# gjournal reliability & robustness?



## skyhawk (Nov 24, 2008)

Heya,

So I find myself setting up a new light-duty server machine. I've got a pair of 500G SATA drives I'm planning to mirror. I just became aware of gjournal.

Because I've had problems in the past with vinum (Which became not-production-ready in 6.0 without the documentation stating so) I feel the need to ask - Who here is using gjournal, for what kind of applications, and does it work well?


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## kamikaze (Nov 24, 2008)

You might be talking about gmirror, which has a very good reputation. Gjournal is a journaling layer that can be used with UFS.


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## skyhawk (Nov 24, 2008)

Nope, I'm talking about gjournal. I've used gmirror quite a bit, and I'm very happy with it - as well as graid3. gjournal is new to me though, and that's what I'm looking for anecdotal evidence for.


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## tanked (Nov 24, 2008)

I use gjournal on my RAID-0 array and I've had no problems with it, though I am talking about my home machine and the array has fairly low usage. I think gjournal is a godsend though, on the odd occasion when the power goes I don't have to wait for fsck to check my array and slow my machine down. However, the few benchmarks I've looked at seem to show you'll get better performance with softupdate.


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## lme@ (Nov 24, 2008)

tanked said:
			
		

> I use gjournal on my RAID-0 array and I've had no problems with it, though I am talking about my home machine and the array has fairly low usage. I think gjournal is a godsend though, on the odd occasion when the power goes I don't have to wait for fsck to check my array and slow my machine down. However, the few benchmarks I've looked at seem to show you'll get better performance with softupdate.



You know that RAID-0 is the worst thing you can do?
If one of your HDD fails, you lose all your data.
If your controller fails, you lose all your data.
If your mainboard fails, you most probably cannot use the HDDs with another mainboard...


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## DutchDaemon (Nov 24, 2008)

RAID0 is fine, depending on how expendable your data is, or on how often you backup non-expendable data. It's fast, and that's what usually counts for those who use it.


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## tanked (Nov 24, 2008)

lme@ said:
			
		

> You know that RAID-0 is the worst thing you can do?
> If one of your HDD fails, you lose all your data.
> If your controller fails, you lose all your data.
> If your mainboard fails, you most probably cannot use the HDDs with another mainboard...



Yes, as DutchDaemon says, my data is expendable and also backed up using Bacula anyway. I use RAID-0 for the performance.


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## Mel_Flynn (Nov 24, 2008)

skyhawk said:
			
		

> Nope, I'm talking about gjournal. I've used gmirror quite a bit, and I'm very happy with it - as well as graid3. gjournal is new to me though, and that's what I'm looking for anecdotal evidence for.



gjournal is very good for squid (preferred even). Also good for machines prone to power failures since background_fsck is not advised (search various mailing lists on the topic, including -questions and -fs) and start up time needs to be minimized.
ZFS is the upgrade to both gjournal and gmirror, but has had a lot less real world testing then those, plus requires memory.

gjournal is something to think twice about in combination with ACID compliant databases, as the filesystem will lie about sync. In practice, it's not a big issue. You just need to consider that commits that are recorded as comitted, can remain in the journal before actually being synced to disk.

Overall, gjournal has the best performance enhancement on write intensive applications.


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## Djn (Nov 24, 2008)

If this is amd64, you might want to look at ZFS as well - it can do mirroring, and doesn't require a fsck after an unclean shutdown. As for stability you'll have to ask someone else, but I have the impression it's usable.

edit: As above, yes - he posted while I was typing, apparently.


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