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-   -   SSD raid1 vs SSD raid10 advice ? (http://www.linuxquestions.org/questions/linux-hardware-18/ssd-raid1-vs-ssd-raid10-advice-934383/)

wonker 03-14-2012 05:52 AM

SSD raid1 vs SSD raid10 advice ?
 
Hello,

I'm about to setup a mysql server and am hesitant about two different drive setups. The server will have a raid hard controller (1 Gb /s).

My supplier suggests the first one but I have seen some benchmarks that suggest that the second one would be faster :

Setup 1
Raid 1
2 drives : Intel SSD 320 MAINSTREAM "Postville Refresh" 300Gb
Maximum speeds per drive (intel site) :
Reading : 270 Mb /s
Writing : 205 Mb /s
Total setup cost : € 1,000 (499 per drive)

Setup 2
Raid 10
4 drives : Intel SSD 320 MAINSTREAM "Postville Refresh" 120Gb
Maximum seeds per drive (intel site)
Reading : 270 Mb /s
Writing : 130Mb /s
Total setup cost : € 800 (199 per drive)

Setup 2 is cheaper and the difference would allow me to get 2 SAS 1Tb drives (Raid1) for mysql logs which I have read can speed up mysql even more. (Nb : setup fees include installation, I'm not looking for other cheaper makes etc.)

I'm not sure what the speed impact of raid10 would be on small files but here is what speeds I think I could hope for (based on intels annonced speeds) on large files

420 Mb /s reading
220 Mb /s writing

What do you think ?

Thanks !

jefro 03-14-2012 04:06 PM

I think I'd run a single revodrive and make backups once in a while. I know they are expensive but if speed is what you want, they would provide that kind of real world numbers all day long.

wonker 03-16-2012 05:28 AM

Thanks,

However, I do not have this option. I only have the option between :

2 drives : Intel SSD 320 MAINSTREAM "Postville Refresh" 300Gb
4 drives : Intel SSD 320 MAINSTREAM "Postville Refresh" 120Gb
4 drives : 300 Go SAS 15k Seagate Cheetah

I know the SSD's are faster than the 15K SAS thanks to their faster response time but I'm trying to find out which solution I should go with :

Raid 1 - 2 drives : Intel SSD 320 MAINSTREAM "Postville Refresh" 300Gb

or

Raid 10 - 4 drives : Intel SSD 320 MAINSTREAM "Postville Refresh" 120Gb

cascade9 03-16-2012 07:11 AM

Quote:

Originally Posted by wonker (Post 4626461)
The server will have a raid hard controller (1 Gb /s).

Either you've made a minor mistake, you you dont want SSDs. 'b' is bit, 'B' is byte. 1Gbit/sec is 125MB/sec maximum.

I'd go for RAID5 myself. Id also be getting SLC (or maybe eMLC) SSDs over MLC. Mind you, that would cost a fair amount more....but the same thing is true of SATA vs SAS.

wonker 03-16-2012 11:47 AM

Yes I meant Giga Bytes and not Giga bits…

Raid5 is good for a web server that has alot more reads than writes but not good for mysql. A mysql server with enough memory will perform most reads from the ram and will only create tempory tables that contain text or blob on the disk. Sadly I cannot control what queries are run and lots of them are created on disk (about 30%) even though high amounts of memory have been allowed. It is therefore important that the disk can write small files very quickly.

As for the type of memory, I don't have the option, this is going to be a rented server on which I can choose what disks from a list of disks/drives.

I have continued my search on this question and have come up with the following so far :

Raid 10 with SSD's can sometimes only have the same write performance as a Raid1. This is caused by the higher latency of the extra raid level.

In this case it is better to go for Raid 1 with a model that has a 200MB/s write speed that to have a Raid10 with 4 disks that have 130Mb/s write speed as the Raid10 write speed could be less than 150MB/s. It is also a good idea to have mechanical drives for the logs as they are cheaper than SSD's and have good sequential write speeds.

I'm thinking about getting 2 300Gb SSD's for the non sequential data and 2 SAS disks (raid1) for the logs.

wonker 05-22-2012 02:42 PM

Raid 1 does not have the performance of Raid10 though…

273 05-22-2012 02:47 PM

Quote:

Originally Posted by wonker (Post 4685041)
Raid 1 does not have the performance of Raid10 though…

The spambot doesn't know that though.;)

wonker 05-23-2012 01:40 AM

Wow, I didn't know spambots were that clever…

wonker 05-23-2012 01:46 AM

Just a quick note to say that in the end I will be going with a SSD drive that has double the write speed of the initial drive and only Raid1.

There were too many ambigous articles some saying yed raid10 with SSD is great and others saying no only Raid1 with SSD. So I guess it is safer to choose the faster model and only use Raid1


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