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Advice on our SAN

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Matt Wright
Advice on our SAN
on Jan 16, 2009 at 2:22:17 pm

Hi There, I am a bit of a newbie to the world of SAN's. so please be gentle

Anyway here is what I am trying to do, we have 3 video editors who are using a SAN. we predominantly use Sony Vegas, and deal mostly with mxf 35mb/s files or Decklink Uncompressed files all in HD.

We have a Xyratex 5402E Raid Enclosure loaded with 12 x 500GB SATA Drives, the enclosure has 2 Fiber Channel Controllers, which in turn are both connected to a QLogic 4GB Switch. and then we have 3 XP64 computers connected via FC to the Qlogic switch at 4GB.

The 12 drives are configured currently as 2 banks of RAID 5, so we have 6 drives Raided together as a Raid 5, and the other 6 also raided together as a Raid 5.

Then in windows XP we Raid 0 the 2 partitions back together to create a single shared resource. We are using MetaSAN software on the 3 systems to access the drives giving us file level sharing.

So my problem, It just seems really slow, I can manage get a maximum Read / Write of about 225MB/s Read and 150MB/s Write, which isn't too bad I guess, but I would expect it to be a bit quicker, and also we get pauses and inconsistency's with the data rate. The data rate will just plummet down to about 20MB/s Read and Write for a second then fire back upto full speed, which to be honest is crap if you are trying to edit HD streams.

I think the problem is basically down to Block Size settings in the Raid Configuration, Cache Settings in the Raid software, sector size settings in Windows, and also which Raid partition is accessible through which Fiber Controller on the Xyratex COntroller. and unfortunately this has so may variables I am not sure where to start to try and improve the situation.

So my question to SAN Masters, is HELP !!!!, well, lets say do you have any advice to get my speeds up and more consistent.

Many Thanks for this

Matt


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Bob Zelin
Re: Advice on our SAN
on Jan 18, 2009 at 1:02:12 am

I don't know your product, but you should not have created 2 volumes with 6 drives each. You will have limited speed with only 6 drives. Again, I don't know your product (your array), but modern arrays (like the Cal Digit HDElement) are doing 250Mb/sec with only 4 drives in RAID 5 configuration, but older arrays like the Apple XServe RAID would only get 220Mb/sec with 14 drives (these were PATA, not SATA).

Want more speed - reconfigure with all 12 drives as one volume.

Bob Zelin




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Matt Wright
Re: Advice on our SAN
on Jan 19, 2009 at 10:00:09 am

Thanks Bob

Can I check a couple more things with you, you seem to be the man with the knowledge.

Originally we set the raid up as 2 Raid's and we had a 32bit system accessing the drive, which wouldn't access the logical drives over 2TB, I think we can get around that now, as most of the systems are 64bit, so would I could set one large drive. WOuld I need to format this as GPT or could I still format a drive of around 5TB as NTFS. WHich wuld you recommend ?

If I did this, would I be able to share this volume over to a 32bit system, or would it only be 64 systems which could even see it, and is there any software to get over this issue.

So if I rebuilt this as a single raid, I would share the raid over both controllers, is there any standard Cache, block setting that I should aim for in building the raid suitable for editing purposes. Unfortunatle I have a little knowledge and this is perhaps my downfall, a little knowledge is a scary thing.

Many Many Thanks

It would be great to get all this hardware working a little better

Matt



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Bob Zelin
Re: Advice on our SAN
on Jan 20, 2009 at 3:24:56 am

I am not the man with the knowlege. I am very weak at SAN systems, but it seems that I am the only guy willing to answer. On Win XP systems, I partition the large arrays into 2TB volumes - this is no big deal, and works well with single 8TB volumes. Windows Disk Manager does this for you (with your input). With a hardware Raid controller (like Areca - again, I don't know your hardware), you can create volumes in the bios, before you even get into Windows.

bob Zelin




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Sean ONeil
Re: Advice on our SAN
on Jan 20, 2009 at 7:54:33 pm

[Matt Wright] "The data rate will just plummet down to about 20MB/s Read and Write for a second then fire back upto full speed, which to be honest is crap if you are trying to edit HD streams."

I've seen this problem a lot with various equipment. Don't have an answer for you though. Try a large RAID-0 to see if it goes away. The RAID controller might not be powerful enough to write RAID-5 fast enough. If that doesn't help, contact Xyratex.

GPT is not a file-system. It's a partition table. You can still create an NTFS disk with a GPT and have a volume greater than 2TB. But your Xyratex machine has to support this in order for it to work.

Sean


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