On Wed, 16 Sep 2020 at 12:12, Michael Schumacher < michael.schumacher@pamas.de> wrote:
hi,
I am planning to replace my old CentOS 6 mail server soon. Most details are quite obvious and do not need to be changed, but the old system was running on spinning discs and this is certainly not the best option for todays mail servers.
With spinning discs, HW-RAID6 was the way to go to increase reliability and speed. Today, I get the feeling, that traditional RAID is not the best option for SSDs. I am reading that all RAID members in SSD-arrays age synchronously so that the risk of a massive failure of more than one disk is more likely than with HDDs. There are many other concerns like excessive write load compared to non-raid systems, etc.
Is there any common sense what disk layout should be used these days?
I have been looking for some kind of master-slave system, where the (one or many) SSD is taking all writes and reads, but the slave HDD runs in parallel as a backup system like in a RAID1 system. Is there any such system?
I don't think so because the drives would always be out of sync but in a
restart it would be hard to know if the drive is out of sync for a good reason or a bad one. For most of the SSD raids, I have seen people just making sure to buy disks which are spec'd for more writes or similar 'smarter' enterprise trim. I have also read about the synchronicity problem but I think this may be a theory vs reality problem. In theory they should all fail at once, in reality at least for the arrays I have used for 3 years, they seem to fail in different times. that said, I only have 3 systems over 3 years with SSD drives running RAID6 so I only have anecdata versus data.
Any thoughts?
best regards Michael Schumacher
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