CEP2 and HDD speed.

[fallwind]

I also posted this on the WCG forums but I know not everyone goes there, so here it is:



Just thought I'd post some results from a couple of my rigs running CEP2. The pic above shows BOINC's elapsed time on the left and BOINCviews CPU time on the right. The upper data set is from a 980x at 3.8GHz with BOINC installed on a traditional 7200RPM hard drive. The second data set is from a 980x at 4.5GHz with BOINC installed on an 40GB OCZ Vertex 2 SSD. The BOINC numbers look funny because I stretched the image a bit to get everything to line up better.

As you can see, the SSD equipped rig only loses 5-6 minutes per task for an efficiency of around 99%. The HDD rig is losing 35-50 minutes per task, for an efficiency of about 90%.

On a side note, it's only been a couple days, but so far I haven't had any problems running 100% CEP2's on the 3 machines I have dedicated to the project.

[Gamekiller]

There's also a thread there about running it Ramdisk style. https://secure.worldcommunitygrid.or...d_thread,30244

I think it's kind of the same, right?

[fallwind]

Yeah, pretty much. If you can swing it, a RAMdisk is the way to go since it's practically free and even faster than an SSD. The problem is the BOINC folders on my machine are currently over 7GB with a 1 day work buffer, CEP2 takes up alot of room...lol! You'd need a ton of RAM to fit that(plus a couple GB of free space) into a RAMdisk. It may be a more practical solution on a quad core with no HT and a minimal work buffer. But then again, I bet a regular HD could easily handle the I/O from 4 threads of CEP2.

[Metroid]

My case, 8 work CEP2 units use 6 to 8GB of pagefile, 6 to 10GB of SSD and 1 to 2GB of ram. I never saw anything like. To run this properly with a RAMdisk would need 24GB of ram.

[haschioz]

so what exactly does this tell us? a ssd is better for crunching? and the times clockspeed wise dont add up...your 3.8ghz machine is faster than it should be, maybe post a couple days of runtime and post them again with a similar clocked machine hdd vs ssd to compare.

[shoota]

yeah i'm confused by this. i was under the impression that hard drives don't affect output

[Snow Crash]

The efficiency issue is specific to running multiple CEP2 WUs at the same time ... CEP2 is I/O intensive.
Due to this, WCG by default limits 1 CEP2 in your que at a time.
You will only be effected by the aggregate I/O inefficiency if you went to your device profile and at the very bottom of the page told it to ignore the WCG limits.

I *think* this effect is limited to the Windows world ... they had released for Linux a long time ago.

[EtaCarinae]

As you can see, the SSD equipped rig only loses 5-6 minutes per task for an efficiency of around 99%. The HDD rig is losing 35-50 minutes per task, for an efficiency of about 90%.

Excellent news. I will put to test with CEP2 my new rig I am building which will have a Crucial 300 SSD (Sata 3). When you run 12 cores things add up and in absolute numbers 10% of a high number remains a high number.

[trn]

Good findings, CEP2 WU's hammer the HD's. Probably the best way to run the project is mixed with other normal WU's vs running 8 or 12 CEP2 WU's at once.

[fallwind]

Yes, I posted this thread as sort of a warning to XS crunchers. CEP2 has alot of HD activity and with the number of people running 980x's and SR2's here this information needs to be known. In the past you could run any old crappy HD on a beast of a rig and it would crunch just fine. That's not the case with CEP2. A mechanical drive can only handle about 4 concurrent CEP work units before you start losing CPU efficiency. Once you get to 8 or 12 of these runing at the same time, you lose alot of efficiency and risk OS crashes and WU errors.

Speaking of errors, the rig in the OP with the mechanical HD starting throwing "Task exited with zero status but no finished file - Restarting" errors today. I'll limit CEP2 to 4-5 threads till the SSD I ordered for it shows up next week.

so what exactly does this tell us? a ssd is better for crunching? and the times clockspeed wise dont add up...your 3.8ghz machine is faster than it should be, maybe post a couple days of runtime and post them again with a similar clocked machine hdd vs ssd to compare.

SSD's are better for this particular project (CEP2). With all the others, HD speed doesn't make any difference.

Also, CEP2 work units are variable length so completion time is not and idicator of CPU speed.

[Nikolasz]

I think boinc needs to be rewritten.
Too much hdd usage. Ramdisk is ok, is fast as memory speed......

I got single tasks takes 10gb of hdd usage, i only got 4gb fast memory other two comps that crunch 24/7 got 2 gb memory

[D_A]

It's not BOINC it's the science application that has the issue, but CEP2 does have particularly high HDD usage for some reason.

Fallwind, correct me if I'm wrong, but I though excessive writes was particularly bad for SSDs. I'm not claiming to be an expert here, that was just my understanding.

[jcool]

Fallwind, correct me if I'm wrong, but I though excessive writes was particularly bad for SSDs. I'm not claiming to be an expert here, that was just my understanding.

They are. For most (MLC-based) SSD anyway...
Thanks for the info. I was gonna try CEP2 on my SR-2 rig soon. Time for the SSD Raid (2x Vertex LE's) to show what it's made of

[Metroid]

SSD host writes before the CEP2 project 1.2T, after 5 days 8 work units 3.3T.

Pagefile is disabled so it uses the ram, now imagine if the pagefile was also enabled on the SSD

[fallwind]

It's not BOINC it's the science application that has the issue, but CEP2 does have particularly high HDD usage for some reason.

Fallwind, correct me if I'm wrong, but I though excessive writes was particularly bad for SSDs. I'm not claiming to be an expert here, that was just my understanding.

You're absolutely correct. I have no clue what the effect could be on SSD life while crunching this project long term. That's why I'm equipping 3 rigs with small cheap SSD's just to contain the BOINC folders and I'll dedicate them to this project for the forseeable future. If an SSD dies, that's what the warranty is for....lol!

[D_A]

Since I have the sum total of ONE HDD that I bought new, I tend to get pretty good value out of them, but that also means I end up using a lot of older, slower drives. Of course if I kill one in a dedicated machine, who gives a rat's ass!

[Rob_B]

I'll limit CEP2 to 4-5 threads till the SSD I ordered for it shows up next week.

Is there an option to limit that? Or do I just select other projects too and hope they get mixed up nicely?

[Nikolasz]

It's not BOINC it's the science application that has the issue, but CEP2 does have particularly high HDD usage for some reason.

Fallwind, correct me if I'm wrong, but I though excessive writes was particularly bad for SSDs. I'm not claiming to be an expert here, that was just my understanding.

Totaly agree.

[fallwind]

Is there an option to limit that? Or do I just select other projects too and hope they get mixed up nicely?

You can limit a machine to 2 CEP2 work units at a time total (in queue and/or in progress). You can find the option for this in your WCG device profiles. Other than that, there is no way to control how many come through other than manually suspending and resuming tasks as needed.

[SMTB1963]

It's not BOINC it's the science application that has the issue, but CEP2 does have particularly high HDD usage for some reason.

Fallwind, correct me if I'm wrong, but I though excessive writes was particularly bad for SSDs. I'm not claiming to be an expert here, that was just my understanding.

So WCG applications are not bound by the "Task checkpoint to disk" setting in the BOINC software? This would explain why I was seeing constant write activity to a machine I had devoted to CEP, no matter what I set the checkpoint value to. I would also explain why it fried my USB drive so quickly.

This document from Toshiba says:

To even begin to reach a conservative endurance limit of a 64GB MLC NAND-based SSD with wear-leveling technology, a mobile user would have to write approximately 40 Terabytes (forty trillion bytes) of data over the expected five-year life of the drive. That’s equal to approximately 22GB of new data per day, every day – or enough to fill 4.6 DVDs, or 32 CDs daily. With a 128GB drive, for example, the wear would be spread over a larger storage area, effectively doubling the average daily write limit to 44GB, or more than 9 DVDs.

Anybody have any idea what the write load per thread per day might be for CEP?

[EtaCarinae]

On the mechanical HDD side I am running now CEP2 on 12 threads per machine on four machines Sata2. They have fast 10'000 rpm 150 and 300 GB Raptors. I run it also on one 8 core machine but that has a more slow 500 GB WD disk. In a few days 'l see how these rigs will behave. And later I am eager to compare with my new SSD rig.

[Metroid]

My case since day 1 is 50~70% = 100%. So it does not take 10~12 hours to be completed. It takes around 6~8 hours. Is anyone similar to my case?

[fallwind]

Metroid, yes that is normal. The work unit will progress to around 60% and then suddenly jump to 100% completion. There is an explanation for this behavior on WCG forums but I can't recall the reasoning.

==================

Just another FYI. I have also experienced OS crashing when the OS and BOINC are installed on the same SSD. This has happened both with Win 7 and Server 2003. If I put BOINC on the SSD all by itself and leave the OS on a mechanical HD or another SSD, everything is fine. This never happened with Ubuntu but Windows seems to have problems with extended, heavy disk useage.

[EtaCarinae]

I have returned now a little over a hundred valid WUs. The Elapsed time per WU varies from 3.5 to 10 hours with all values in between. The majority is around 7-8 hours. These are running on 980X CPUs with HT at 3.7 and 4.0 Ghz with fast ram and disks.

[Metroid]

Metroid, yes that is normal. The work unit will progress to around 60% and then suddenly jump to 100% completion. There is an explanation for this behavior on WCG forums but I can't recall the reasoning.

Thanks

Just another FYI. I have also experienced OS crashing when the OS and BOINC are installed on the same SSD. This has happened both with Win 7 and Server 2003. If I put BOINC on the SSD all by itself and leave the OS on a mechanical HD or another SSD, everything is fine. This never happened with Ubuntu but Windows seems to have problems with extended, heavy disk useage.

Strange, both my OS and BOINC shares the same SSD and I had no issues. I'm using Intel. Are you using Intel or Sandforce?