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RAID with SSDs on SQL server

Posted on 2013-06-17
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Hi,

I've built a server using two raids - one with SAS drives and the other with SSD drives where the SQL DB resides.

My questions is whether RAID5 on SSD for Samsung 840 Pro drives is enough. I have recently researched more into this and they suggest to have a hot spare in this case but my server doesn't have any space left so that's out of the question.

What would be better option? Leave it as RAID5 or move to RAID 6 or RAID1+0?

Reading speed is very important as it's SQL server but security of the data is essential.

I run ShadowProtect to a SAN every 15 minutes on Dell PE R710
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Question by:JurajUQU
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by:dlethe
ID: 39254827
Are you using the Dell certified SSDs, or your own? on the RAID controller?
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by:JurajUQU
ID: 39254845
my own SSDs - Samsung 840 Pro on RAID controller
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by:dlethe
ID: 39254848
But regardless of the controller, since this is important data and you want stability/availability, in addition to speed ...
1) take the SSDs out of the RAID controller.  Use a decent SATA card and native windows software RAID1 or a pair of RAID1s instead of a RAID10 and find a place to move the disks.  Ether inside or a small external enclosure.   The SSDs won't care about vibration.

You want the bays.

2) buy more SAS drives and put them in the SATA bays and migrate to a RAID6.

By doing it this way, native windows will do the TRIM, and there is no overhead for RAID10 or RAID1, and best way to use SSDs.  Don't waste a decent RAID controller on RAID1/10.  All that cache needs to be used on the slower mechanical drives.

This gives you best performance, room to grow.   Use the SSDs for O/S, scratch table space, tmp files, etc .. the put the data files on the RAID6.

Those SSDs won't work properly on the LSI controller .. at least not in error / retry situations. It exposes you for data loss.  They are unacceptable.   They "work" only in the sense that they work until you have some failure scenarios.
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by:dlethe
ID: 39254849
Your current configuration won't even do TRIM.  Going windows software based RAID will give you that, so you will have proper wear leveling and extended life, and no performance hits.
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by:JurajUQU
ID: 39254853
Yes, I've became aware of TRIM just yesterday.

Can you suggest a card that would do it? Are you able to provide a link or pictures to a solution that uses this? I'm having trouble imagining 4 drives outside of the server. As I don't think I'll be able to squeeze them decently inside.
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by:dlethe
ID: 39254864
Do this with native windows host-based RAID1 and a $20 SATA controller.  

The RAID controllers to do support TRIM will generally be limited to a short list of drives and cost thousands of dollars for a high-performance card that won't slow down the SSDs.

Windows Software RAID1 is FAST!  It even does read load balancing, so reads are twice as fast in RAID1 then they would be with a single device.   The problem is that you need expensive RAID controllers to keep up with good SSDs.
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by:JurajUQU
ID: 39254874
I just had a look inside my server - there's room but I need a console or a bracket to mount them so they aren't just 'hanging there'. Power will be also an issue as there isn't any.

I would probably spend more than $20 on a controller but still unsure how to mount it somewhat reasonably. Do you have similar solution implemented, dlethe?
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by:dlethe
ID: 39254894
Well, get a SATA3 controller that is PCIe and can handle the max throughput, and also do a search on the website to see if there are any known issues with that controller and your choice of SSD

As far as mounting SSDs, I've actually used a sophisticated mounting hardware comprised of duct tape to the inside of the enclosure. Like I said, no vibration, so they can touch each other, and they are also non-conductive.  So just find a spot where there is room.

P.S., I've got some SSDs in my home zfs server, sitting on top of the power supply tied together with a pair of rubber bands.  Not even duct tape ;)

I used those extra bays for SAS disks.
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by:JurajUQU
ID: 39254921
hm...if it wasn't that important server I wouldn't particularly mind but it seems as too much mod and introduces risk from another sources.

Might think about Intel or another SSD PCIe card. Bit over budget but def faster and more reliable.

If anyone else has other suggestions, let's hear them.
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by:dlethe
ID: 39254923
Problem with a PCIe card is single point of failure and single point of data loss. Get an external SATA enclosure if you want it pretty, but I though we were going for reliability & availability?
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by:JurajUQU
ID: 39254926
Are you able to post a pic of your setup? I'm really quite curious.

Btw the only space available is right above the power supplies which can certainly get hot so that's why.
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by:dlethe
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Not without shutting down the machine.  This Solaris baby is my NFS; Windows media server repository; primary backup; iTunes; and time Machine server.  I just don't turn it off.  But this power supply inside of it doesn't get hot to the touch so it is a non-issue.

If you are concerned, get a temperature probe for your multimeter and measure temperature at point of contact, and consult the specs on the SSDs.  SSDs are very tolerant to heat.
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JurajUQU earned 0 total points
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OK so I spoke with the guy from a brain institute who are using more than 5PB of data(!) and he told me that I needn't worry about it that he's running similar setup in his datacentre for past few years without any dramas.

I'm setting up OpenManage so I can monitor any changes on the servers and act when something goes wrong.

thanks for help.
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by:JurajUQU
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thanks
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