mlmc

Hello!

Starting of with a "thank you all for a great thread". I haven't read it all yet, but will do! I have a few questions though, maybe someone could help me out. I'll give you the story, hope I won't bore you too much!

I just bought a PERC 5/i (with batt + 512MB ram), it's in the mail and ill receive it on Monday or Tuesday. The reason i bought it was since its cheap and very 'compatible'. I'm planning on installing ESX4.0 on RAID. On the ESX i will run two virtual machines (maybe a third for testing/lab). One of the virtual machines will be a fileserver, the other a windows machine. I'm planning on buying 4x1TB disks, RAID5.

Fileserver: Ubuntu root partition - 15GB, storage partition - 2.8TB.
Windows: W2K3, 30GB system.



I haven't decided what disks to use for the RAID. Reliability, noise, low heat is of most importance, major I/O is not that important. This is where my question marks comes up!

I'm choosing between the following drives:
* WD AV-GP 1TB
* WD Caviar Black 1TB
* WD Caviar Green 1TB


Q: Which one would you chose and why, arguments?
Q: Can i edit the TLER on all of these models?
Q: With a DELL BIOS, can I reconstruct (change from RAID1 -> RAID5) a RAID in BIOS mode, or do I need the OMSA program?
Q: Anyone that can comment on how the PERC 5/i handles in an ESX environment?



I think i'm leaning towards the AV-GP drive, thought I'm not quiet sure. I read some reviews of it, and it does OK.
Any help is appreciated! Thanks in advance..
//M



EDIT: Conclusion regarding purchase of harddisk, se this post.

the_beast

I cannot think of a single good reason why you would want 3 or more disks in RAID0 in a home environment. The sequential transfer numbers will look great, but this will not transfer well into real-world use. The only possible use might be as a work/scratch area for photo or video editing, where fast sequential transfers are required. For OS use though it would be disappointing - even if you wanted a fast area to store your pagefile you would likely get better performance from separate drives.

What would you want to use such a system for?

the_beast

I wouldn't put your OSs on the RAID5 array. I would buy 2 640GB disks (as they are fast & relatively cheap) and RAID1 them. More redundancy and much faster. If you are on a tighter budget consider one of the 250GB or 320GB single platter models.

I may be off the mark, but I understood AV-optimised drives were designed not to stop if an error is detected. So they will not attempt any kind of error correction or re-reads etc. This is what you want when recording video, as a tiny blip in the stream is far more preferable to a skip or stutter while the drive tries to correct a tiny possible error. I would therefore not recommend an AV drive for this purpose - I think they are for set-top recorders etc more than computer use, and the only 2 'AV' disks I have ever seen came in digital TV PVRs. This might be wrong though, I have not researched it further. No idea about TLER on these drives, but I suspect they already have TLER set to a VERY short time limit in light of the above. I would not consider them for a storage array.

TLER can be used on any of the current high-capacity WD drives (or at least I know it can be used on most of them, including the 2TB drives, and I have not heard of any reports of it not working). It can be used on all the 1TB drives I have experience of.

If you do take the OS off the RAID5 array then performance will not be an issue. Take the Green drives and save money on the power bill. It will be touch&go as to whether a 4 drive array will show any real difference in speed between the 2 other disks anyway.

No idea about ESX or the PERC5 bios options - sorry.

Blinky7

I completely aggree, it's that "warm geek-like glow from knowing you are using a better class of hardware" as you say, coupled with the fact that you are different, being the only one with SAS when every other enthusiast goes SSD (and half of them dont even know what SAS is) that attracts me.
That's why I said it's a heart vs mind decission.

In those cases I almost always choose in favour of the mind....and this I will also do this time. However I won't buy the samsung, I will just wait it out to get X25-M like performance at around the 100 euro barrier.

TehQuietAchiever

hey folks, like many others here i am new and joined specifically because of this thread which is clearky the most comprehensive guide to Perc5i's on the web. I bought the card a while back and have read the first 100 or so posts of this thread which has resolved most of my issues thus far. My biggest problem now is cooling. I have decided to go with xboxor's water cooled solution as i already have water cooling in my system. His solution is here:

http://www.overclock.net/hard-drives...d-tips-21.html

I have purchased the same cooling kit he used (Gigabyte Blue Eye) but bugger me if i can work out how he attached it to the loop mounts???

The system i am setting this up for is required for a project so it's quite urgent i get this sussed out. If xboxor or anyone else has had any luck with this please let me know how it's done.

Cheers in advance and thanks once again for an awesome resource

mlmc

That's a great idea, I might do this in the future. But, I need storage space and my economy don't allow 2xSPEEDDISK + 4XSTORAGEDISKS. Ill start with a large RAID5, later on i'll move the OS vmdk files to faster disks..


This is interesting! Maybe the WD-AVs isnt recommended at all for desktop/RAID usage.


OK, noted, thanks!


Thanks for your input! Much appreciated..
//M

the_beast

In that case, I would recommend buying your 4 disks, but only putting 3 of them into RAID5 and using the 4th for storage. Use Ghost or similar to keep an image of your OS drive and you reduce the need for redundancy for your OS drive.

When you start to run out of space on the storage array, buy a new OS disk & set it up using your OS image, then add the extra 1TB back into the array - you can expand the array to use this extra disk.

Or, you could buy 3 1TB disks & 1 OS disk, then add the redundant OS disk and an extra storage drive later.

Or, you could buy 3 1TB drives now & use one for OS and the others RAID1 for storage, then convert to RAID5 later as your needs expand.

Basically, there are lots of options open to you, but I would avoid putting the OS on the RAID5 set as the performance will suffer - RAID5 is not suited to OS use.

Bear in mind that the cost of hardware always drops with time, so you are almost certainly better off buying a system that can grow rather than future-proofing by buying stuff to anticipate your long-term needs. This is especially important if budgets are tight, as you do not want to re-spend money next year if you could have made a more prudent decision now.

mlmc

Why isn't it recommended to run the OS:s on the RAID5? Cause of 'write' latency, but wouldn't this be 'fixed' by the 512MB cache?

Wouldn't it be a benefit to put the OS:s on the (4 disks) RAID5 since the I/O perf would be much greater, an advantage compared to 'one' disk handling two (or possibly three) OS:s?


I've come to a conclusion regarding the disks!
- WD Caviar Green 1TB = Cheap. OK speed. 3yrs warranty.
- WD Caviar Black 1TB = A little more expensive. Performance. 5yrs warranty.
- WD AV-GP 1TB = Same price as 'Black'. Green perf. 1yr warranty.

I'll go with the WD Caviar Black, just because of the 5yr warranty... i guess i could live with the better performance as well..


//M

DuckieHo

SATA and SAS 6Gb/s should be backwards compatible with 3Gb/s controllers.

The stuttering is due to latency issues caused by small writes. It absolutely is a result of the controller. The better controllers have a few MB of cache to buffer these writes. I am not sure if the PERC is "smart enough" for SSDs. I'm not saying it won't help but I'm not sure optimized to fully utilize SSDs.

What's wrong with 3x RAID0 especially with some SSDs? Why would seperated drives be better?

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DJZeratul

I disagree. I have my OS drive sitting on a 5-disk RAID 0 with 2 partitions, one MBR for boot, and another GPT for scratch. Yes, the scratch is mainly for sequential writes. The read speed also adds up to the fact that I can transfer files from the scratch disk to my PERC RAID5 at high speed (sustained real world transfers of 350+MB/sec) which is nice for large uncompressed video files. The OS disk is quite fast as well, with faster boot times and game loading times than 2 WD Raptors in RAID0 on an onboard controller.

I wouldnt go out and specifically buy 5 drives to use in RAID0, that does seem like its a waste. But its certainly not a bad idea if you have the drives already. And Duckie is right, SSDs will actually benefit a lot more from a larger RAID member disk count.

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