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I'm looking at the DELL PowerEdge™ R720 from Hetzner.

This server has a Dell PERC H710 8 Port SAS/SATA 6GBit/s raid controller.

I have the choice between:

  • 3 x 600GB SSD (MLC SATA 3Gb/sec)
  • 6 x 600GB 15k rpm SAS disks

The price between both options are the same.

I need at least 1,2 TB of disk space, more is better.

The server will be used to host ESX 5 development machines. Mostly heavy reads, not that many writes.

Which option would be more performant?

With the 6 x 600GB SAS disks I would also have the possibility to put them in RAID 10 (and of course RAID 5). With the SSD's it will be RAID 5.

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No, NEVER use RAID 5 with SSDs. And run far away from Hetzner. – Michael Hampton Jun 7 '13 at 8:14
@MichaelHampton Can you explain your comment? In this way nobody knows why to do your advise. – Uwe Plonus Jun 7 '13 at 8:15
@UwePlonus If you use RAID 5 with SSDs, they are written to continuously and wear out in as little as a few weeks. Goodbye data. And Hetzner... well you can google "Hetzner sucks" for that. – Michael Hampton Jun 7 '13 at 8:18
See this answer for why RAID5 isn't so bad after all. @MichaelHampton, it's pure FUD to say SSDs will wear out in weeks in a RAID5. – Daniel Lawson Jun 7 '13 at 8:26
@DanielLawson Fair enough, though the write amplification is still a significant issue to be aware of. – Michael Hampton Jun 7 '13 at 8:32
up vote 2 down vote accepted

RAID 10 is better for databases. Even though you'll be heavier on reads, caching and changes to the actual database will still impact the performance of your server.

I would go with the 6x SAN disks. SSDs in RAID 5 is just asking for trouble since you only have a single drive tolerance, and SSDs tend to fail rather suddenly where spinning drives tend to have warning signs.

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