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From:Warren Young Date:October 25 2010 7:02pm
Subject:Re: Is SSD suitable for mysql server?
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On 10/25/2010 3:03 AM, Johan De Meersman wrote:
>
> SSD may still be useful if you have a lot of writes, though.

Only if by "a lot" you mean "a minority".

A lone 2 TB rotating disk will beat a top-of-the-line SSD for linear 
writes, and you can beat an SSD for linear reads with a pair of disks in 
RAID-0 or -1, or four disks in RAID-10.  (Or, I suppose, some huge 
number of spindles in RAID-5 or -6, but I've never seen such an array 
big enough to be called fast at writes.)  SSDs have a clearer advantage 
for random I/O, a useful property for databases, but still, you 
shouldn't ignore the fact that SSD writes are expensive.

Therefore, you get the SSD speed benefit only if writes are rare enough 
that more data is coming off the drive at any given time than is being 
written, or if your current disk subsystem is bottlenecked by rotating 
disk head seek time, or some combination.

Since the original poster is using RAID-10, it's definitely not a sure 
deal that replacing that array with a single SSD will help.

However, it might be entertaining to benchmark it against 4 SSDs in 
RAID-10.  Or 8.  :)

> Incidentally, i'm not aware of how SSD plays with hard/software RAID setups
> - anyone know more about this ?

Some software RAID and RAID-like systems are gaining SSD awareness so 
they can intentionally place frequently-accessed data on the SSD.
Thread
Is SSD suitable for mysql server?wroxdb25 Oct
  • Re: Is SSD suitable for mysql server?Johan De Meersman25 Oct
    • Re: Is SSD suitable for mysql server?Glyn Astill25 Oct
      • Re: Is SSD suitable for mysql server?Warren Young25 Oct
      • RE: Is SSD suitable for mysql server?Daevid Vincent25 Oct
        • RE: Is SSD suitable for mysql server?Glyn Astill26 Oct
    • Re: Is SSD suitable for mysql server?Warren Young25 Oct
      • Re: Is SSD suitable for mysql server?Joerg Bruehe26 Oct
  • Re: Is SSD suitable for mysql server?mos26 Oct