Storage Advisors Comments

Comment on Real-life RAID reliability by: Tom

Thu, 01 Nov 2007 17:24:32 +0000

Oops. Link is fixed. Sorry about that.

And here it is again just so you don’t have to scroll back to find it.

Enjoy!
TT

Comment on SAS drive performance by: Vic

Thu, 01 Nov 2007 12:12:27 +0000

I would have made the same decision between the 6 and 8 drives as to the maximum sustained output being bottle necked by the rest of the subsytem. But you are forgetting performance when the load is not at the maximum of a the total system like when in a database you are performing a series of transactions which are not running in parallel but are sequential. You are not reaching anywhere near the capacity of the system. What you have essentialy are small data requests and the 50% speed advantage in seek time and latency of each 15K drive makes the difference. The difference is though you can still support the same number of users in both setups but your 12 hour nightly job will take only 9 hours with the 15K drives.

Comment on Write-back cache: Battery vs Disk by: SJS

Mon, 29 Oct 2007 21:46:21 +0000

Why not implement this storage on something like Compact Flash that will survive a power outage?

Comment on Picking the right stripe size by: Skip

Sat, 27 Oct 2007 15:17:44 +0000

WOW! You guys are awesome….

I have a Sun SE610 and a Sun ST5320 (NAS Gateway). We will be setting up the SE6130 to serve disks to the NAS gateway and then provide NFS export/CIFS shares to all the users. The CIFS shares will primarily be used for home directories and office size files (30K-800k) and the NFS shares will primarily be accessed by Unix systems with 1M-1G files. My plan is:

The SE6130 has 2 controllers (1 controller tray with 10 146GB FC drives and an expansion tray with 10 146GB FC drives (20 drives total).

My Plan (Please feel free to chastise me, as I am not married to it)
I will create 4 RAID-5 vdisks (each 4+1) with a stripe size of 512k
On each vdisk I will create five equally sized “volumes” (~100GB each). I will assign each volume in alternating sequence to a controller allowing access to the ST5320 (which is direct fibre attached). For example vdisk1vol1 will be assigned to controller A and vdisk1vol2 wil be assigned to controller B. I will do this until all 20 ~100GB volumes are assigned to the ST5320. (The assignment to a controller is somewhat arbitrary as both controllers have access to all volumes, but use the assignment as priority (I think)).

From the ST5320 I will create my initial “base volume” for each export/share starting with a different vdisk for each share. For example share 1 will use vdisk1vol1, share2 will use vdisk2vol1, share3 will use vdisk3vol1, and share4 will use vdisk4vol1, share5 will start again at vdisk1vol2, etc…. I will continue this until I have all of the shares created (about 12 shares)

Obviously not all shares are going to be the same size. The way the 5320 works, as I understand it, is the base volume is shared, then I grow that base volume(share/export) by simply adding LUNS as extents to the share. This is done on the fly without interruption to the end users accessing the shares. As each share/export needs additional space I will simply add space using the same “round-robin” fashion as I created them.

Sorry so long… My question is what do you think? very simple.

Comment on RAID Stripe width by: maobo

Tue, 16 Oct 2007 00:17:30 +0000

I want to ask a question about the read/write cache size ratio in the real storage controller. As we know the write cache is usually a battery-backed RAM in storage controller. But for battery life limit, its size are restrict to a small size. What the really ratio in the common storage controller? Thank you very much.