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Hi Nick, Agreed, I see your point of basically once your past the 150TBW or whatever that number maybe, your just waiting for failure effectively but aren’t we anyway? I guess it depends on your use case at the end of the day. I wonder what the likes of Amazon, Rackspace etc are doing in the way of SSD’s, either they are buying them so cheap per GB due to the “volume” or they
are possibly using “consumer grade” SSD’. hmm.. using consumer grade SSD’s it may be an interesting option if you have descent monitoring and alerting using SMART you should be able to still see how much spare flash you have available.
As suggested by Wido using multiple brands would help remove the possible cascading failure affect which I guess we all should be doing anyway on our spinners.
I guess we have to decide is it worth the extra effort in the long run vs running enterprise ssds. Regards, Quenten Grasso From: Nick Fisk [mailto:nick@xxxxxxxxxx]
Hi Quenten, There is no real answer to your question. It really depends on how busy your storage will be and particularly if it is mainly reads or writes. I wouldn’t pay too much attention to that SSD endurance test, whilst it’s great to know that they have a lot more headroom than their official spec’s, you run the risk of having a spectacular multiple
disk failure if you intend to run them all that high. You can probably guarantee that as 1 SSD starts to fail the increase in workload to re-balance the cluster will cause failures on the rest.
I guess it really comes down to how important is the availability of your data. Whilst an average pc user might balk at the price of paying 4 times per GB more for a S3700 SSD, in the enterprise
world they are still comparatively cheap. The other thing you need to be aware of is that most consumer SSD’s don’t have power loss protection, again if you are mainly doing reads and cost is more important than availability, there may be
an argument to use them. Nick From: ceph-users [mailto:ceph-users-bounces@xxxxxxxxxxxxxx]
On Behalf Of Quenten Grasso Hi Everyone, Just wondering if anyone has had any experience in using consumer grade SSD’s for a Ceph cluster? I came across this article
http://techreport.com/review/26523/the-ssd-endurance-experiment-casualties-on-the-way-to-a-petabyte/3 They have been testing different SSD’s write endurance and they have been able to write up to 1PB+ to a Samsung 840 Pro 256GB which is only “rated” at 150TBW and of course other SSD’s have failed well before 1PBW, So defiantly worth a read. So I’ve been thinking about using consumer grade SSD’s for OSD’s and Enterprise SSD’s for journals. Reasoning is enterprise SSD’s are a lot faster at journaling then consumer grade drives plus this would effectively half the overall write requirements on the consumer grade disks.
This also could be a cost effective alternative to using enterprise SSD’s as OSD’s however it seems if your happy to use 2 x replication it’s a pretty good cost saving however 3x replication not so much. Cheers, Quenten Grasso
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