Thank you for the clarification Craig, I am re-examining my storage strategy, thus my email. Sadly this machine has been in service a number of years and already contains more data than is possible in a RAID 10 configuration. If I had the spare space and resources I'd be thrilled to switch to RAID 10. That is not the case, however. Given that, I am faced with the choice between having the machine entirely unusable between now and when I can acquire a BBU or using it with the risk of data loss/corruption, I will chose the latter. Neither data loss nor corruption would go unnoticed in the period that this will be necessary.<div>
<br></div><div>Does that sound entirely unreasonable?</div><div><br></div><div>Austin<br><div><br></div><div><br></div><div><br></div><div><div><div class="gmail_quote">On Fri, Sep 2, 2011 at 10:51 AM, Craig White <span dir="ltr"><<a href="mailto:craig.white@ttiltd.com">craig.white@ttiltd.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex;">Data loss could conceivably occur on shutdown or restart too - just saying... You are assuming that the data that doesn't get written to disk is going to be non-essential... I wish you good luck with that. I think if one doesn't want to be an idiot, one would not enable a cache that has no means to ensure that the cache is written to disk.<br>
<br>
I think your take away from all of this is somewhat misdirected. Not having a BBU simply means that your writes really should always be synchronous/immediate. That shouldn't really be a problem and shouldn't impose a large performance penalty.<br>
<br>
Your performance issue relates more to the fact that RAID 5 implementation on the 3Ware cards is rather poor and modes such as RAID 10 (RAID 0 + 1) will give you much more speed that you realize. If you also consider on the surprisingly higher rates of failure with loss of data possibility when reconstructing a missing/dead drive on a RAID 5 setup you really should be re-examining your storage strategy.<br>
<br>
Craig<br>
<div><div></div><div class="h5"><br>
On Sep 1, 2011, at 5:43 PM, Austin Godber wrote:<br>
<br>
> At this point the card is pretty much useless without that cache enabled. Without recommendations for making writes of 256MB or larger files faster without this cache enabled, I will have to accept the possible data loss in the event of power outage. If it is only the case of data loss during a power outage, I will take that ... rather than failure to write at all during 99% of my usage.<br>
><br>
> I will, for the sake of not being an idiot, look into buying the BBUs.<br>
><br>
> Austin<br>
><br>
> On Thu, Sep 1, 2011 at 4:49 PM, Tom Bishop <<a href="mailto:bishoptf@gmail.com">bishoptf@gmail.com</a>> wrote:<br>
> Keep in mind you really only want to enable the cache if you have a<br>
> bbc, otherwise you are risking your data since it can/will cache<br>
> writes...just something to keep in mind.<br>
><br>
> On 9/1/11, Austin Godber <<a href="mailto:godber@gmail.com">godber@gmail.com</a>> wrote:<br>
> > Hi Craig,<br>
> ><br>
> > Thanks for the suggestion. I would if I could. I'd also probably try<br>
> > another file system. Though the good news is, enabling the write cache on<br>
> > that array has improved things significantly. Which, in my case, was:<br>
> ><br>
> > tw_cli /c2/u0 set cache=on<br>
> ><br>
> > Now, if only I had the battery backup unit for the card.<br>
> ><br>
> > Thanks, everyone for their suggestions. For now I am happy with the<br>
> > situation, but I'd be interested to hear the experiences of others.<br>
> ><br>
> > Austin<br>
> ><br>
> > On Thu, Sep 1, 2011 at 3:58 PM, Craig White <<a href="mailto:craig.white@ttiltd.com">craig.white@ttiltd.com</a>> wrote:<br>
> ><br>
> >><br>
> >> On Sep 1, 2011, at 1:41 PM, Austin Godber wrote:<br>
> >><br>
> >> > Hello,<br>
> >> ><br>
> >> > Does anyone have experience using a 3ware 9650SE series raid controller<br>
> >> on CentOS 6.0?<br>
> >> ----<br>
> >> use RAID 10<br>
> >><br>
> >> Unless something has changed, RAID 5 is notoriously slow on the 3Ware<br>
> >> controllers. Whatever you do will only incrementally speed things up. If<br>
> >> performance is desired, RAID 5 is not the way to go.<br>
> >><br>
> >> Craig<br>
> >> _______________________________________________<br>
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> >><br>
> ><br>
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