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Issues with low speed in a specific RAID setup

Issues with low speed in a specific RAID setup

J
JustAKoala_
Junior Member
11
05-28-2022, 03:50 PM
#1
I operate a Dell R720 as a NAS alongside other low-power applications. Within this case, I have three distinct RAID configurations, each unique in its characteristics. Two function perfectly without any problems, irrespective of access patterns. The array under discussion raises concerns because it comprises six 7.2k RPM 2TB Toshiba drives arranged in RAID6 on a PERC H710 mini. The write cache is configured to use the cache when a stable power source is available; read cache adopts adaptive ahead mode, though forcing this didn’t enhance performance. The array remains healthy, with one global hotspare available but not currently utilized. When accessing the SMB share initially, response times are satisfactory, though slightly inconsistent. Reading or bulk writing causes network latency and eventually crashes on Linux clients. On Windows systems, speeds drop dramatically—sometimes to just 1 MB/s—while benchmarking in Windows Server with CrystalDiskMark shows read speeds between 10MB/s and 50MB/s, and write speeds of 90MB/s to 200MB/s. By comparison, a RAID5 setup with three 4TB disks consistently delivers 200MB/s reads and 70-90MB/s writes. Another RAID-1 array is dedicated to Hyper-V VMs; although its performance is modest (~100MB/s reads, ~70MB/s writes), it matches expectations for four 5400RPM drives. My curiosity lies in why one array lags so much. Might the block size be set at 64k while using a 4k allocation unit? I recall achieving 700-800MB/s over SMB without issues, though general slowness has persisted. The hardware itself hasn’t changed since then. Could it be that the drives in this array aren’t Dell-certified or lack PERC support? The other drives do support PERC and show no similar issues. iDRAC logs indicate only normal RAID controller activity. Additional details: PSU is redundant 750W, functioning properly; UPS provides sufficient backup power; CPU and RAM specifications are adequate; operating system is Windows Server 2022; all three arrays use NTFS.
J
JustAKoala_
05-28-2022, 03:50 PM #1

I operate a Dell R720 as a NAS alongside other low-power applications. Within this case, I have three distinct RAID configurations, each unique in its characteristics. Two function perfectly without any problems, irrespective of access patterns. The array under discussion raises concerns because it comprises six 7.2k RPM 2TB Toshiba drives arranged in RAID6 on a PERC H710 mini. The write cache is configured to use the cache when a stable power source is available; read cache adopts adaptive ahead mode, though forcing this didn’t enhance performance. The array remains healthy, with one global hotspare available but not currently utilized. When accessing the SMB share initially, response times are satisfactory, though slightly inconsistent. Reading or bulk writing causes network latency and eventually crashes on Linux clients. On Windows systems, speeds drop dramatically—sometimes to just 1 MB/s—while benchmarking in Windows Server with CrystalDiskMark shows read speeds between 10MB/s and 50MB/s, and write speeds of 90MB/s to 200MB/s. By comparison, a RAID5 setup with three 4TB disks consistently delivers 200MB/s reads and 70-90MB/s writes. Another RAID-1 array is dedicated to Hyper-V VMs; although its performance is modest (~100MB/s reads, ~70MB/s writes), it matches expectations for four 5400RPM drives. My curiosity lies in why one array lags so much. Might the block size be set at 64k while using a 4k allocation unit? I recall achieving 700-800MB/s over SMB without issues, though general slowness has persisted. The hardware itself hasn’t changed since then. Could it be that the drives in this array aren’t Dell-certified or lack PERC support? The other drives do support PERC and show no similar issues. iDRAC logs indicate only normal RAID controller activity. Additional details: PSU is redundant 750W, functioning properly; UPS provides sufficient backup power; CPU and RAM specifications are adequate; operating system is Windows Server 2022; all three arrays use NTFS.