systems will shortly fail.) Keeping backups in a file system ABR> independent ABR> ABR> manner (e.g. tar format, netbackup format, etc.) protects against this. Lets say I agree. :) ABR> If you're not concerned about the latter, and you can afford to ABR> keep all of your backups on rotating rust (and have sufficient ABR> CPU & I/O bandwidth at the remote site to scrub those backups), ABR> and have sufficient bandwidth to actually move data between sites ABR> (for 1 TB/day, assuming continuous modification, that's 11 ABR> MB/second if data is never rewritten during the day, or ABR> potentially much more in a real environment) then remote replication could work. You need exactly the same bandwidth as with any other classical backup solution - it doesn't matter how at the end you need to copy all those data (differential) out of the box regardless if it's a tape or a disk. However instead of doing backup during the night, which you want to do so there will be limited impact on production performance, with replication you can do it continuously 24x7. The actual performance impact will be minimal as you should get most data from memory without touching much of disks on sending side. That also means you actually need much less throughput available to remote side. Also with frequent enough snapshoting you have your backup basically every 30 minutes or every one hour. -- Best regards, Robert mailto:[EMAIL PROTECTED] http://milek.blogspot.com _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
