Johan De Meersman wrote:
From: "Adarsh Sharma" <adarsh.sha...@orkash.com>
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
