What is the state of iSCSI stability & performance today?


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Hello everyone!

Have anyone tried the new iSCSI target code that came with FreeBSD 10? Is it working and performing well?

I have a plan to run a replicated Microsoft SQL Server on a iSCSI LUN hosted by ZFS over 10GbE, my primary goal is to take a consistent "backup/snapshot" of the database every fifth minute. Everything else is a bonus. Is this possible?



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I am using the native iSCSI on a FreeBSD 10.1-STABLE storage to export a 200GB virtual machine to a CentOS 6.X KVM. I think the performance is quite good. The only problem I have is some warning logs regarding timeouts, but a bit of digging showed me that this is quite common on CentOS 6.X clients.



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I've been using the ctld target for some VMWare storage and it's been perfectly stable for me. Not had a blip out of it in over 6 months other than when I managed to boot up an old machine on the same IP address.

I'm using sparse files instead of ZVOLs as I've never been keen on them but you may want to test with both.

I'm no SQL server DBA so I can't say how "consistent" a backup you will get by taking a ZFS snapshot. It'll probably work but I'd want to do at least daily backups using the standard SQL server features as well.


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Thank you for letting me know. To do a consistent backup of Microsoft SQL Server I guess I have to stop it, take the snapshot and then start it again.


Aspiring Daemon

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Search for MS SQL Server and Volume Shadow Copy Service (VSS) for some additional info about snapshoting running server.


Son of Beastie

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If you can, stopping the database engine first and then doing a snapshot is the best way.