Comments on: Observing weirdness … http://storageadvisors.adaptec.com/2009/01/22/observing-weirdness/ Storage Solutions for Real World IT Professionals Sat, 20 Mar 2010 05:54:58 +0000 http://wordpress.org/?v=1.5.2 Comment on Observing weirdness … by: Neil http://storageadvisors.adaptec.com/2009/01/22/observing-weirdness/#comment-309069 Mon, 09 Feb 2009 04:55:46 +0000 http://storageadvisors.adaptec.com/2009/01/22/observing-weirdness/#comment-309069 HS, Glad to be of assistance. Good luck. Neil HS,

Glad to be of assistance.
Good luck.

Neil

]]> Comment on Observing weirdness … by: HS http://storageadvisors.adaptec.com/2009/01/22/observing-weirdness/#comment-307329 Fri, 06 Feb 2009 17:48:28 +0000 http://storageadvisors.adaptec.com/2009/01/22/observing-weirdness/#comment-307329 Thanks for your input Neil. We actually found some nice JBODs from Area Data Systems. We'll be doing some IOP testing in a few days time with them. I think they're certified with the Adaptec 5085 controller with the redundant path failover capability. Thanks again Neil. Thanks for your input Neil. We actually found some nice JBODs from Area Data Systems. We’ll be doing some IOP testing in a few days time with them. I think they’re certified with the Adaptec 5085 controller with the redundant path failover capability.

Thanks again Neil.

]]> Comment on Observing weirdness … by: Neil http://storageadvisors.adaptec.com/2009/01/22/observing-weirdness/#comment-304592 Tue, 03 Feb 2009 04:49:16 +0000 http://storageadvisors.adaptec.com/2009/01/22/observing-weirdness/#comment-304592 HS ... 24 drives in a hotswap chassis is not what I'd call "direct attach", but that's only terminology. That's basically what I'd call a "dumb" backplane (no expander). As for performance of non-expander vs expander backplanes ... two-tenths of five-eighths of ... (so small you would never notice it). Thanks Neil HS …

24 drives in a hotswap chassis is not what I’d call “direct attach”, but that’s only terminology. That’s basically what I’d call a “dumb” backplane (no expander).

As for performance of non-expander vs expander backplanes … two-tenths of five-eighths of … (so small you would never notice it).

Thanks
Neil

]]> Comment on Observing weirdness … by: HS http://storageadvisors.adaptec.com/2009/01/22/observing-weirdness/#comment-302761 Sat, 31 Jan 2009 15:02:08 +0000 http://storageadvisors.adaptec.com/2009/01/22/observing-weirdness/#comment-302761 Thanks for the reply Neil. My apologies but I should've mentioned that our 24 direct connect is actually 24 drives in hotswap bays on the chassis so we wont have to play with cables or power down anything. Is there any performance hits in using SAS expanders? Thanks for the reply Neil. My apologies but I should’ve mentioned that our 24 direct connect is actually 24 drives in hotswap bays on the chassis so we wont have to play with cables or power down anything. Is there any performance hits in using SAS expanders?

]]> Comment on Observing weirdness … by: Neil http://storageadvisors.adaptec.com/2009/01/22/observing-weirdness/#comment-300641 Wed, 28 Jan 2009 03:59:52 +0000 http://storageadvisors.adaptec.com/2009/01/22/observing-weirdness/#comment-300641 HS ... I seriously need to read the manual for this software ... somehow I keep getting the answers out of order ... damn. However, regarding your questions about direct-connecting 24 drives to a raid card ... There are two kinds of backplanes ... smart (expander) and dumb (no-expander). If you don't like expander backplanes (which I'll come to later), then use a non-expander backplane, but either way, for 24 drives use a backplane. Reason why? If you direct-attach 24 drives, then when a drive dies you have timing problems. Let's say a drive dies at 10am on Monday morning. Hopefully you have a hot spare and it kicks in, but you can't shut the system down to physically replace the drive until later that night. This means you are running for a longer period of time than optimal without the hotspare etc etc. Another issue is that you have to shut the system down to change the drive, which is a pain in the neck in many circumstances. The most important problem here, believe it or not, is the fiddling around with cables and power connectors. Adaptec Tech Support see a heck of a lot of cases where people say "a data cable was accidentally disconnected" ... with 24 drives thats 24 cables and a whole chunk of complication. If the drives are in a JBOD of some description (internal, external, smart or dumb), then it's just a case of unplugging the drive, replacing with a new drive and rebuilding the array etc. It's a whole lot cleaner, and causes a whole lot less pain in the long run. Now if you are having problems with backplane implementations ... look at Adaptec's implementation guides which we've done up on various jbods to simplify this matter and clear the confusion for people. They can be found on our website in the Resource Centre. Thanks Neil HS … I seriously need to read the manual for this software … somehow I keep getting the answers out of order … damn.

However, regarding your questions about direct-connecting 24 drives to a raid card …

There are two kinds of backplanes … smart (expander) and dumb (no-expander). If you don’t like expander backplanes (which I’ll come to later), then use a non-expander backplane, but either way, for 24 drives use a backplane.

Reason why? If you direct-attach 24 drives, then when a drive dies you have timing problems. Let’s say a drive dies at 10am on Monday morning. Hopefully you have a hot spare and it kicks in, but you can’t shut the system down to physically replace the drive until later that night. This means you are running for a longer period of time than optimal without the hotspare etc etc.

Another issue is that you have to shut the system down to change the drive, which is a pain in the neck in many circumstances.

The most important problem here, believe it or not, is the fiddling around with cables and power connectors. Adaptec Tech Support see a heck of a lot of cases where people say “a data cable was accidentally disconnected” … with 24 drives thats 24 cables and a whole chunk of complication. If the drives are in a JBOD of some description (internal, external, smart or dumb), then it’s just a case of unplugging the drive, replacing with a new drive and rebuilding the array etc.

It’s a whole lot cleaner, and causes a whole lot less pain in the long run.
Now if you are having problems with backplane implementations … look at Adaptec’s implementation guides which we’ve done up on various jbods to simplify this matter and clear the confusion for people.

They can be found on our website in the Resource Centre.
Thanks
Neil

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