[PE1950] SW- or HW-RAID for MySQL?

[eclark]

This question is incomplete, as you havent stated what your priority is, or 
how the data is to be accessed. You mentioned that it is read only, and the 
data in question is fairly large, but no indication of how often it is 
accessed, or how fast. Is the db run using replication? Are you expecting 
raid to maintain your datas integrity? How do you forsee this data to grow. 
Will traffic to/from the db increase, or stay steady? What roughly is your 
max transaction size? Is it largely done as one large query, or as a whole 
bunch of small queries across multiple tables which would be accessing 
nonsequential data from anywhere in the 100gigs of data you have? As you are 
coming from a relatively reasonable piece of hardware, I can not think your 
needs would be that drastic. I would  probably suggest running a fairly beefy 
diskserve with 73gig 15ks in a raid, handed out to your mysql server as an 
iscsi mount as you mentioned this data is read only. Further, if you 
loadbalance the dual nics in one of the higher end pe boxes, you can have 
your data served to you fairly quickly across the network. If all of the 
above is wrong and this is just a generic db, lvm may be a better choice for 
you than software raid, in  whatever box you want to go. My preference for 
lvm in this situation is only due to the ease of which you could 
expand/contract your available space, as your needs may change in the future. 
I would not suggest software raid unless you are depending on raid to keep 
your data intact, as you would be limited to higher disk sizes with faster 
spin rates and larger costs, and potentially larger access times as disk size 
increases.



On Thursday 24 August 2006 09:59 am, Tilmann.Boess at bifab.de wrote:
> Hello,
>
> we need to replace an PE2500 (2* Pentium-III 1.4 GHz) running
> Debian Sarge.   It runs a MySQL-database (about 10 GB size
> total) and a server application (many subproceses, needs a lot
> of memory and cpu power, about 100 GB data in big files).  Both
> the MySQL-database and the server application only read data
> during normal operation.  I want to put the file data into our
> SAN, but I am not decided yet what to do with the MySQL database.
> If I put the MysQL database on the internal disks, what yields
> the best performance?
> - 2.5in-10krpm disks or 3.5in-15krpm disks?
> - SW-RAID-1 or HW-RAID-1?
> I suppose that SW-RAID should be at least as fast as HW-RAID
> for our purpose, because the database is only read and not written.
> (The performance when modifying the data is not so important.)
> Therefore I want to spend our budget on cpu power and memory
> instead of an internal RAID adapter.
>
> >From the last postings in this list, I suppose that the actual
>
> Linux kernels (2.6.17.x) contains drivers for both the internal
> RAID-adapter and the internal SAS-adapter.  Is this correct or did
> I get something wrong here?  We want to install Debian Sarge on
> the new server.
>
> --
>    Dr. Tilmann Boess   (TeX: Tilmann B\"o\ss)
>    e-mail: boess at bifab.de
>
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