On 2020-02-21, Nick Holland <n...@holland-consulting.net> wrote: > On 2020-02-20 11:22, Oliver Marugg wrote: >> Hi >> >> I’ve got a Supermicro 5028D desktop server with 5 identical SATA SSDs, >> there is no HBA no RAID card in. The purpose of the server is intended >> as web/smtp and some vmm vms (os plus /home & /var storage). >> What are your suggestions or best practices configuring the device >> arrangement (eg. sofraid(4), bio(4),bioctl(4) OS 2x on 2x ssd raid1, >> data 3xssd raid5 or 1x single ssd for OS and 4x ssd raid5/10 or better >> ideas)?
You came in a bit late with the question (i.e. after you already had the hardware!). IMHO there's little use for RAID5 these days. The advantage is "more storage from a given number of drives". But that can more easily be fixed by using larger drives which are easier to recover in the event of failure. I'm not sure what level of support softraid has for stacked disciplines (it doesn't have direct RAID10 support). The boot loader only supports RAID 1 and crypto, so you will either want RAID 1 on the boot drives, or boot from USB stick etc. I think the only options that really make sense for OpenBSD are 2-drive RAID1 for main OS, and then either 2-drive RAID1 for data, plus a single drive for an extra copy of important things (I hesitate to use the word 'backup' for something in the same machine, but sometimes it can be helpful to have something that is easier to restore than your actual backups ;) - though for such a setup I would have gone with HDD rather than SSD for the 5th drive - or 3 single drives for data. > set it up as you need it... > If you think your description is anything close to specific for specific > recommendations, you need to get out more. Everything you said could > vary in demand by many orders of magnitude, except for the model number > the server...a curious thing to be specific about. > > E-mail is one of those things that's really hard to get a good backup > of, as it changes minute by minute and is considered fairly important, Dovecot replication (dsync) does a pretty good job of this actually. I think it's a much better idea than trying to backup mailboxes on an active system. Either run periodically to alternative storage on the same machine, or preferably to a different machine (preferably in a different building). > so I'd consider a three disk RAID1 for the mail store, as a disk system > failure invariably means "lost data", even with frequent backups. > Three disk RAID1 gives you a simple disk structure that can tolerate > a disk failure and still provide redundancy. (some people will tell > you that RAID1 is only two disks. These people are wrong, but often > include HW RAID controller makers. Three disk RAID1 examples are in > the man pages). Since these are SSDs and apart from random hardware failures (which aren't *so* common) the main failure mode is doing too many writes. So with three disk RAID1 the main thing you end up doing with 3 mirrored SSDs is wearing out three drives rather than two with writes at the same rate. The other risk is data corruption (either on the bus or on storage either over time - "bit rot" - or firmware bugs etc). softraid doesn't have anything to help with this (even for detection, let alone figuring out which copy of the data, if any, is correct). > As for the rest...it's a matter of how much space you need and how > much down time you can tolerate, and how you are set up to deal with > that downtime. And I'm assuming you aren't combining external and > internal services on one box. I suspect that's a bad assumption. > > And even after much careful analysis it's a bit of a guess. > Sometimes you guess wrong. So keep your design flexible and be > willing and able to say, "Well, this isn't working, let's rebuild > it with the knowledge we now have". This idea that you have to have > the perfect build the first time out is ... well, just wrong. yep :)
