Comments on: Virident tachIOn: New player on Flash PCI-E cards market

By: Mitch

Mitch — Sun, 17 Oct 2010 04:23:09 +0000

Joshua: in fact sysbench does not interleave its sequential fileio test, so the test is more of a file locking test than an I/o test, when multiple threads are used. I can point you to the code, if you like.. With a little hacking it can be made to interleave.
Mitch. (from fusion)

By: Joshua

Joshua — Fri, 15 Oct 2010 23:55:04 +0000

The sequential write performance of Fusion-IO is less than 200MB/s? Why so low? The 16KB block size is for both sequential and random tests? And the threads of a sequential test write sequentially to different files in an interleaving manner? It seems to me basically the same as random tests. I guess that is why all the corresponding sequential and random performance are similar to each other. Sometimes the random one is even better than the sequential one.

By: Vadim

Vadim — Fri, 27 Aug 2010 05:28:56 +0000

Tom C,

It is all comes to price for performance question.
If one does not have budget to allow redundancy on servers level then they should go with alternative cheaper solution.

I am not sure what you mean about spikes in writes during week under high load, if you have real data, I’d like to see it.

By: Tom C

Tom C — Fri, 27 Aug 2010 04:49:27 +0000

Unfortunately with both Fusion-io and Virident you still have a single point of failure. If a PCI card fails, even with two PCI-e cards as RAID 1, you will end up with kernel panic or blue screen! Bottom line, sacrificing availability and reliability for simple performance is not an Enterprise solution. Of course you can have multiple servers with multiple cards, but you just doubled your cost! Great for my home PC if it was bootable and was cheaper than my car but not ideal to risk my datacenter! If it is not hot-swappable is not for Enterprise!

Oh yeah, try running these cards for a week under any real write benchmark! Spikes in writes will make you think twice!

By: Vadim

Vadim — Wed, 16 Jun 2010 18:18:38 +0000

Mitch,

As DRAM failures are rare, they still happens. And in this case if you recommend to use RAID0 I think
that would be more correct if you add that RAID0 is recommended to use with proper master-slave configuration.

However there is another catch, as FusionIO allows to handle very high write load, it is quite possible
that slave will not be able to catch-up with master. In my observation as slave is single threaded, slave
is probably able to handle 3x-5x less load than master. And in this case there is good question if
it is worth to setup RAID0 configuration on master if slave not able to catch-up with that performance anyway. It is very workload depended though and topic for additional research.

By: Mitch Crane

Mitch Crane — Wed, 16 Jun 2010 18:11:27 +0000

We’ve typically found controller failures to be about as common as, say, DRAM failures.. that is, after burn-in the probability of such a failure mode is extremely slim. Our manufacturing folks are certainly aware of the need for appropriate burn-in and it’s quite rare that these cases of “infant mortality” go uncaught.

What we find is that people generally implement business continuity (high availability) by using multiple servers and replication for MySQL. There is 1 master and multiple slaves. If one of the slaves goes down, the other slaves keep supporting the business. If the master goes down, then one of the slaves is promoted to be the master. So keeping that in mind, people like to implement RAID 0 because it gives them better performance per server and higher usable capacity. The various technologies we have designed to architect our ioDrive ensure that the card level failure is at minimum.

Regards,
Mitch

By: Vadim

Vadim — Wed, 16 Jun 2010 04:47:19 +0000

Mitch,

Honestly, putting RAID0 is somewhat scary for me. Can’t you have controller failures ?

Also we had FusionIO 320 Duo card failure for one of customers, and card is to be replaced.
Data still can be read, but with RAID0 that means we need to copy whole content to safe location.

By: Mitch Crane

Mitch Crane — Wed, 16 Jun 2010 04:38:02 +0000

Hi Vadim,
Yes, I would absolutely recommend RAID0 on ioDrives (including ioDuo, which will show up as two block devices in Linux). Due to the nature of Flashback protection, our drives effectively (and transparently) maintain a sort of parallelized RAID5 across the NAND devices on a single ioDimm with a dedicated NAND for parity. We can tolerate not only losing (and quarantining) bad blocks, but also losing an entire NAND chip from each bank, with no impact on performance. That’s a very simplified description, but you get the idea. One can be confident striping a duo (or any pair of ioDrives, for that matter) using RAID0.. additionally the stripe will provide approximately linear scaling of bandwidth and IOPS.

In terms of the comparison, it appeared to me from first look at that device that there are multiple, removable NAND modules populated on one PCIe carrier. The question in my mind is how does the device map the PCIe lanes to the controller(s), and on to the chips to provide the stated bandwidth. It is not clear to me whether they will provide multiple bridged connections back across the bus from multiple controllers in a single card, or if it’s just a single controller fronting all of the NAND. In any case, we’re all very excited to see some healthy competition!

Regards,
Mitch (from Fusion-io)

By: Ben

Ben — Wed, 16 Jun 2010 02:35:29 +0000

Happy to see lot of innovation around SSD will see.

By: Vadim

Vadim — Wed, 16 Jun 2010 01:14:15 +0000

Andy,

It was the recommendation from Virident engineers.
size=4096 means to use 4096 block size for XFS filesystem ( instead of default 512), and, as I understand,
this will lead that all IO for Virident card will be aligned, but I can’t say about other vendors.