STORAGE MANAGEMENT TIPS

Storage area network (SAN) environments have evolved significantly in terms of aspects like performance, features, security and scalability. However, it's still essential to manage each SAN component separately, as the typical SAN consists of components such as the host bust adaptor (HBA), fiber channel (FC) switches and a storage system. Therefore, the following points should be considered while designing, deploying or administering a SAN to ensure optimal SAN management.

SAN Management Tweaks

SAN management tweak 1: The host operating system should be updated with latest HBA drivers. Also ensure that you update the HBA's firmware. We see many a time that performance increases considerably with updated firmware and HBA drivers. Storage connectivity problems are also resolved by updating HBAs with the latest firmware.

SAN management tweak 2: In case of SAN based backups, it should be noted that the HBA driver version remains consistent across all the SAN backup clients, as we may face recovery problems in case of directed recoveries and also in case of backups. In such cases, a backup client will be unable to read the data backed up on tape by the other client. Similarly, we may face errors that indicate a hardware error during backups and mislead us, as the problem lies with the inconsistency of drivers. I have seen these problems arising at many sites because of the inconsistency of drivers. So this issue should be taken care of while updating the HBA driver on each backup host. This SAN management best practice also applies to hosts accessing a common storage box.

SAN management tweak 3: It's best not to intermix FC switches and HBAs from different vendors in your SAN environment. Such mixing may lead to compatibility and performance issues.

SAN management tweak 4: It is recommended to always perform a single initiator zoning. Use only one initiator per zone.

SAN management tweak 5: Soft zoning (WWPN base zoning) should be preferred over hard zoning, since change in cabling of the fabric will not result in loss of storage access to hosts.

SAN management tweak 6: SAN topology also plays an important role with respect to scalability, resiliency, performance and security of a SAN. So the core edge SAN topology should be considered for building SANs. If there are two switches connected by an inter switch link (ISL) between them, then you should ensure that there is a minimum of two ISLs between them. The initiator and target ports should not be more than six per ISL.

SAN management tweak 7: In an iSCSI SAN, use a dedicated VLAN for storage traffic. Ensure that you use the latest ISCSI initiator version for respective operating systems, CAT 6 cables, and set iSCSI port settings to Ethernet full duplex. It has been observed that Ethernet port settings have a visible effect on the performance—full duplex settings have given best results on this front. When it comes to management of iSCI SANs, it's a good practice to use jumbo frames.

SAN management tweak 8: We have observed that storage administrators mostly deploy RAID 5 protection, which is suitable for most applications. But at times, RAID 5 may not suffice the requirements of applications which require high performance. IOPS requirements are quite high in such cases. So ensure that you use RAID 10 and if feasible FC Drives or EFD drives.

SAN management tweak 9: Most storage boxes contain two backend buses. So the disk array enclosures (DAE), load should be divided equally among the two backend buses. So if we have eight DAEs, then four DAEs should be connected through one bus and the remaining through the other bus.

SAN management tweak 10: Cache also performs a vital role in storage boxes' performance. It has been observed that arrays perform optimally when the read cache is set to 20% and write cache to 80% of the total cache.


LUN Management in SAN

Disk drives are the foundation of data storage, but operating systems cannot use physical disk storage directly. The platters, heads, tracks and sectors of a physical disk drive must be translated into a logical space, which an OS sees as a linear address space comprised of fixed-size blocks. This translation creates a logical entity that allows OSes to read/write files.

Storage networks must also partition their physical disks into logical entities so that host servers can access storage area network (SAN) storage. Each logical portion is called a logical unit number (LUN).

LUN basics
A LUN is a logical entity that converts raw physical disk space into logical storage space, which a host server's OS can access and use. Any computer user recognizes the logical driv...