# 3 ssd disk array, what raid level can I use?



## Darwin (Oct 24, 2014)

I am a software guy, not hardware one. Please forgive me if my question sounds stupid 


I'm thinking about renting one of those 3xssd soyoustart servers, but what I know about raid can be resumed in: raid1, 10 and that 5 is a no no for ssd.


That said and looking for data integrity, what raid options can I use in that server? Why that raid level x you recommend is the best one? I don't need mb/s neither iops porn, what ssds give by default is good enough for me.


I am looking for a soyoustart server with hardware raid, but don't mind to use soft raid if that is the best option.


Almost forgot, I plan to slice that server in a few KVMs (maybe 3-6 vms)


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## rds100 (Oct 24, 2014)

How much space do you need? If not more than the size of a single SSD, i would do a RAID1 with two SSDs and then use the third to locally store backups. Of course make remote backups too.


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## HalfEatenPie (Oct 24, 2014)

rds100 said:


> How much space do you need? If not more than the size of a single SSD, i would do a RAID1 with two SSDs and then use the third to locally store backups. Of course make remote backups too.


This is probably the best response in my opinion.  

Three is such an awkward number.


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## lowesthost (Oct 24, 2014)

Raid 1 and the 3rd drive as a hot spare


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## William (Oct 24, 2014)

RAID5 will work in SW but is not recommended for SSDs.

I personally would build a ZFS Z1.


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## Darwin (Oct 24, 2014)

rds100 said:


> How much space do you need? If not more than the size of a single SSD, i would do a RAID1 with two SSDs and then use the third to locally store backups. Of course make remote backups too.


I was aiming at least 200 gb, but can live with 120gb with raid 1.


So md raid 10 or 1e are just plain weird and sucks?



William said:


> RAID5 will work in SW but is not recommended for SSDs.
> 
> 
> I personally would build a ZFS Z1.


Thanks, going to research a bit about ZFS Z1.


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## Vijay (Oct 24, 2014)

Darwin said:


> I was aiming at least 200 gb, but can live with 120gb with raid 1.
> 
> 
> So md raid 10 or 1e are just plain weird and sucks?
> ...


There is a way to do a triple disk mirror with ZFS . This way you would keep the 3 disks in the pool... and survive 2 disk failures.. This is better than HS solution. since with HS, if during rebuild there is a failure, you would loose the data.

Also, you could create a pool with all 3 disks, and create a dataset with 'copies'=3 attribute.. That is that dataset (FS) and only that dataset has 3 copies. Depending on the space that particular dataset will be copied to 3 different disks in pool... Hence, for non-critical data, you can save space do keeping copies=1. I haven't done this myself, so I do not fully understand the data protection implications...

Check this link.. https://blogs.oracle.com/relling/entry/zfs_copies_and_data_protection

PS: all of the above are based on my experiences with Solaris & FreeBSD.. Not sure about Linux..


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## raj (Oct 24, 2014)

http://en.wikipedia.org/wiki/Standard_RAID_levels#Comparison


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## willie (Oct 24, 2014)

RAID 1 on two of the drives containing your live data.  System and temporary stuff and static files on the third drive: reinstall if it crashes.  SYS comes with 100GB of free ftp storage space, so use that to backup the non-mirrored drive.  Or if you're not running live databases, then just run without RAID and have a cron job doing rsync backups to another server (or to the ftp area) every few hours.


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## Flapadar (Oct 25, 2014)

willie said:


> RAID 1 on two of the drives containing your live data.  System and temporary stuff and static files on the third drive: reinstall if it crashes.  SYS comes with 100GB of free ftp storage space, so use that to backup the non-mirrored drive.  Or if you're not running live databases, then just run without RAID and have a cron job doing rsync backups to another server (or to the ftp area) every few hours.


Why bother? Unless he's needing 3 drives worth of data that's just wasting peace of mind.

+1 for RAID1 with hot spare.


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## Darwin (Oct 29, 2014)

Sorry to bump my old thread, but I did a few experiments and I will answer my own question about md raid 10 with 3 disks:

md raid 10 with 3 disk is meh. Didn't see any advantages, other than 50% more space than a 2 disk raid 1 (which I don't need). But speed wasn't great and only 1 disk can fail before the raid blows. (to add some context, I did that experiment using an old server using HDDs, not SSDs)

Thanks to everyone who suggested Raid 1 + a hot spare disk. This sounds the best option to what I need.


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## sshgroup (Nov 4, 2014)

you can use raid 5 but  raid 10 & one other disk better always


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## Clouvider-Dom (Apr 12, 2015)

Depending on the amount of space you need I would recommend upgrading to 4th drive and going for RAID10.

If 1x SSD size space is enough I would recommend going for RAID1. RAID5 is not recommended for SSDs due to large number of write cycles that may significantly shorten your SSD lifespan.


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## willie (Apr 12, 2015)

This is about SoYouStart, which has fixed configuraitons.  It's not possible to add a 4th drive to the 3 drive systems.


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