RAID Array Stripe Alignment affect Performance Tags: NAS / RAID Performance Storage klau1 November 2, 2012 5:53:05 AM Just found out that RAID arrays can have alignment issues, separate from the well known 4K sector issue. I suspect it to be the cause of slow transfer rates on my Adaptec RAID 3805 RAID6 (5x Hitachi 2TB 7200 RPM) array. Nodesoft Disk Bench only gets 100MB/s writes and 80MB/s reads (these figures are more in line my Windows File Copy performance) http://www.nodesoft.com/diskbench But I don't know why the following benchmarks report so much higher Atto/HDtach: Crystal: However, I think I have confirmed that my array is not aligned, but am not sure. State of Array: Results: Alignment Calculator: http://www.techpowerup.com/articles/other/157 Alignment Checking Script: http://www.ocztechnologyforum.com/forum/showthread.php?57599-RAID-Non-RAID-Partition-Alignment-for-max-performance&p=518021&viewfull=1#post518021 Quote:Device ID: Disk #2, Partition #0 ======================================================= Total Volume Size: 5 TB Starting Offset: 134235136 (131089 KB) Partition Alignment: ** NOT ALIGNED!! ** VM Check Alignment Tool: http://ctxadmtools.musumeci.com.ar/VMCheckAlign/VMCheckAlignment10.html My Calculation: Formula: ((Partition offset) * (Disk sector size)) / (Stripe unit size) Source: http://support.microsoft.com/kb/929491 Partition off set = 134235136b Disk sector size = 512b stripe unit size = 262144b block size = 512b answer = 262178 This is an integer, thus indicates the array is aligned. But this conflicts with the conclusions of the other calculators, so WTF? I have no idea what I'm doing lol :weep: Array Info: Adaptec RAID 3805 RAID6 HD 5x (Hitachi 2TB) Sector Size: 512Bytes Stripe Size: 256K Disk Format: GPT Windows Disc mode, Basic or Dynamic: Basic More about : raid array stripe alignment affect performance Can't find your answer ? Ask ! Publish Related resources : ForumPerformance scaling with SSDs in raid array ForumCan you add a SATA drive in an existing SAS Raid -0 array ForumStripe size ForumIntel RST RAID performance . ForumSetting up RAID array ForumICH10R RAID Slower than Single Drive ForumSeveral RAID 0 arrays, stripe sizes? ForumAdding an external RAID array ForumSlower than expected performance with RAID / SSD Array ForumHelp me with my Adaptec RAID 5 array please! ForumRAID stripe size performance ForumDoes RAID 1 actually increase read speed? ForumWhat Raid 0 STRIPE SIZE should I choose? ForumSSD raid and Trim question ForumBest SSD Of 2013, Which is it? ForumSSD's and RAID 0 (noob) ForumSSD's, RAID, and boot drives. ForumTwo ssd + hdd for best performance? ForumRAID 1 broke but HDs OK ForumIs their a difference in gaming performance with 6gbs/3gbs More resources Read discussions in other Storage categories Hard Drives DVD Drives DVD Writers Optical Media Flash Media NAS/RAID SSD Western Digital !