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SSD drive instead of HP SAS drives

engfelt
Occasional Advisor

SSD drive instead of HP SAS drives

Anyone runs HP Proliant servers with SSD drives? I am thinking of running 6x160GB Intel SSD drives instead of 6x146GB SAS drives in a HP Proliant ML330 G6. Any pros/cons?
Thanks
Niklas
2 REPLIES
Tamás Csillag
Occasional Advisor

Re: SSD drive instead of HP SAS drives

HP started to supply SSD drives themselves, so it should be okay to use them.

Pros would be improved (practically no delay) seek time, which is great for database and email servers (and any Windows server).

Cons: might be drive wear if your application writes a lot, so don't expect more than 3 years. It may live much longer, just don't count on it. Also long, sequential reads might be slower than on a 10kRPM SAS drive.

Just my 2 cents...

Cheers,
Tamas
Almantas Klimas
Occasional Visitor

Re: SSD drive instead of HP SAS drives

I run them and will share my experience below.

 

As HP customer I was very satisfied to find that Smart Array P410, P411 controllers properly support them - HP is competing on quality, and not creating pitfalls for non-HP product.  Very good, I now like this company more than before.  Choice is yours. Of course there is no support for cross device integration - for example, there is no automatic non-HP SSD firmware upgrades from P410 controller, so when Intel will release new firmare you will need to take them out, one by one, and upgrade individually inserting into laptop. HP drives can be upgraded in place, 100 drives at a time...

 

The Smart Array management application correctly shows "SSD drive" as a description with P410, 411 controllers.

 

Do not try to use older controllers like P800 or P400 - they are simply too slow and the whole new P410 cost like one SSD drive - you probably installing SSD to get more speed. 2-3 SSD drives will saturate P400 or P800 controller, and they only run SATA at 1.5Gbps - that is too slow. You need a controller that supports SATA at 3Gbps (SAS at 6Gbps).

 

Beware - Intel X25M 160GB SSDs are made from MLC flash and have ONLY 30TB total write limit.  If you write 30TB they are gone. No matter to which sector or partition - the wear is distributed by controller, so total writes to disk is what counts. Before replacing ordinary drives with SSD open diagnostic report in Smart Array application and find write counters for the physical drives (HP drives have them).. Check how many bytes were written to each drive, and if you know how long drives were working for specific application you can estimate how long SSD will work until weared out - take 20TB as fail safe limit.

 

Otherwise, if you need more writes, you need to buy X (extreme) series of Intel SSD, they are made from different SLC flash and have 2PB (petabyte) write limit per 64GB drive. To be on safe side, buy orginal HP SSD drives, then you do not need to care about writes, use them as ordinary drives with no practical limits.

 

I would suggest to use max. 8 drives per P410. Buy another Smart Array for additional drives, do not use SAS extenders. Never use RAID5 with SSD if there are many small writes.

 

SSDs do fail also (I had two failures in one year), just about 5 to 10 times less often as mechanical drives, in my observation. We will yet see what happens when they will become older.

 

The question is when the TRIM command pass-through will be implemented, so that it works through P410 controller to the SSD drives, for example. Before that is implemented, maybe a better idea could be a SATA multi-port add-in card that has one port per SATA SSD drive and AHCI driver will pass TRIM directly to drives.  Probably performance will be better than with Smart Arrays. Just a quess.

 

But for those who need more speed there is even better solution - avoid SAS or SATA protocol translations entirely. Buy SSDs that attach directly to PCIe bus. Perfomance will be at least 10 times faster, if not 100 times... there are both MLC and SLC models, depending on planned write intensity:

 

http://h18000.www1.hp.com/products/quickspecs/13587_na/13587_na.html

 

It may seem quite costly, 300GB cards cost about $7000 at the time of this post, but such a card gives perfomance like a disk array with some 400 drives, and more market players appearing (LSI, RamSan, etc.) so cost will probably go down soon to be not too far from the cost of flash packed as SATA drives.

 

The last advice - make sure you really need the I/Os, and if your application will utilize the SSD disk performance.  For many applications with Smart Array Flash backed 1Gbps cache you can achieve similar application performance, with no care about write limits and with less cost than using SSDs...