This section describes several issues that may prevent a Windows server from successfully booting from a SAN:. A very common problem when you configure a SAN is that it is possible that multiple hosts may have access to the same logical disk.
This usually occurs because proper LUN management was not employed. The default behavior of Windows is to attach and mount every logical unit that it detects when the HBA driver loads. If multiple hosts mount the same disk, file system damage can occur. It is up to the configuration of the SAN to insure that only one host can access a particular logical disk at a time. Symptoms of multiple hosts accessing the same logical disk are:.
Disk Management displays the same logical disk on multiple hosts. Plug and Play notification that new hardware is found may occur on multiple hosts when you add or configure a new logical disk. When you try to access a logical disk by using My Computer or Windows Explorer, you may receive an "Access Denied", "Device not Ready", or similar error message that may indicate that other hosts have access to the same logical disk. Your computer stops responding hangs or has slow response times.
This can indicate that there is a high latency to the pagefile, and this may be accompanied by events in the System Log such as:. If the preceding error messages are in the System Log, it indicates that Windows was trying to access a disk and there was a problem. If the disk that is referenced is on the SAN, it could indicate a latency issue.
If an Event ID 51 is shown, this indicates that Memory Manager was attempting to copy data to or from memory and had a problem. Another indicator of pagefile latency issues is if the Windows server has a system failure, and either of the following error messages are displayed on a blue screen:. A possible resolution is to place the pagefile on the host's local hard disk. Windows needs reliable access to the pagefile as data is paged in or out of memory.
Having the pagefile local to the host guarantees that access is not influenced by other devices and hosts on the SAN. A Memory. For information about how to configure your computer for a crashdump, see Windows Help.
There are several ways to resolve the preceding problems. The first method is to try and correlate the time with any events that are occurring on the SAN. CrystalDiskMark is a tool for benchmarking the performance of storage devices and issues with MariaDB is an open source relational database management system. This article shows how to MySQL is one of the most popular relational databases.
MariaDB is a fork from Purely Technical. Steps 1. Related Stories. QLC vs. In diskless server builds to reduce power consumption by having no internal disks. Benefits: Minimize system downtime, perhaps a critical component such as a processor, memory, or host bus adapter fails and needs to be replaced.
Enable rapid deployment scenarios. Boot from SAN alleviates the necessity for each server to have its own direct-attached disk, eliminating internal disks as a potential point for failure. Thin diskless servers also take up less rack space, require less power, and are generally less expensive because they have fewer hardware components. Centralised management when operating system images are stored on networked disks, all upgrades and fixes can be managed at a centralized location.
Changes made to disks in a storage array are readily accessible by each server This includes benefits in capacity planning as you typically have a holistic view of your SAN environment. If a disaster destroys functionality of the servers at the primary site, the remote site can take over with minimal downtime. Recovery from server failures is simplified in a SAN environment.
With the help of snapshots, mirrors of a failed server can be recovered quickly by booting from the original copy of its image. As a result, boot from SAN can greatly reduce the time required for server recovery. Do you have enough physical capacity in your array to support this? This can be mitigated to some extent by moving page-files to local disks or installing more memory. Migrating OS to BFS in some situations can have a negative impact on the array or fabric switches potentially causing contention check ISL fan-in ratios.
Be mindful of boot storms after an outage or in VDI deployments, you may have to selectively boot tier1 apps in phases bear in mind tier 1 application dependencies such as DNS, LDAP or Active Directory servers, they need to be started first. Review your tier 1 app service dependencies and their IOPs requirements see point above for throughput considerations.
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