SSDs in a DSS200?

[Leo Enticknap]

Has anyone tried to use SSDs in a DSS200 RAID?

I have a customer with a DSS200 manufactured in 2010. It's in use in a high end residence theater, left on 24/7, but only used for 1-2 screenings a week typically. It still has the factory-installed 500 GB 3.5" drives, all of which have a significant number of reallocated sectors. For continued reliability, they need to be swapped out.

There is no need to increase the RAID capacity: this server simply doesn't have enough content passing through it for that to be an issue. So upgrading to 1TB spinning rust drives (about the smallest you can buy nowadays) wouldn't make any sense. I'm therefore wondering about replacing the existing drives with these 500 GB SSDs. The lifetime of a traditional drive is measured in power-up hours, whereas of an SSD, the number of write cycles is the main determinant. It therefore seems to me that a drive that will be powered up 24/7, but writing only for around two hours a week, is a good use case for an SSD. Furthermore, if, as I suspect, that server only lasts another 2-3 years, the drives will be reusable in other equipment.

My question is this: if I put these drives in a typical 2.5" to 3.5" adapter, and then into the DSS200 RAID cartridges, will the combined SATA/power connector line up in the right position to plug into the backplane? I've only used these adapters before for drives that will be connected using a cable, not directly onto a board. If anyone knows of a specific model of adapter that will work, I'd be grateful for suggestions.

[Marco Giustini]

I feel they’ll work but I’m concerned whether the old kernel supports the trim feature which is important for ssd’s

[Mark Gulbrandsen]

Keep in mind that it's the write cycles that kill SSD memory, not the read cycles. I am not sure the Dolby is not constantly writing some sort of data back to those drives that might put wear and tear on the memory, because the OS also lives there. I would seriously consult with Dolby before you do it. I actually find it odd that no one has recommended SSD's for their servers yet. USL was the only one that did that. I would be curious to see what Harold has to say about using them.

[Frank Cox]

Trim is a method of wear levelling that re-allocates space otherwise used by deleted files. On a drive that's used only for reading and very little writing (like this apparently is) the need for using trim would be very infrequent.

If the server doesn't support trim natively it would probably be adequate to just deal with it when doing regular maintenance visits because, again, the need would be very infrequent. Rip 'em out, hook 'em up to a computer, run the trim, then put them back. Just another maintenance chore to add to the list for that site.

[Harold Hallikainen]

My involvement in the USL CMS was pretty limited. It was designed with SSDs from the very start. The low power consumption made more power available for other parts of the system. Read speed was very good. Reliability appeared good, but not enough systems ended up in the field to get good data. The CMS-5000 used very small form factor SSDs which saved a lot of board space.

Harold

[Mark Gulbrandsen]

Trim is a method of wear leveling that re-allocates space otherwise used by deleted files. On a drive that's used only for reading and very little writing (like this apparently is) the need for using trim would be very infrequent.

If the server doesn't support trim natively it would probably be adequate to just deal with it when doing regular maintenance visits because, again, the need would be very infrequent. Rip 'em out, hook 'em up to a computer, run the trim, then put them back. Just another maintenance chore to add to the list for that site.

I have had two SSD's develop problems and one failure resulted in my loss of Quick Books. Luckily, backups saved the day there. There are also different types of SSD memory used, some do not become affected by lots of repeated write cycles like most do, But those SSD are generally very expensive, IT grade drives.

Here is some insight into the different types of memory used in them...

"SLC, MLC, and TLC NAND


These three memory types are the primary kinds of NAND chips seen in modern SSDs. The most common in the early days of consumer SSDs were MLC (multi-level cell) and SLC (single-level cell). MLC was generally the cheaper of the two. The "multi-level" of MLC refers to the ability of each MLC memory cell, in most cases, to host four states and thus two bits per cell due to its architecture. (SLC memory cells can exist in only two states, 1 and 0, and thus store one bit per cell.)

SLC in general is stabler over longer periods but also more expensive. MLC's higher densities make it cheaper to manufacture (you get more chips out of a given wafer), but error compensation in the firmware is necessary to keep it in check. MLC also tends to be rated for fewer read/write cycles than SLC. A variant of MLC, enterprise MLC (eMLC), uses technologies that forestall cell wear and thus data loss, and premium-price drives based on these "stabler" drives are marketed for business or high-access environments."

[Leo Enticknap]

These WD SSDs (link in original post) are marketed as being specifically for NAS use, so I'd hope that they have wear leveling firmware to take account of that.

Thanks folks. Need to try an adapter with a 3.5" drive in a DSS or DSL somewhere, to confirm that it aligns with the backplane OK.

[Steve Guttag]

I actually find it odd that no one has recommended SSD's for their servers yet. USL was the only one that did that.

Doremi/Dolby has been doing that for IMS servers that support 2TB drives. So has Barco's Alchemy.

[Carsten Kurz]

I have seen both adapters that mounted the SSD in the middle of a 3.5" drive space, or on one side so that the connectors match a 3.5" drive. I bought one for my HP workstation so that I can mount an SSD in it's OEM slide-in bay.

I would just try it. The DSS200 so far have been very forgiving with various non-recommended drives. Probably because it's the RAID card that deals with the actual drives, and the DSS itself only sees the volumes.

[Leo Enticknap]

Thanks. If alignment is an issue, the nuclear option would be to mount the drives somewhere else in the case (e.g. by Velcro to the base of the chassis), and take the SATA breakout cable from the RAID card straight into them. Need to wait until we get a DSS in the shop to experiment with.

[Mark Gulbrandsen]

Something like this ought to work Leo... And they are really cheap.

[Steve Guttag]

When putting the drives in a caddy, like is done on most servers, there is more than getting the width right. The SATA connector has to line up because the caddy does not, typically adapt the SATA/Power connections. An adapter that merely centers the 2.5" drive in 3.5" won't have the connector in the right place. It's fine for a typical Mini-Tower computer since those hook up via cables, not caddies.

[Mark Gulbrandsen]

When putting the drives in a caddy, like is done on most servers, there is more than getting the width right. The SATA connector has to line up because the caddy does not, typically adapt the SATA/Power connections. An adapter that merely centers the 2.5" drive in 3.5" won't have the connector in the right place. It's fine for a typical Mini-Tower computer since those hook up via cables, not caddies.

They also make offset adapters just for that reason.

[Steve Guttag]

I don't doubt it but the graphic of your post showed a "centered" drive adapter...which I've used on my work desktop...no issues with that.

[Leo Enticknap]

I eventually did a spot of jerry rigging. The unused cartridges in slots 5 to 8 have plastic trays in them in place of 3.5" drives. I drilled holes in them to align with the screw holes on the underside of the SSD (using a 1:1 scan of it, printed out, as a template), mounted the drives in the cartridges with countersunk screws, then hooked them to the connectors on the backplane with these cables. The server is working well so far.