From: Johan De Meersman Date: March 16 2011 7:42am Subject: Re: Suggestions for InnoDB files List-Archive: http://lists.mysql.com/mysql/224661 Message-Id: <65624346-3bee-460b-a436-64046a8289cf@zimbra> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable > From: "Adarsh Sharma" > > Johan De Meersman wrote: > > Interesting, but why like this instead of simply larger disks or raidse= ts ? > > 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 set= up. > > 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 =E2=80=93 55 percent size of hard disk.(50-55 % of 4 ha= rd 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 exac= tly 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 t= hose 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 y= ou want to lose no space at all, use RAID0 (striping) to increase performan= ce, 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 i= nsurance data loss when a disk breaks and additionally increases the read s= peed 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 m= ay fail and you'll still have all your data. Data is striped, so disk perfo= rmance also increases, although not as much as mirrorring. This is however = the most CPU-intensive form, as checksumming over all disks happens at ever= y 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 b= oost. > 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 everythi= ng 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, sav= e 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 invol= ved. Hardware RAID controllers tend to have their own specific set of metad= ata on the disks, and if your controller breaks, you had better manage to g= et the exact same one, or you risk not being able to read your disks. Sofwa= re 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 j= ust find the appropriate partitions and match the pieces together. No more = accidentally putting a disk in the wrong bay and having it break the RAIDse= t. (I'll admit that has become rare with controllers getting smarter over t= he 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. -- Bier met grenadyn Is als mosterd by den wyn Sy die't drinkt, is eene kwezel Hy die't drinkt, is ras een ezel