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From Dor Laor <...@scylladb.com>
Subject Re: EC2 instance recommendations
Date Tue, 23 May 2017 18:14:18 GMT
Note that EBS durability isn't perfect, you cannot rely on them entirely:
https://aws.amazon.com/ebs/details/
"Amazon EBS volumes are designed for an annual failure rate (AFR) of
between 0.1% - 0.2%, where failure refers to a complete or partial loss of
the volume, depending on the size and performance of the volume. This makes
EBS volumes 20 times more reliable than typical commodity disk drives"
It's rare but once in awhile we get an email notification that one of our
EBS drives was corrupted.
In this case a combined write through cache and EBS is certainly better
than EBS w/o backup.



On Tue, May 23, 2017 at 10:40 AM, Jonathan Haddad <jon@jonhaddad.com> wrote:

> Another option that I like the idea of but never see used unfortunately is
> using ZFS, with EBS for storage and the SSD ephemeral drive as L2Arc.
> You'd get the performance of ephemeral storage with all the features of
> EBS.  Something to consider.
>
> On Tue, May 23, 2017 at 10:30 AM Gopal, Dhruva <Dhruva.Gopal@aspect.com>
> wrote:
>
>> Thanks! So, I assume that as long we make sure we never explicitly
>> “shutdown” the instance, we are good. Are you also saying we won’t be able
>> to snapshot a directory with ephemeral storage and that is why EBS is
>> better? We’re just finding that to get a reasonable amount of IOPS (gp2)
>> out of EBS at a reasonable rate, it gets more expensive than an I3.
>>
>>
>>
>> *From: *Jonathan Haddad <jon@jonhaddad.com>
>>
>>
>> *Date: *Tuesday, May 23, 2017 at 9:42 AM
>> *To: *"Gopal, Dhruva" <Dhruva.Gopal@Aspect.com>, Matija Gobec <
>> matija0204@gmail.com>, Bhuvan Rawal <bhu1rawal@gmail.com>
>>
>> *Cc: *"user@cassandra.apache.org" <user@cassandra.apache.org>
>>
>>
>> *Subject: *Re: EC2 instance recommendations
>>
>>
>>
>> > Oh, so all the data is lost if the instance is shutdown or restarted
>> (for that instance)?
>>
>>
>>
>> When you restart the OS, you're technically not shutting down the
>> instance.  As long as the instance isn't stopped / terminated, your data is
>> fine.  I ran my databases on ephemeral storage for years without issue.  In
>> general, ephemeral storage is going to give you lower latency since there's
>> no network overhead.  EBS is generally cheaper than ephemeral, is
>> persistent, and you can take snapshots easily.
>>
>>
>>
>> On Tue, May 23, 2017 at 9:35 AM Gopal, Dhruva <Dhruva.Gopal@aspect.com>
>> wrote:
>>
>> Oh, so all the data is lost if the instance is shutdown or restarted (for
>> that instance)? If we take a naïve approach to backing up the directory,
>> and restoring it, if we ever have to bring down the instance and back up,
>> will that work as a strategy? Data is only kept around for 2 days and is
>> TTL’d after.
>>
>>
>>
>> *From: *Matija Gobec <matija0204@gmail.com>
>> *Date: *Tuesday, May 23, 2017 at 8:15 AM
>> *To: *Bhuvan Rawal <bhu1rawal@gmail.com>
>> *Cc: *"Gopal, Dhruva" <Dhruva.Gopal@Aspect.com>, "
>> user@cassandra.apache.org" <user@cassandra.apache.org>
>> *Subject: *Re: EC2 instance recommendations
>>
>>
>>
>> We are running on I3s since they came out. NVMe SSDs are really fast and
>> I managed to push them to 75k IOPs.
>>
>> As Bhuvan mentioned the i3 storage is ephemeral. If you can work around
>> it and plan for failure recovery you are good to go.
>>
>>
>>
>> I ran Cassandra on m4s before and had no problems with EBS volumes (gp2)
>> even in low latency use cases. With the cost of M4 instances and EBS
>> volumes that make sense in IOPs, I would recommend going with more i3s and
>> working around the ephemeral issue (if its an issue).
>>
>>
>>
>> Best,
>>
>> Matija
>>
>> On Tue, May 23, 2017 at 2:13 AM, Bhuvan Rawal <bhu1rawal@gmail.com>
>> wrote:
>>
>> i3 instances will undoubtedly give you more meat for buck - easily 40K+
>> iops whereas on the other hand EBS maxes out at 20K PIOPS which is highly
>> expensive (at times they can cost you significantly more than cost of
>> instance).
>>
>> But they have ephemeral local storage and data is lost once instance is
>> stopped, you need to be prudent in case of i series, it is generally used
>> for large persistent caches.
>>
>>
>>
>> Regards,
>>
>> Bhuvan
>>
>> On Tue, May 23, 2017 at 4:55 AM, Gopal, Dhruva <Dhruva.Gopal@aspect.com>
>> wrote:
>>
>> Hi –
>>
>>   We’ve been running M4.2xlarge EC2 instances with 2-3 TB of storage and
>> have been comparing this to I-3.2xlarge, which seems more cost effective
>> when dealing with this amount of storage and from an IOPS perspective. Does
>> anyone have any recommendations/ on the I-3s and how it performs overall,
>> compared to the M4 equivalent? On the surface, without us having taken it
>> through its paces performance-wise, it does seem to be pretty powerful. We
>> just ran through an exercise with a RAIDed 200 TB volume (as opposed to a
>> non RAIDed 3 TB volume) and were seeing a 20-30% improvement with the
>> RAIDed setup, on a 6 node Cassandra ring. Just looking for any
>> feedback/experience folks may have had with the I-3s.
>>
>>
>>
>> Regards,
>>
>> *DHRUVA GOPAL*
>>
>> *sr. MANAGER, ENGINEERING*
>>
>> *REPORTING, ANALYTICS AND BIG DATA*
>>
>> *+1 408.325.2011 <+1%20408-325-2011>* *WORK*
>>
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>>
>> *UNITED STATES*
>>
>> *dhruva.gopal@aspect.com <dhruva.gopal@aspect.com> *
>>
>> *aspect.com <http://www.aspect.com/>*
>>
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>>
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