Combining SSD and HDD in HP dl380p?

Question

I´m planning to buy a dl380p with 25 sff slots with 2 ssd:s raid 1 and 10 hdd:s raid 5, having room for 13 more hdd:s in the future.

Is this possible or do I need two raid cards?

Solution 1

Firstly - great choice, we have lots of that exact model - you know you get the dual-port 10Gbps 533FLR-T NIC adapter with that model too!

Anyway, with the 25-slot model you get a P420i controller with 2GB of memory and that supports the full 25 internal disks inside that machine just fine. Now one other thing to consider is potentially using the SSD/SSDs using HP's SmartCache - this uses the SSD to sit in front of the hard disk based array and acts as a read-cache for all the disks. We use it and love it, right now it doesn't do write-caching but we're beta-testing a future version that does do this and is likely to be released in time for G9 and will be a free upgrade. The HP P/N: for SmartCache is D7S26A btw.

Solution 2

You don't need an additional RAID controller to do what you're asking.

You can combine SSDs and spinning disks on the same controller and backplane. They cannot be mixed in the same logical drive, though.

I took note of the SSD you're planning to use; 691862-B21. It's a pretty low-end drive. How do you intend to use the SSD drives?

The 25-bay server works okay, but relies heavily on an internal SAS expander (which allows the use of one RAID controller), but also cannot function without the cache module. The stock 2Gb RAID cache experienced a ridiculous amount of failures in my environments, so I swap them out for 1Gb cache modules. If cache fails on this server model, you lose access to all disks.

That's the only warning about this model.

The SSDs you spec'd aren't particularly fast throughput-wise, but may be an improvement for random read performance. HP markets that particular SSD as a read-optimized disk. It's write performance is very poor (easily surpassed by regular disks). If you can give a better idea of what you need the SSDs for, I can make a better configuration recommendation.

Comments

[pepoluan]

Not sure what your needs are, but if IOPS is a top priority for you, check out Fusion-IO's ioDrive products.

[Chopper3]

What aspect of it needs to be quick? the reason I ask is that memory is pretty cheap right now and nothing will speed up your server like a good chunk of memory. If you're doing a lot of writing then a R1 array of even the cheapest SSDs will make a huge difference, if it's all reads then you need to understand what the nature of those reads are, i.e. is it from a fairly small set of random data across your whole storage or a known chunk of data that's read often? if you can get a better understanding of that then that'll guide you better, and we have help more too :)

[Pontus]

We bought a dl360p, the fastest one, with 8 1.2Tb 10K sas disks. Its a lamp server, replacing a mac mini server. After installing it all I was really surprised that the mini rendered the website slower than the mini. I did some tests and they where all faster on the hp server, but when rendering the page and checking with microtime() it was allways faster on the mac. I relised that it was about the ssd, so we bought a D2700 for the disks and ssd:s for the server and now its alot faster. The framework (kohana) uses alot of file exists and I think thats what makes the difference.

[ewwhite]

@pontus Which SSD?

[Pontus]

The database isn´t even a gigabyte and the server has 64 gb ram. I was expecting things to be cached in ram, but it didn´t change over time. The mac renders a normal page under 100ms, and the d360p was sometimes up at 250ms on the same page before changing to ssd. We are now buing a new server for our other system and feel like doing it right the first time this time...

[Pontus]

@ewwhite This one: h30094.www3.hp.com/… two in raid 1.

[ewwhite]

@pontus Your issues with performance aren't hardware related. Can you tell us what operating system you're using?

[Pontus]

@ewwhite Its Ubuntu server 12.04 with default php/mysql with no changes at all.

[ewwhite]

@pontus See my answer. This is probably OS and system tuning related. Likely scheduler, etc.

[Pontus]

Would you expect 10 10K 1.2tb sas disks raid 5 be faster than 2 ssd raid 1 in a mini? I´m happy with the rendering times after changing to the ssd:s, we dont have many writes, we hardly have traffic, but the traffic we get should get quick renders. We will probably never write to the same block twice since we hardly delete.

[Pontus]

What ssd would you recommend? Do you have a serial number for that 1Gb cache?

[ewwhite]

@pontus You can probably just use the SSDs you initially spec'd. But at this point, you need to perform the benchmarking. I don't know anything about your data set size, application or any specifics.