To RAID or not to RAID?

[Gurm]

That is the question.

I have hard drives three. The first two are identical. I also have a RAID controller. It is spiffy. I am tempted to make a striped array for maximum performance.

HOWEVER - currently the three hard drives contain (among other things):

1. System Files
2. Swap File
3. Scratch Space (Photoshop) and Streaming Space (CD burning).

Question - is the speed increase of the RAIDed array enough to offset the performance lost by putting the swap file back on my system drive?

- Gurm

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Listen up, you primitive screwheads! See this? This is my BOOMSTICK! Etc. etc.

[Jorden]

Reading the 2 identical drives, I wonder what the 3rd is. You seem to be going for a stripe 5 array, which needs a minimum of 3 HDD's, right?

Then your 3rd HDD needs to be the same size as the other 2. (Hardware RAID 5)

If you only plan on RAIDing 2 drives, you should put the swap file back on the non-RAIDed disk, AFAIK.

Most servers I work with using RAID 5 don't use a swap file. They have over 1 Gb of RAM.
But I'll sure ask at work next Monday

Jord.

[xortam]

RAID performance will be limited by the weakest of the drives. Ideally, you want to use identical drives or drives with the same performance metrics (rotational speed, seek time, size). If you have two 20 GB drives and one 10 GB drive, then only 10 GB will be utilized across each of the drives. What RAID level are you looking to implement? RAID 0 (which really isn't RAID at all) is the fastest and highest capacity but has no fault tolerance. Post your RAID controller and drive specs as well as desired RAID level, installed RAM and OS.

P.S. Also, remember that you'll need to reformat if you ever want to add/subtract drives from the RAID array.

[This message has been edited by xortam (edited 08 December 2000).]

[cjolley]

Raid of course!
Use Ghost to move things around.
chuck

PS What would posses you to put your swap file any where but the array?


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ABit BE6-2 V2, P3-650@923, 256mb@142cas3, 90gig (2x45) IBM 75GXP striped raid array, SB Live Value@3.0, Pioneer 104s DVD, Mitsumi CDRW@2x2x8, Acatel 1000 ADSL@1.5mb/sec, Linksys EtherFast NIC, LG 995e, USB mouse,Matrox G400 MAX!!!!

[This message has been edited by cjolley (edited 09 December 2000).]

[Greebe]

cjolley,

What would posses you to put your swap file any where but the array?

PS. Video editing

[Gurm]

Ok, sorry I wasn't specific enough.

It's a FastTrak-100 EIDE RAID.

It's Raid 0, I'm not interested in mirroring or data integrity, just performance.

It's two identical IBM U100, 7200rpm drives (same lot and batch) and a non-identical WD drive (also U100,7200rpm).

As for the swap file, it is ALWAYS better to have it on a drive differing from your system drive or the drive you intend to spool from/to if it's possible. Reasons include video editing, fast cd-burning (12x, for example), etc.

Also Photoshop 6 is VERY SLOW if you can't put its scratch file on a different drive from the swap file.

Let me know, ok?

- Gurm

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Listen up, you primitive screwheads! See this? This is my BOOMSTICK! Etc. etc.

[cjolley]

Gurm,
How much memory do you have?
chuck

[Jorden]

Be even more specific, Jason: Hardware or Sotware striping? Plus yes, as Chuck asks, how much memory do you have?

You're not interested in mirroring or data-integrity? So we can cross off Level 1 to 5, leaving you at Level 0: Disk Striping?

"Disk Striping does not provide any fault tolerance because there is no data redundancy. If any partition in the disk array fails. all data is lost"

... You mean that kind of RAID?

Jord.

[Gurm]

512mb pc150

hardware

yes, raid0

- Gurm

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Listen up, you primitive screwheads! See this? This is my BOOMSTICK! Etc. etc.

[cjolley]

Gurm,
With 512 megs of ram I wouldn't worry to much about separating your system files from your swap file. Your performance hit is probably going to be mostly theoretical.
A single drive has no fault tolerance either. The risk to your data will go up slightly depending on the statistical variance of the drives MTBF. This won't be much.
chuck

[Gurm]

Ok, to be even more specific, here's the hardware I'm looking at (this is for work, and maybe if I like it I'll duplicate it at home):

MSI motherboard with Fasttrack-100 Lite (Lite=Built-In and only does 0, 1, and 0+1).

Two IBM 7200RPM U100 45GB drives (brand new).
One WD 40GB 7200RPM U100 (also brand new).

The way I have it now, system files are on IBM #1, Swap is on IBM #2, and Scratch/Spool is on the WD. If I raid the two IBM's, swap would move back onto the first "volume"... while scratch/spool would remain on the WD.

So is the consensus I'm hearing to do it (I'll do regular backups, of course, noting the increased risk of array failure)?

And, is it really twice as fast? Or is it more like 50% faster?

- Gurm

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Listen up, you primitive screwheads! See this? This is my BOOMSTICK! Etc. etc.

[cjolley]

If you deal with a lot of large files it is realy fast!
Leave the stripe size at the default 64k.
You will like it.
chuck

[cjolley]

Benchmark update:
Norton show the same for single & raid. They are either not realy benching or benching the engineering cylinder of just one drive.
Sandra shows more than twice as fast.



chuck


[This message has been edited by cjolley (edited 09 December 2000).]

[This message has been edited by cjolley (edited 09 December 2000).]

[Greebe]

Jason, with the tests I've done on these, I find that there is ~70% improvement over standard IDE drives alone.

cjolley, I won't use Sandra to prove anything related to system proformance, I have it for comparative results of others finding when using it.

[xortam]

Gurm ... throw them all into the array unless the WD has significantly slower seek times than the IBM drives (remember performance is throttled by the slowest drive which includes seek time). It doesn't matter which volume you place your files into because the data is interleaved across all drives in the array. You'll get a little performance kick by using three drives versus two for RAID 0: Second drive is the big kicker, every additional drive after that helps some. You won't be using much if any swap file with 512MB RAM so that's not an issue. The ap spooling drive will benefit from the increased RAID performance which will counter the benefit of placing it on a dedicated drive and controller. You would have to benchmark your ap under a typical system workload under both configurations (all RAID vs. IBM RAID and WD stand-alone) to really determine which is better but it probably isn't worth the effort. Having all three drives on RAID would generally benefit your entire system. To really tweak your system, you would also need to investigate which stripe size is appropriate. Smaller stripe sizes are appropriate for system and application files while larger stripe sizes are appropriate for large streaming files: You may need to pick something in between depending on your needs.