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From:Adarsh Sharma Date:March 16 2011 9:33am
Subject:Re: Suggestions for InnoDB files
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Johan De Meersman wrote:
>> From: "Adarsh Sharma" <adarsh.sharma@stripped>
>> Johan De Meersman wrote:
>>> Interesting, but why like this instead of simply larger disks or raidsets ?
>> It's the IT-Admin Issue , I can't question that and we have only disks of 300GB (
> SAS ).
> Your admin is supposed to provide services that benefit the application you need to
> run on the server. You're stuck with the hardware, but not the setup.
>>> Why would you use 8G datafiles instead of large, partition-filling ones?
>> What is your recommendations for number of ibdata files , keeping in Mind Raid10
> is not used and the size of tables .
>> Because in RAID10 :
>> We can utilize 50 – 55 percent size of hard disk.(50-55 % of 4 hard disk
> total space if hard disks are 500 GB X 4 then we can 
>> utilize only 1 TB space from 2 TB.
> Correct. That's the price you pay for the performance and redundancy RAID10 gives
> you. Nothing is free in life :-) Incidentally, it's going to be exactly 50% - I'll be very
> interested to see where he pulls those extra 5% from.
> You could ostensibly go for RAID5, which will allow you to use 1.5 TB off those same
> four disks, at a minor loss of disk redundancy (only one may fail) and some loss of
> performance - but still better than no RAID at all. If you want to lose no space at all,
> use RAID0 (striping) to increase performance, but that offers no disk redundancy at all -
> single disk fails, you lose all data.
> As a small overview, RAID 10 gives you the benefits of striping (data for a single
> file is split over multiple disks) so reads and writes faster, AND of mirrorring (every
> block is available on multiple disks, which provides insurance data loss when a disk
> breaks and additionally increases the read speed even more. You won't actually quadruple
> the read speed, but I wouldn't be surprised to see it triple on a 4-disk RAID 10.
> RAID 5 uses one of your disks for redundancy purposes, so any single disk may fail
> and you'll still have all your data. Data is striped, so disk performance also increases,
> although not as much as mirrorring. This is however the most CPU-intensive form, as
> checksumming over all disks happens at every write. This also makes that write speed won't
> see as much benefit.
> RAID 0 has no redundancy whatsoever - if anything you could say it's worse than data
> over multiple disks, because if one disk fails the entire volume is lost. Because it
> offers striping, however, it gives performance a good boost.
>> Software RAID is not reliable on production environment because software raid is
> dependent on hardware and software both thing 
>> if one thing go down then it will not work, but in hardware raid there is no role
> of software every thing is depend on hardware.
>> But, We are not able to afford Hardware RAID.
> Maybe you shouldn't have an OS then, either; because if that fails everything is
> down? My word, if that's his excuse, I seriously recommend you get a better admin.
> Software RAID offers the same or better performance than hardware RAID, save for the
> real high-end RAID cards. Additionally it offers more flexibility in the setup - many
> combinations of RAID levels are possible, whereas the majority of controllers offer 1, 5
> and 10 at most.
> An additional benefit that is not to be laughed at, especially if you're on a budget,
> is that software RAID will work regardless of the hardware involved. Hardware RAID
> controllers tend to have their own specific set of metadata on the disks, and if your
> controller breaks, you had better manage to get the exact same one, or you risk not being
> able to read your disks. Sofware RAID, by virtue of being software, can simply be
> reinstalled on another system if need be. Tell MD to scan for and assemble RAID arrays and
> it'll just find the appropriate partitions and match the pieces together. No more
> accidentally putting a disk in the wrong bay and having it break the RAIDset. (I'll admit
> that has become rare with controllers getting smarter over the years, but I've seen
> multi-terabyte arrays go useless because some idiot operator switched two disks into the
> wrong bays)
> So, yes, my recommendation remains the same: switch the system to software RAID;
> preferably 10, 5 or 0 if you really need all that space.

A Heartiest Thanks from my heart for explaining all these things in a 
fantastic manner. I agreed with your suggestions but one thing which 
isn't explained from your side , as you go deeper in RAID point.

Q:- What is your recommendations for number of ibdata files , would it be

Make sure the disk /hdd2-1/innodb_data1 is big enough and it doesn't affect performance.

I need your help while configuring RAID10 on a Server, may be next week.

Best Regards,
Adarsh Sharma

Suggestions for InnoDB filesAdarsh Sharma16 Mar
  • Re: Suggestions for InnoDB filesJohan De Meersman16 Mar
Re: Suggestions for InnoDB filesJohan De Meersman16 Mar
  • Re: Suggestions for InnoDB filesAdarsh Sharma16 Mar
    • Re: Suggestions for InnoDB filesJohan De Meersman16 Mar
    • RE: Suggestions for InnoDB filesRolando Edwards16 Mar