Cache was not a factor due to dataset size (a copy of 50GB). The speed of the whole operation was equvalent to reading from the Raptor, and a copy from the first RAID5 array to the second array gave better performance than reading from the Raptor and writeing on the array.Oh yes, so he did, my bad. Very interesting this is then! So how could you tell the Raptor was the bottleneck? And did you take into any controller cache? I'm quite interested in this.
As you write he has a 3 disk RAID5 array. I don't dispute that a 3 disk RAID5 is slower than a 2 disk RAID0. Always will be, because in reality there are only data distributed over 2 disks in the RAID5 and there are parity to be calculated and written. A 5 disk array with a good controller shall beat RAID0, if correctly configured.I have serious doubts whether a 5 disk RAID 5 system will beat two disk RAID 0 for write performance. For pete's sake it's all on the original post. This guy has 2 disks in RAID 0 and it was lightning fast and then had 3 disk RAID 5 and it was dog slow. Same hardware, different setup, and it's slower, that's what you'll get with any controller.
Ah, I think I might know why that's the case now. Whilst I was browsing through the source material I read that sequential writes can give reasonable performance on a RAID5 system but its random writes that are the problem. So this would make sense.Cache was not a factor due to dataset size (a copy of 50GB). The speed of the whole operation was equvalent to reading from the Raptor, and a copy from the first RAID5 array to the second array gave better performance than reading from the Raptor and writeing on the array.Both arrays consists of 5 500GB 7200rpm SATA harddisks. Can't remember make or model of his controller.
On the same controller RAID 5 with a larger number of disks may beat RAID 0 with a smaller number of disks, e.g. 5 disk RAID 5 over 2 disk RAID 0 (which I still think is disputable but I don't think we'll ever agree on that one) but 5 disk RAID 5 will always lose to 5 disk RAID 0.A 5 disk array with a good controller shall beat RAID0, if correctly configured.
Hmm, well it's most likely a controller configuration or quality issue. If the file system basically works but it is just slow then the basic RAID system is working so either there's some funky settings on the RAID controller or it's just naff.Anyways there are certainly something terribly wrong with his configuration. If it takes seconds to read ID3 tags from MP3 files in WinAmp, something has gone horribly wrong. The best advice is to reformat and experiment with different parameters, until performance is acceptable - but with 3 disks he won't reach RAID0 levels, and without a dedicated controller, writespeeds won't be optimal.
This is true but my original already-off-topic point wasn't focussed on using databases, I was just using it to demonstrate what I was saying about RAID 5 write performance being bad. At the end of the day, you should never implement RAID 5 if you are focussed on performance, only if you want a large reliable and cost-effective filesystem.If you are a heavy Oracle user (with those expensive licenses), with databases which aren't that big, but accessed intensively, then money won't be a problem. If money is no problem, a massive RAID 1+0 with 15k SAS or fibrechannel disks will certainly outperform RAID 5 with a similar number of disks (but sacrificing capasity). But here we are talking a very special situation, and even here it will difficult to recommend the added expense if money has any importance at all.
Exactly - RAID 0 is a questionable idea with two discs, but as it goes from questionable to bad, and on to atrocious when adding more disks.Not that I'd ever ever recommend 5 disk RAID 0. 8O
Only in very special cases, have you only got one focus. Small highend Oracle databases where money is no object is one such case.This is true but my original already-off-topic point wasn't focussed on using databases, I was just using it to demonstrate what I was saying about RAID 5 write performance being bad. At the end of the day, you should never implement RAID 5 if you are focussed on performance, only if you want a large reliable and cost-effective filesystem.
Don't put words into my mouth. RAID 0 with 2 disks is a very good idea on a performance oriented system. RAID 0 with more disks is a very good idea on a specialised performance system.Exactly - RAID 0 is a questionable idea with two discs, but as it goes from questionable to bad, and on to atrocious when adding more disks.
- On filesystems where the focus is performance RAID 0 beats RAID 5.Only in very special cases, have you only got one focus. Small highend Oracle databases where money is no object is one such case.
Well from enterprise level experience I disagree! RAID 5 is not considered anything more than adequate for performance and should never be the focus for getting a RAID 5 system put into place. RAID 5 is a good system and is very widely used in the industry as it is a good "general purpose" solution. The irony is that I mainly use RAID 5 filesystems at work, even on some database servers, but that's because performance isn't an issue.Generally RAID5 performs very well (not best) across a lot of usage scenarios, and starting with a good controller and 5 disks, it is also very performarnce/cost efficient. I am always balancing the requirements when making recommendations, and except for outlaying cases (very small systems or highend databases) RAID5 gives a lot of performance and capasity for the money. And it should certainly always beat single drives......
Well if you don't care much about your data, or you are very good doing backups to DAT, LTO or external harddisk, then you should let the 36GB SCSI drive be system drive (no RAID) and the two WD drives be RAID0.I have one 36GB SCA SCSI with a host adapter and two Western Digital Caviar 16MB 250GB. What is the IDEAL setup for performance on these 3 drives? I want pure, no punches pulled, screaming perdformance. (With what I have)
Yes.So I should install the OS on the SCSI and everything else on the two SATAs?
Thats another yes. And when your SATA RAID0 goes poooff, then you can still boot your system. You can even experiment to your hearts content with different RAID stripe sizes, block sizes and other parameters, as you don't need to reinstall your OS every time.And even if the SCSI is not included in the stripe, I can still boot from it and use the SATAs right?
Depends. The 680i is not the best RAID, but then again, it's not that bad. And RAID0 is NOT very taxing from a controller point of view, so you should be ok with the onboard solution.And would a PCI-e SATA RAID card be faster than onbaord SATA RAID? (eVGA T1 680i LGA775)
Nice little hardware collection 8)Well I have a 6 port PCi-E SATA RAID Controller. I also have a few more SCSIs. I have 2 15k SCSIs and 2 host adapters. What Should I do? How should I use the 2nd one? Paging file? I have 2gb of RAM so i turned paging off.
Well I'd recommend you use the 36Gb disk purely for backup, but if you aren't bothered about that I honestly don't know what would give better performance. The SCSI disk would like give better random access times, meaning accessing lots of small files would be quicker, but the RAID 0 array will give better throughput, meaning accessing large files would be quicker.So I should install the OS on the SCSI and everything else on the two SATAs?
Yes, this should definitely still be possible!And even if the SCSI is not included in the stripe, I can still boot from it and use the SATAs right?
I don't know. Intel's ICH RAID is fairly mature these days but some other onboard controllers aren't quite as good. Plus it depends one the quality of the PCI-e card. Your best bet is to try and find some benchmarks and look at performance and overhead because most onboard and I suspect some add-on RAID controllers are partially software based.And would a PCI-e SATA RAID card be faster than onbaord SATA RAID? (eVGA T1 680i LGA775)
SCSI beats anything not RAID, and SCSI RAID beats SATA RAID. Any 15k SCSI harddisk beats the Raptors, no contest.Would a SCSI with a host adapter be better for gaming?
SCSI would be nice, SAS is much better (Serial Attached SCSI).Would a SCSI with a host adapter be better for gaming?
I can and it wwould be close to free =) I work with them and we get lot's of outdated but still good parts =). So 74G SAS and a nice controller SAS/SATA x10 might end up in trash any time....Yeah, but name someone who can afford a SAS drive and a controller card...
GOOD $HIT MAN! Better guard those cans... I am getting my SCSIs from work. Anyone wanna buy some? Free for me.