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I like to have best io performance as well as good capaciyy and reliability out of a server that hosts a busy forum, which involves loads of static files download. I am wondering what is the best plan to format and use the disks given that the server has only 4 disk bays and I have 2 SSD and 2 SATA disks at hand. I am currently thinking about putting the disks in RAID 10 so that SSD contains /var/lib/mysql as well as most of the OS (Likely to be Debian) and SATA disk to contain /path/to/static/files. However I'd like to hear your expert opinion on this. Thanks

alfish
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  • If you are already hosting a busy forum, then it should be easy for you to collect some data about how your storage is being used. Once you have that data, then you can some up with some tests that will permit you to try things on your additional drives. – Zoredache Oct 02 '12 at 20:07
  • possible duplicate of [What are the different widely used RAID levels and when should I consider them?](http://serverfault.com/questions/339128/what-are-the-different-widely-used-raid-levels-and-when-should-i-consider-them) – Michael Hampton Oct 07 '12 at 13:52

3 Answers3

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Best I/O performance?

  • RAID0 consisting of 2x SSDs - for MySQL, WWW root dir
  • RAID0 consisting of 2x SATA - for larger files, logs, os

Not at all recommended. RAID0 isn't RAID at all

Best I/O safety?

  • RAID1 consisting of 2x SSDs - for MySQL, WWW root dir
  • RAID1 consisting of 2x SATA - for larger files, logs

Realistically, the best and easiest to manage option. Someone of your ability should do this.

Best I/O performance and safety?

  • RAID1 consisting of 2x SATA - for everything
  • RAID1 consisting of 2x SSDs - mounted using bcache/flashcache to underpin the SATA array

More tricky to configure, but could reap benefits of the HOT SSD storage

OR if you are feeling more creative/brave

  • RAID10 stripe consisting of
    • RAID1 of 1x SATA and 1x SSD - using --write-behind/--write-mostly as appropriate
    • RAID1 of 1x SATA and 1x SSD - using --write-behind/--write-mostly as appropriate

You'd have to be mad to do this

Ben Lessani
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  • I'm not familiar with bcache/flashcache option. Would you please elaborate a bit on this and possibly refer me to relevant references to set that up? – alfish Oct 02 '12 at 20:30
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    @alfish No. Its far beyond the scope of answering this question. You'd be better off creating a new question - but even then, given you don't have the most basic understanding of it - its not worth the effort. Someone would have to hand-hold your throughout the entire set-up - and that's **not** what SF is about. – Ben Lessani Oct 02 '12 at 20:34
  • OK, so which one is your own prefered solution? – alfish Oct 02 '12 at 20:39
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Put the SATA disks in a RAID 1. Put the SSDs in a RAID 1. There's no other viable option in a standard server with 4 bays where 2 disks are SSD and 2 are not.

I am currently thinking about putting the disks in RAID 10

No.

No. No. No. No. No. No. No.

MDMarra
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  • Alright, and how should I distribute Linux failesystem on the two RAID 1 disks? – alfish Oct 02 '12 at 20:10
  • Put your busiest data (/var maybe?) on the SSD. I'm not a mind reader, I have no idea what files are your busiest and what part of the filesystem they are in. – MDMarra Oct 02 '12 at 20:11
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If you got the SSD's for the speed only, and with no important data on them, you could put them in RAID0. Then you could use your SATA disks in RAID1 as backup if the SSD's fails.

This will give you some nice speeds, and still have your data secured on the RAID1.

Frederik
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