Other SSD RAIDs in a workstation using MegaRAID controller

[M.E.]

Hi,

I want to setup a new home office workstation using FreeBSD.
My main requirement are low noise and large storage. Data redundancy is required as the data is intended to be stored for a long period of time, and it is mostly write once and read many -in case it matters for the RAID configuration-.

I have found that Fujitsu Esprimo P920 workstations are available at good price and they claim to be low noise.
More importantly they have 6 SATA3 connectors so that means if I understood it correctly that I can plug in 6 hard drives.

The workstation comes with an embedded RAID controller (MegaRAID) and I have been suggested in #freebsd that MegaRAID might work and that there is a megacli package to handle it. However I can not find the exact model of the controller so I understand that until it is not tested it would not be known if it works or not.

It is the first time I setup a RAID in FreeBSD (and the first time I configure a RAID in long time too):

This is the setup I am considering:

- Fujitsu Esprimo P920 with embedded MegaRAID controller
- RaidSonic ICY Dock ExpressCage
- 6x SATA SSD drives (for example SanDisk Ultra 3D SSD, SATA 2,5zoll)

And these are the questions I have:

- Can I have two small -256Gb- SSD drives to store the operating system and 4 large -2TB- SSD drives to store the data itself?
- Which RAIDs shall be configured for each one given that they are SSD?
- I have read that SSDs do not usually fail completely, and therefore I am not fully understanding if RAIDs shall be used at all -as they are geared toward entire disk failure- or if I shall use any other mean in FreeBSD?
- Is there any potential caveat or warning for using a Fujitsu Esprimo P920 in FreeBSD?
- If so, any other recommendation for FreeBSD friendly hardware for this scenario -reasonably low priced, low noise, large storage possibility- is welcomed.

Thanks,

 

[tingo]

- Can I have two small -256Gb- SSD drives to store the operating system and 4 large -2TB- SSD drives to store the data itself?

Generally, the answer is yes. The only possible problem might be if the raid controller only allows you to create just one volume (but it wouldn't be much of a raid controller then). I have no experience with MegaRAID controllers, so can't say anything about it.

- Which RAIDs shall be configured for each one given that they are SSD?

two drives can only be combined a few ways when it comes to raid.

- I have read that SSDs do not usually fail completely, and therefore I am not fully understanding if RAIDs shall be used at all -as they are geared toward entire disk failure- or if I shall use any other mean in FreeBSD?

You should be aware that raid is not a backup solution. Think of it like this: a raid solution buys you time or saves you unexpected downtime if one drive fails. But it does not protect against data rot, overwritten data etc.
For your own best interests, please have a (good) backup solution in addition to any raid setup.

 

[ralphbsz]

What tingo said: RAID only protects again disk failures (complete disk failure, and failure of one or a few sectors). It does not protect against software error (like file system self-destructing, or bugs in the RAID stack), or user errors (the infamous "rm -R"). In the real world, those are much more important sources of data loss. Well, and user errors when messing with the hardware. To protect against these other failures, you will need to set up a backup mechanism, which probably needs some sort of archiving feature, so if files are deleted (by mistake), the backup still contains them, at least for a limited amount of time.

PS, edited later: RAID also doesn't protect against site disasters, like fire or flood. Backup can protect against that, if you put it off-site.

Once you have a good backup system, the requirements on the RAID system can be relaxed, if your users can tolerate an extended outage, and loss of very recent updates. Think of it this way: Configure RAID to deal with the commonly expected failures (a single disk drive, or a few sectors). Don't waste disk space to handle uncommon failures (two disk drives failing simultaneously). Instead, when those happen, rebuild the system's hardware, and restore the most recent complete backup. In a home environment, this may be an efficient choice.

Personally, I would configure the system with a single RAID pool, using ZFS. Why ZFS? Because it is just the better file system. It has two vitally important features: Checksums that go from the file system layer all the way to the disk in a single step, and RAID that is integrated with the file system (which reduces the MTTR, thereby greatly increasing reliability). If you want good RAID resilience against disk errors, use RAID-Z2: with 6 disks, you would get 4 disks' worth of capacity. If you are willing to tolerate a complete outage and restore from backup, use RAID-Z, and you get 5 disks' worth of capacity.

Where to put the OS? The traditional answer used to be: On a separate drive. And since failure of that drive means a system outage, you need to use at least two. These days, I would just put the OS on the same ZFS RAID pool as the data.

You say "I have read that SSDs do not usually fail completely". That is not completely false: High-quality SSDs tend to not have internal metadata problems that cause complete loss of the drive; instead, as the flash chips age, they will eventually signal the inability to write, and if the user ignores that, they will eventually get sector errors. But this logic is only true for SSDs that contain high-quality internal firmware (the so-called FTL). Whether a normal household user will ever do enough writes to wear out the flash chips is a tough question. But flash wearout and internal metadata corruption is not the only real-world problem; you can also get hardware issues (chip failures, connectors and solder joints) that completely disable the drive. So yes, SSDs do occasionally fail completely.

On the question of your particular Fujitsu motherboard: I have no idea, never seen one. Whether SanDisk SSDs are good or not, I do not have enough up-to-date information. In my geography (US), I would buy Samsung, but costs can be highly different in other areas.

 

[freejlr]

A few days ago I also had the same doubts. I can't add anything more to what other users have already said.

In my case, I chose truenas, which is based on FreeBSD, so you shouldn't have many problems with the drivers since they will be practically the same ones used by FreeBSD. I wanted to share with you the question I asked in the TrueNAS forum.

As they already told you, one of the biggest problems you are going to have is the controller. You would have to use a SAS controller or in that case one that you can flash in IT mode.

In my case I chose a Dell r320 since it has a h710 mini controller which can be flashed. if you follow my thread you will see that the user in question shares a link with controllers that can be flashed. in any case, if you cannot do it, you can also buy one on ebay if you are looking for a "SAS controller freenas" will have vendors who can sell you a ready to work.

Truenas SAS

Regards.