RAID Controllers — 40 Frequently Asked Questions
Real questions enterprise IT engineers ask about RAID Controllers, with practical answers from Pro Disk Engineering. Questions sourced from Server Fault and Network Engineering Stack Exchange under CC BY-SA — see source links per question. Answers are original Pro Disk Network content with links to our buying guides and product catalog.
What are the different widely used RAID levels and when should I consider them?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (194 votes · 50,324 views) ›
Why is RAID not a backup?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (131 votes · 68,853 views) ›
Software vs hardware RAID performance and cache usage
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (88 votes · 123,027 views) ›
How to interrupt software raid resync?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
Array rebuild planning: RAID 6 rebuild on 12-drive 4TB array typically takes 24-48 hours. Schedule monthly consistency checks (mdadm --action=check on Linux) to catch latent errors before they trigger a rebuild.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (60 votes · 160,919 views) ›
Is it possible to reboot a Linux OS without rebooting the hardware?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (97 votes · 47,040 views) ›
How to monitor the hard disk status behind Dell PERC H710 Raid Controller with CentOS 6?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
SMART monitoring: alert on attributes 187 (reported uncorrectable errors), 197 (current pending sector count), and 198 (offline uncorrectable count). Non-zero values typically indicate 30-90 days of remaining service life.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
Interface selection: NVMe (PCIe Gen4/5) for random workloads above 500 IOPS. SAS SSDs for mid-tier. SATA HDDs for capacity / backup tiers. Match drive interface to RAID controller; mismatches force fallback to lowest common denominator.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (31 votes · 172,415 views) ›
Is it better practice to buy RAID disks individually vs. in bulk?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (99 votes · 13,532 views) ›
What is better LVM on RAID or RAID on LVM?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (61 votes · 89,279 views) ›
What is the current state (2016) of SSDs in RAID?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
Interface selection: NVMe (PCIe Gen4/5) for random workloads above 500 IOPS. SAS SSDs for mid-tier. SATA HDDs for capacity / backup tiers. Match drive interface to RAID controller; mismatches force fallback to lowest common denominator.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (54 votes · 49,652 views) ›
RAID - software vs. hardware
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (55 votes · 12,868 views) ›
Is bit rot on hard drives a real problem? What can be done about it?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
Interface selection: NVMe (PCIe Gen4/5) for random workloads above 500 IOPS. SAS SSDs for mid-tier. SATA HDDs for capacity / backup tiers. Match drive interface to RAID controller; mismatches force fallback to lowest common denominator.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (40 votes · 42,601 views) ›
MegaCli: Get the /dev/sd* device name for a logical drive
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
Interface selection: NVMe (PCIe Gen4/5) for random workloads above 500 IOPS. SAS SSDs for mid-tier. SATA HDDs for capacity / backup tiers. Match drive interface to RAID controller; mismatches force fallback to lowest common denominator.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (19 votes · 43,208 views) ›
How effective is LSI CacheCade SSD storage tiering?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (24 votes · 18,189 views) ›
Differences between HW RAID and ZFS
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
Interface selection: NVMe (PCIe Gen4/5) for random workloads above 500 IOPS. SAS SSDs for mid-tier. SATA HDDs for capacity / backup tiers. Match drive interface to RAID controller; mismatches force fallback to lowest common denominator.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (11 votes · 42,108 views) ›
Suddenly slow RAID performance
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
Disk I/O observability: iostat -xz 5 for per-device throughput, iotop for per-process I/O attribution, dstat for combined dashboards. For long-term capture, push node_exporter output to Prometheus.
Drive cloning: prefer partclone or clonezilla over raw dd when the drive is mostly empty — they only copy used blocks. Append conv=sparse to dd to skip zero-filled regions at the destination.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (18 votes · 17,655 views) ›
How can I get an email alert when RAID array is degraded? VMware ESXi 5.0, MegaRAID SAS 9260-4i
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
Interface selection: NVMe (PCIe Gen4/5) for random workloads above 500 IOPS. SAS SSDs for mid-tier. SATA HDDs for capacity / backup tiers. Match drive interface to RAID controller; mismatches force fallback to lowest common denominator.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (11 votes · 24,577 views) ›
LSI MegaRAID Expected Chip Temperature?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (6 votes · 33,217 views) ›
MegaRAID JBOD substitute
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (9 votes · 24,473 views) ›
Managing battery relearn cycles on LSI and similar RAID controllers
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
SMART monitoring: alert on attributes 187 (reported uncorrectable errors), 197 (current pending sector count), and 198 (offline uncorrectable count). Non-zero values typically indicate 30-90 days of remaining service life.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (13 votes · 14,300 views) ›
Configuring RAID 10 using MegaRAID Storage Manager on an LSI 9260 RAID card
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
Interface selection: NVMe (PCIe Gen4/5) for random workloads above 500 IOPS. SAS SSDs for mid-tier. SATA HDDs for capacity / backup tiers. Match drive interface to RAID controller; mismatches force fallback to lowest common denominator.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (6 votes · 28,248 views) ›
Samsung 840 Pro SSDs in a Dell R720
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
Interface selection: NVMe (PCIe Gen4/5) for random workloads above 500 IOPS. SAS SSDs for mid-tier. SATA HDDs for capacity / backup tiers. Match drive interface to RAID controller; mismatches force fallback to lowest common denominator.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (8 votes · 23,179 views) ›
LSI Megaraid alarm - clearing hotspare
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Array rebuild planning: RAID 6 rebuild on 12-drive 4TB array typically takes 24-48 hours. Schedule monthly consistency checks (mdadm --action=check on Linux) to catch latent errors before they trigger a rebuild.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (9 votes · 19,505 views) ›
What's a "battery relearn" on a LSI MegaRaid?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
UPS sizing: 5-15 min runtime with generator backup, 30-60 min for sites without. Online double-conversion UPS for production workloads. Replace RBC batteries every 3-5 years. Monitor health via SNMP.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (6 votes · 22,424 views) ›
LSI RAID: Write cache policy affects read performance?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
Interface selection: NVMe (PCIe Gen4/5) for random workloads above 500 IOPS. SAS SSDs for mid-tier. SATA HDDs for capacity / backup tiers. Match drive interface to RAID controller; mismatches force fallback to lowest common denominator.
iSCSI / FC LUN scanning: from Linux iscsiadm -m discovery + iscsiadm -m node --login; on Windows, refresh in iSCSI Initiator. Rescan SCSI bus with echo "- - -" > /sys/class/scsi_host/hostN/scan.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (7 votes · 19,812 views) ›
How to create Raid 10 with megacli
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (8 votes · 17,195 views) ›
Just installed LSI 9211; no drives showing up to Linux
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (6 votes · 19,707 views) ›
Dell R730xd - Best way to configure storage for simultaneous use with ZFS & Hardware RAID
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
Interface selection: NVMe (PCIe Gen4/5) for random workloads above 500 IOPS. SAS SSDs for mid-tier. SATA HDDs for capacity / backup tiers. Match drive interface to RAID controller; mismatches force fallback to lowest common denominator.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (11 votes · 7,852 views) ›
Does enabling JBOD mode on LSI based controllers affect existing logical disks/arrays?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
Interface selection: NVMe (PCIe Gen4/5) for random workloads above 500 IOPS. SAS SSDs for mid-tier. SATA HDDs for capacity / backup tiers. Match drive interface to RAID controller; mismatches force fallback to lowest common denominator.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (8 votes · 12,549 views) ›
How do I extend a RAID5 array with storcli?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (7 votes · 14,274 views) ›
Recover from a Punctured RAID array
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Array rebuild planning: RAID 6 rebuild on 12-drive 4TB array typically takes 24-48 hours. Schedule monthly consistency checks (mdadm --action=check on Linux) to catch latent errors before they trigger a rebuild.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (11 votes · 5,993 views) ›
Do I need to initialize a MegaRAID virtual disk after adding it?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (6 votes · 14,358 views) ›
RAID level confusion (MegaCli vs megasasctl output)
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
Interface selection: NVMe (PCIe Gen4/5) for random workloads above 500 IOPS. SAS SSDs for mid-tier. SATA HDDs for capacity / backup tiers. Match drive interface to RAID controller; mismatches force fallback to lowest common denominator.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (6 votes · 12,313 views) ›
How to install ZFS on Dell Poweredge server and Dell disk array without using the RAID controller
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
LSI 9285-8e and Supermicro SC837E26-RJBOD1 duplicate enclosure ID and slot numbers
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
Interface selection: NVMe (PCIe Gen4/5) for random workloads above 500 IOPS. SAS SSDs for mid-tier. SATA HDDs for capacity / backup tiers. Match drive interface to RAID controller; mismatches force fallback to lowest common denominator.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Why is my RAID1 read access slower than write access?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
Drive cloning: prefer partclone or clonezilla over raw dd when the drive is mostly empty — they only copy used blocks. Append conv=sparse to dd to skip zero-filled regions at the destination.
Interface selection: NVMe (PCIe Gen4/5) for random workloads above 500 IOPS. SAS SSDs for mid-tier. SATA HDDs for capacity / backup tiers. Match drive interface to RAID controller; mismatches force fallback to lowest common denominator.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Original question on Server Fault (10 votes · 3,265 views) ›
FIO Benchmarking - Inconsistent and Slower than Anticipated: Are my RAIDs Misconfigured?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
The answer depends on your specific platform, workload, and operational requirements. For environment-specific guidance, email sales@prodisknetwork.com with your server model and target configuration.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Is there a linux monitoring utility for Dell PERC H700?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
Interface selection: NVMe (PCIe Gen4/5) for random workloads above 500 IOPS. SAS SSDs for mid-tier. SATA HDDs for capacity / backup tiers. Match drive interface to RAID controller; mismatches force fallback to lowest common denominator.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
Linux: ZFS analog of pvmove - how to move data off from vdev?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
Interface selection: NVMe (PCIe Gen4/5) for random workloads above 500 IOPS. SAS SSDs for mid-tier. SATA HDDs for capacity / backup tiers. Match drive interface to RAID controller; mismatches force fallback to lowest common denominator.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
How is LSI FastPath different from Software RAID?
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
STP / RSTP / MSTP: use RSTP (802.1w) over legacy STP for sub-second convergence. MSTP (802.1s) maps multiple VLANs to fewer spanning-tree instances. For modern leaf-spine fabrics, replace STP with BGP-EVPN underlay (no loop possible because no L2 forwarding between leaves).
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
RAID1 and RAID6 arrays disappeared in Dell PERC6, all disks are listed as available
RAID controller questions usually involve hardware-vs-software, firmware mode, or cache strategy.
RAID level guidance: for HDD arrays of drives 4 TB or larger, use RAID 6 (dual parity). RAID 5 is no longer responsible at large drive sizes — the rebuild window exceeds typical MTBF. RAID 10 (stripe of mirrors) wins for OLTP databases and VDI write caches.
Interface selection: NVMe (PCIe Gen4/5) for random workloads above 500 IOPS. SAS SSDs for mid-tier. SATA HDDs for capacity / backup tiers. Match drive interface to RAID controller; mismatches force fallback to lowest common denominator.
HBA firmware mode: IT-mode (pass-through) is required for software RAID (ZFS, vSAN, Ceph). RAID-mode for hardware RAID. LSI/Broadcom 9300/9400/9500 series HBAs flash between modes cleanly.
Pro Disk Network ships LSI / Broadcom / Adaptec / Dell PERC / HPE Smart Array controllers. RAID buying guide · Storage controller catalog
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