I've covered SSD interoperability and compatibility issues with HP servers several times here.
Check these posts:
HP D2700 enclosure and SSDs. Will any SSD work?
Are there any SAN vendors that allow third party drives?
So, the move from G6 and G7 HP ProLiants to the Gen8 variants forced a disk carrier form-factor change. HP went to the SmartDrive carrier with the Gen8 product, and that's created a whole set of issues that impact SSD compatibility.
I like the idea of choosing the most appropriate options for my environments and applications, within reason. With G7's, I could use HP's SanDisk/Pliant SAS enterprise SSDs when needed, but also Intel or other low-cost SandForce-based SSDs where it made sense. If using an external enclosure like a D2700 or D2600, I could also use sTec SSDs (which offer another quality SAS SSD option). Drive carriers for the old form-factor were easily obtained.
With Gen8 servers, much of this isn't possible. From the difficult access to the SmartDrive carriers to restrictive firmware and disk validation techniques to the obscenely high price of the HP-branded SSDs ($2500+ per drive), I think HP have priced themselves out of the market.
Their rebranded drives aren't stellar performers, but have tremendous endurance. That's not needed in every environment. Getting the best performance out of HP SSDs on current HP Smart Array controller also requires tuning or even additional HP SmartPath licensing. Previous controllers like the Smart Array P410 were limited by IOPS and other constraints.
A good development that may affect your application on Gen8 servers is the HP SmartCache SSD tiering. Much like LSI's Cachecade, this allows you to add SSD read caching and benefit from lower latencies where it matters. Also see: How effective is LSI CacheCade SSD storage tiering?
In general, I'm not concerned about SSD reliability in RAID setups with disk form-factors. PCIe-based SSDs introduce other concerns. I haven't had any endurance problems, but check: Are SSD drives as reliable as mechanical drives (2013)?
So what can you do?
The D2700 external enclosure may be key here. It uses the older G7 disk carriers. It's also a very solid unit and compatible with old and new generation controllers. You can stuff Intel/sTec/cheapo disks in it all day and be fine. Connect that to the adapter in your hosts, and that will give you the flexibility you require. Use a DL360p instead of a DL380p to save a rack unit.
Intel disks inside of the Gen8 server... I wouldn't do it, if for any reason than to avoid the POST 1709
errors. Plus you'll be self-supporting in a way that impacts the main server unit. I just had a customer try to fill a 25-bay DL380p Gen8 with Intel SSDs and eBay drive carriers. He had to return the Intel drives and use low-end HP SATA disks for the system to even work.
The HP ProLiant DL380p Gen8 is offered in 8-bay, 12-bay15, 16-bay and 25-bay units.
The 8-bay has been fine. It's a good platform, especially if you add external storage.
The 16-bay Gen8 has no SAS expander card (and is incompatible with the excellent HP SAS Expander), so you need two internal RAID controllers to use it. As a result, your logical drives cannot span the two 8-bay drive cages. This is a departure from the G7s, where 16-bays/disks in one array was no problem.
The 25-bay unit has a concerning design flaw. The SAS expander is embedded on the 25-drive backplane. This backplane requires a P420i controller with FBWC cache to function. Fine. I had three RAID controller DIMMs die in a 60-day period, though. On the 8-bay units, this just disables write cache. On the 25-bay server, a cache failure makes the Smart Array a "zero-memory" controller and disables all access to the disks!! Avoid this model unless you can accept that risk. My failure rate on 2GB cache modules is far higher than 1GB modules, so I downgrade to the 1GB modules for this specific platform.
1746-Slot z Drive Array - Unsupported Storage Connection Detected -
SAS connection via expander is not supported on this controller model.
Access to all storage has been disabled.
As far as "support" goes, you'll be hard pressed to find this spelled out in the documentation. Most 10th-generation and newer Dell servers have good documentation available with a list of all of the supported drive models, but I've not seen this for the 2950. I can tell you from personal experience that the 2950 never introduced SSD support of any kind. With that being said, it may still work since communication is through a SATA interface. You run the exact same risk as with using any other non-Dell-certified drives, in that there may be problems with a specific model or drive FW that never gets addressed if it's non-certified (hardware and firmware validation testing are only carried out w/ Dell-branded drives). In the end, unless you can find an instance of someone having documented a test with the exact hardware combination as you (same server, controller, and SSD model), you're just not going to be able to know without testing it out.
In regards to comments on controller performance... The PERC controller itself can often become a bottleneck when using SSDs, especially when you get into older (ancient) cards like the PERC 5/i, and even newer cards if your I/O footprint is write heavy & random, e.g. a database of some kind. Go with the newest card your system is compatible with (PERC 6/i) if it's an option for you.
Another note on performance - LSI controllers (rebranded as PERC w/ Dell) don't currently support SSD TRIM like typical (newer) desktop integrated RAID controllers do. Long story short, that means that you're going to see very poor write performance after a bit of use unless you use a model w/ built-in garbage collection (e.g. SSDs with Sandforce controllers, like those made by Intel).
Best Answer
SSD Drive: OCZ Vertex EX 60 GB SATA II 2.5 Inch SSD
By all accounts it is the most popular/best reviewed single-level cell SSD drive available for 'Enterprise' applications. Their literature claims for the 60GB model:
There is a really excellent benchmark and review here.
HDD Drive: Western Digital Blue Caviar 80GB SATA II 7200 RPM Drive
This is a typical drive we'd find in our systems. Literature claims:
The test machine is a Dell SC1425, 2x3.6GHz Xeons, 16GB of RAM.
Created fileio test data thus (data on both HDD and SSD drives):
sysbench --test=fileio --max-time=60 --max-requests=1000000 --file-num=10 --file-extra-flags=direct --file-fsync-freq=0 --file-total-size=50G prepare
Created mysql test data thus (data on both HDD and SSD drives):
sysbench --test=oltp --db-driver=mysql --mysql-socket=/tmp/mysql.sock --mysql-db=test --mysql-table-engine=innodb prepare
Note: a 2.5" in a 3.5" adapter chassis (makes 2.5" drive fit in 3.5" slot) will not work with Dell 3.5" drive sled as connector alignment is off. Assume you will need a 2.5" back plane when using these SSDs, we'll probably use the R610.
Note: I tested zfs, xfs and ext4 too, as well as two SSDs in a software RAID0... but there is no room to post them here and for the most part a single ext3 SSD performed best. I'll do more tests, but it didn't seem to like software raid.