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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

SSD RAIDS...

J

Jeff Brown

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Looking for peoples experience with 2.5" SSD Raids.

Looking at 4 or 8 in a RAID 5 via something like an Atto R680.

Hearing mixed things about Raid 5 and SSD.

Interested in what enclosures / SSD drives have been successful as well as speeds etc.

Any thoughts appreciated!
 
I would highly recommend Maxx Digital RAIDS if your going SSD you can look at SAS or Thunderbolt options from them.
Haven't had one fail me. I would look into the Thunder RAID.

http://www.maxxdigital.com/thunderraid-380.html



Also look at some of the higher bandwidth SSD like the new Sandisk,Muchkin and OCZ Vertex 4.
 
You don't want to put SSD non-enterprise drives in anything other than a RAID 0, they wear out very quickly because the drives are constantly overwriting themselves trying to match up parity in a RAID 5/6 and they only have a single I/O since they're SATA. If you want to use an HBA RAID controller such as ATTO/ARECA/3WARE then your best results will be from using SAS drives or enterprise SATA drives.

Any RAID over Thunderbolt will be limited to around 500 MB/s, but the data is both UP/DOWN steam simultaneously, so even 4-8 enterprise SATA 7200 rpm drives in a RAID 5/6 will hit that data rate ceiling.
 
Shiblon Wixom said:
You don't want to put SSD non-enterprise drives in anything other than a RAID 0, they wear out very quickly because the drives are constantly overwriting themselves trying to match up parity in a RAID 5/6 and they only have a single I/O since they're SATA. If you want to use an HBA RAID controller such as ATTO/ARECA/3WARE then your best results will be from using SAS drives or enterprise SATA drives.

Any RAID over Thunderbolt will be limited to around 500 MB/s, but the data is both UP/DOWN steam simultaneously, so even 4-8 enterprise SATA 7200 rpm drives in a RAID 5/6 will hit that data rate ceiling.
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Exactly. But, if you are looking for pure speed for playback (4K DPX for example) SSDs have a low point of failure and you can get awesome speeds in RAID zero with very few drives. Then copy the media over mini-SAS or TB to a raid 5 sata raid for more protection. TB raids are great if you are transcoding from media on the drive and writing proxies back to same volume - but I almost never do that.
 
Thanks guys - useful.

This would be for small / portable but fast use as a Scratch Raid (ie a very fast copy for QC and dailies rendering) Checksummed copies would go to different slower but safer media. I'm thnking 4-8TB to cover 1-2 days rushes and then delete and repeat.

Does anyone know if there is a compatibility chart out there for Atto Raid cards ad various SSD drives - can't seem to find anything certified?
 
Jeff Brown said:
Thanks guys - useful.

This would be for small / portable but fast use as a Scratch Raid (ie a very fast copy for QC and dailies rendering) Checksummed copies would go to different slower but safer media. I'm thnking 4-8TB to cover 1-2 days rushes and then delete and repeat.

Does anyone know if there is a compatibility chart out there for Atto Raid cards ad various SSD drives - can't seem to find anything certified?
Click to expand...

Perfect example of a good use of RAID 0 SSD raid.

You should use Samsung 840 Pro 256GB or Corsair Neutron GTX 256GB - I like the Samsung best. Here's a review that features both - http://www.maximumpc.com/article/hardware/best_ssd
 
Jeff Brown said:
Thanks Mark some good tips - now I just need to work out the size / weight / noise / heat implications.......
Click to expand...

Cheetah ST3600057SS is very quiet. SSD will always be silent and lighter than spinning disks - but ... for 4T+ you need 16 256Gs SSDs as opposed to 7 600G SAS drives. 7 of those Cheetah's in a RAID zero will be insane. Even at RAID 5 it will mostly likely be faster than you need.
 
Over thunderbolt you won't see more than around 500 MB/s (bi-directional, 1GB/s aggregate), so a small portable SSD raid0 is great for 1-2 days worth of materials, just make two copies, though a single 1TB SSD might work better.

just make sure to securely wipe/format the drive between projects, SSD are always faster when they don't have to over-write previous cells/blocks of data.
 
Save your money. Unless the RAID supports the TRIM command (I'm not aware of any at this moment), performance will start to degrade very quickly.

If you're planning to use a single RAID controller, say an 8 port with 4 used for HD and 4 for SSD RAID, forget it. You'll probably need a 2nd RAID controller just for your SSD array.

I tried this and sharing the cache RAM on the RAID controller with two arrays slowed my original hard drive array down massively.

I disconnected the SSD array and gave up.

Hopefully in another year or so some RAID cards with TRIM support will come out.

You might be able to use a software ARRAY (from your motherboard), if it supports TRIM when used as RAID.

This IBM pdf on pitfalls of SSD RAID was interesting. http://www.research.ibm.com/haifa/conferences/systor2011/present/session5_talk2_systor2011.pdf
 
Jeff Brown said:
Thanks Les very useful.

When you say degrade do you mean performance / speed degrade or do you mean the SSDs physically degrade, as in get worn out?
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Performance.

Without garbage collection (which runs in the background), being able to mark freed up space as zero'd out, when it has to write it will have to do an erase and then a write, which is very, very slow.

Unless you can provide TRIM, there's no way for garbage collection to happen.

Formatting the array (writing zero's) in a RAID along with the stripe, is the Opposite of how you actually format an SSD. SSD's are in put in a virgin state by writing 1's, not 0's.

So, when you are 'initializing' the SSD drive in the RAID, you are actually writing data, that will need to be erased and written over in normal operations.

It was very frustrating for me to learn all this. I called tech support at LSI first before I bought the SSD's, and they said that even though they didn't support TRIM, the RAID BIOS was aware that they were SSD drives and would handle it.

They gave me incorrect information.

In the future, they may offer TRIM and I expect they will be one of the firsts that do. I've always had good results with LSI/3ware drives.

But, don't let some vendor lead you down a path. Without TRIM, it's just not going to work how your want, and there may be other "gotcha's" like the one I discovered where adding an SSD array to my existing card that already had an array, slowed down my main array. Ahhhh!
 
Consumer SSD drives are fine in RAID 0, they usually have a lower rate of failure, but drastically lose performance and durability in a RAID5/6, can't maintain parity across the drives. LSI/3ware controllers typically work well with enterprise SLC drives and not so well with consumer MLC or TLC drives.

SLC SSD drives are designed for write performance, like the LSI warp drives, and are more expensive.
 
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Shiblon Wixom said:
Consumer SSD drives are fine in RAID 0, they usually have a lower rate of failure, but drastically lose performance and durability in a RAID5/6, can't maintain parity across the drives. LSI/3ware controllers typically work well with enterprise SLC drives and not so well with consumer MLC or TLC drives.

SLC SSD drives are designed for write performance, like the LSI warp drives, and are more expensive.
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Without TRIM, at some point when using and SSD, you'll have to do an 'erase and then a write' which will slow you down - unless there are SLC drives that write at the same speed no matter what data (1 or 0) is previously stored in the cell?

But, yes - SLC drives are much better drives, far more reliable, etc. Wish the RED SSD's were SLC.
 
They tend to be used for write intensive applications, they do wear out faster than MLC. And a 300 GB SLC is several times the cost of a similar sized MLC drive. Not sure I'd pay $4500 for a 256 GB SLC drive.
 
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At Maxx Digital we have been doing a bit of R&D on SSD RAIDs... I just want to say SSDs are tricky.

Every time an SSD has something written to it, it shortens the life of the drive, in general, because the NAND cells have a limited amount of write cycles.


TRIM is something the SSD manufacturers came up with to extend the life of the drive...it works by the OS sending a TRIM command every time a file is deleted, directly to the drive controller, so the drive controller knows which cells have been written to the most and it knows where the spare cells are. The problem though is that they never came up with a solution for TRIM to work behind a RAID controller. TRIM will not work behind any true hardware RAID controller, as it requires that the OS have direct access to the drive, not a virtualized group of drives that are striped together behind a RAID controller. There is no way to pass the TRIM data to the individual drives behind a hardware RAID controller.


On our 6Gb RAID products, when someone creates an SSD raid group, we also provide the ability to overprovision right at the RAID card level; which basically means we will cut the amount of useable space of the SSD raid group down by whatever amount you prefer to extend the life of the drives. But when you are using drives that are already overprovisioned, it isn't really necessary to overprovision them again at the RAID group level. So basically, the solution to the problem of lack of TRIM on SSDs has pretty much been decided by the industry as two things working in combination - garbage collection on drive controller firmware, and over provisioning on drive controller firmware and / or on hardware RAID controller firmware.


Regardless of what you do, the write performance of an SSD or SSD raid group will diminish over time, no matter what.
 
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